RTOC RENAULT 5 GT TURBO BUYING GUIDE

This month the buying guide is on that cult Hot Hatch the Renault 5 GT Turbo. Back in the late 80’s & early 90’s these cars were many young man’s dream and were slugging it out with Peugeot 205 & VW Golf GTI’s around every ring road & leisure centre car park. There have been many buying guides for these cars over the years, giving differing recommendations on what’s right & wrong. However this time the Renault Turbo Owners Club (www.rtoc.org) has created a buying guide to ensure that you are provided with the most accurate and comprehensive guide so far.

Over the last 25 years the Renault 5 GT Turbo has maintained it’s appeal to many car enthusiasts from those continue to compete and win in various racing series to those who want a small fast hatchback with great engine and chassis tuning potential to those who enjoy it as a styling icon for hot hatches with modification from the sensible and practical to the exaggerated extreme.

The inherent appeal of these cars is the lightweight nimbleness coupled with great driver feedback and it’s ability to put a huge smile on anyone’s face when the turbo comes on boost.

Many people remember the big wheels & excessive body kit scene of the nineties, epitomised by the Ali G film in 2002, but think that looks ridiculous with actual performance loss and there has been a shift in restoring cars back to factory fresh original looking examples as illustrated by Big Steve’s concourse winning Raider pictured here.

HISTORY

The Renault 5 was launched in 1972 and spawned many performance versions from the Turbocharged Alpine (named Gordini in the UK), to the rear wheel drive wide bodied Turbo in 1980 that won the 1981 Monte Carlo rally, the Turbo II in 1983 and the Maxi in 1985 of which only 20 were made. In total only 5007 T1, T2 and Maxi were made.

The second generation Supercinq (Super Five) was launched in 1985 and was styled by Marcello Gandini who had previously penned the Lamborghini Countach. The chassis was based on the Renault 9/11 models with McPherson strut front suspension and transverse engine and gearbox, but the Renault 5 styling trademarks were retained.

When the Supercinq was launched the GT Turbo was not offered for sale but was included in the brochure as the “Coupe” model. This Coupe model was described as being developed for racing only and not available for sale, but by 1986 the GT Turbo was launched with a price tag of £7,710. Producing 115bhp, it was fitted with a slightly different body kit to the one shown here.

In 1987 Renault made a number of small but significant changes and designated it the phase 2 model. Most obvious was the painted and smoothed body kit that reduced the car's drag coefficient from 0.36 to 0.35, different wheels and seat cloth, and a more comprehensive centre console. Under the bonnet were some improvements to address the Phase 1 hot starting problems; • an Anti Percolation Fan to cool the carburettor, and when the engine is off, to cool the turbo compressor and also intercooler when it’s thermostatically controlled diverter flap is open, • a water cooled turbo charger and re-routing of some of the cooling system pipes. An ignition map change increased the power by 5 BHP to 120 BHP. To prevent heat damage the electronic ignition unit was relocated from above the turbo to behind the bulkhead. In 1990/91 the throttle cable to the carburettor was re-routed, the steering column rubber UJ was replaced with a metal one, the door cards were given a corduroy cloth cover, additional sound proofing and a light were added to the boot. In late 1991 the 5 GT Turbo was discontinued making H plates the last available although there are a few J and K registered cars around, these just cars stored by Dealerships and sold at a later date. The special edition 'Raider' 5GTT is a phase two with just some colour changes and no extra power. There were no 1.7 litre 5GTTs. There is a comprehensive list of the differences between phase one and phase two at the RTOC website.

There are approximately 3500 GT Turbo’s still registered with the DVLA and with the newest cars now 20 years and as Renault discontinue parts they are becoming harder to source. However, due to the fanatical following and a number of specialists, there are few parts that are truly unobtainable.

Advice

When looking at a potential 5GTT to purchase, bear in mind the cost of buying for what seems like a bargain vs. the cost of making and keeping it road worthy.

Don't buy one unless you know what faults to look for or know someone who does as very often the car will need specialist work be it mechanical or cosmetic.

BODYWORK

The Supercinq was one of the first new Renaults in the 1980’s to be fully treated to a 5 stage anti corrosion process and they've lasted fairly well but there are a few common areas for rust to watch out for. As with all older cars it pays to get it on a ramp to have a good look underneath.

Main areas to check are the outer sills, hidden behind the plastic sill extensions, the inner sills and the front jacking points which are an MOT fail. Thankfully all of these parts are available from Renault or third party panel suppliers, budget up to £300 per side for a restoration repair as opposed to a much cheaper MOT repair which may have been done for a previous owner.

Common rusty areas are the front and rear bumper mounting points. As these are hidden by the bumpers and arches they can really only be seen with the bumpers removed. The RTOC has managed to source a number of repair panels which have been specially manufactured to replace corroded panels in these areas and they are available through their website.

Easy to see is around the bottom edge of the windscreen. The 5's bonded windscreen needs to be cut out of the car to be replaced and the removal process can cause scratches or damage to the paint underneath the bonding agent.Repair panels are no longer available from Renault leaving your only option a repair patch. You can check the condition of this area by running you hand under the lower windscreen area from within the scuttle area. There are two small drainage holes at each lower corner of the screen where corrosion usually starts.

Also check the floor panel drainage plugs, where it folds up around the fuel tank, and the boot floor where it meets the rear arches. Check the tailgate around the glass.

The front doors can drop and become difficult to close if their hinges are not kept lubricated as they corrode and wear away. This can allow the bottom corner of the door to catch the sill and promote rust. It’s common now to have to fit new hinge pins and bushes on the newer version doors or drill and fit specially made shims, not available as a spare part, on the older versions.

INTERIOR

The interior of the car is comfortable and ergonomic. GT Turbos were fitted with a black vinyl covered dashboard instead of the standard hard grey plastic. In general the whole interior is fairly hard wearing but the drivers seat outer side bolster foam breaks down. New bolsters are still available from Renault at a cost of around £80 but cheaper replacements are available on the internet and second hand.

If the front seats rock excessively on their mountings check the two pivot bolts that couple them at the front to their sub frames as they come lose and need tightening from time to time. Otherwise it can mean having new DIY bushes welded in.

Original gear knobs are no-longer available from Renault and command a premium price.

The electric windows are known for being slow, this is caused by motors with old dried out grease & perished rubber guides. Some time spent cleaning & re-greasing the mechanism can vastly improve the situation. The central locking motors are available cheaply second hand.

Sometimes the cause for slow windows and central locks is simply corroded electrical connectors. These fail to pass adequate current to operate the motors and replacement for new is required as cleaning has little or no effect.

Check the carpet checked for dampness as water can leak in through a rusting scuttle panel under the battery tray, around the windscreen if it’s come away from the bonding or rusted through, around the rear side windows and from under the doors cards if their inner mastic seal has not been re-applied. It can also track in via the door speaker baskets.

Coolant can leak out of the heater matrix. To replace this, the dashboard may have to come out and this was listed by Renault as a 10 hour job.

If the orange dial faces of the instrument panel are faded they can be changed for new replicas that the RTOC have had made and are available from their shop.

There are no air bags and no collision seat belt tighteners.

There is no air conditioning except for a 5GTT variant available only in Japan.

No sunroofs were fitted by Renault. They were all fitted by the dealership network after taking delivery of the cars. Some dealers gave the customer making the original purchase a selection from a couple of versions. They can leak and drip water into the car and onto the front seats and at least one version has no available replacement parts.

WHEELS & TYRES

The 5 GT Turbo was supplied with 5.5J 13 inch Speedline alloy wheels and specifically manufactured 195 55/13 Michelin MXV Tyres. This custom sized tyre is now only supplied by Uniroyal in restricted numbers so some people fit 185/60 sized tyres instead which can degrade handling and does not give the same look to the car.

Many people fit 15” wheels, often from a Clio or with similar offset of about -35mm, and 195/45/15 tyres, which are about 10mm more in overall diameter to the originals, or fit less expensive 195/50 tyres. 15" wheels and lower profile tyres can sharpen the steering, increases the turn in bite and general grip for better braking and reduced wheel spin. They do make the ride 'bumpier'.

Whilst the radius with 195 45 15 is only about 5mm more than with the original wheels, height at the front from hub to the road is 10mm more due to less tyre squash than the original. It's 5mm higher at the rear. Lowering is in normally done just to get down the original ground clearance.

15" wheels also allow the fitting of bigger brake discs.

BRAKES

The standard brake set up uses single pot Girling callipers and 238mm vented disks and is quite adequate for both standard and mildly increased power outputs. The rear brakes use solid discs with Bendix callipers that can be found on some Citroens and Peugeots of similar age to the 5GTT and are moderated, depending upon the passenger load, by a compensation valve which is positioned in front of the rear axle. The hand brake works on the rear discs through the same pads as the foot brake. To change it's cable usually requires the removal of both rear callipers. There is an adjuster under the car to the correct handbrake lever height.

Ideally, check before buying that the discs are not rusted over and the front discs vents are not occluded by rust, the pistons and guides in all four callipers are free and the bleed nipples are not snapped off. Check the rear callipers pad retaining bracket is moving and not seized by rust or the pads don't press on the discs which rust over. Check that the spring tensioned compensation valve is free to move. This can seize causing insufficient rear braking but often can be freed with the help of some Plus-Gas.

If the seller can't demonstrate the recent age of the brake fluid it should be replaced as it can cause brake fade and the water in it can corrode parts such as the master cylinder.

Check the flexible brake lines for damage and age. Old original rubber lines should be renewed as they bulge under braking and can give a very soft pedal feel and not immediate enough braking. Use either new rubber lines or steel over braided PTFE lines.

Components are relatively low cost except for the brake servo unit at around £250 and the proportioning valve at £130.

With 15” and larger wheels, it's popular to fit larger diameter 285mm front discs together with calliper extender brackets. You won’t need to worry about fitting better callipers.

Big front discs are fitted for several reasons, for show, for less pedal pressure, for better for cooling but it’s not realistically possible to fit larger rear discs and this can lead to an imbalance of braking with too little from the rear tyres and poorer stopping. This is due to the extra leverage from extra diameter front discs leading to less pedal effort to lock the front wheels so the rears are simply doing proportionally less unless the rear compensator is turned on further by adjusting the rod toward the front of the car.

Don’t let larger front discs put you off even though many consider them unnecessary.

STEERING

There is no power assisted steering in the 5GTT although some other models do have it. This can make it hard work to park this car.

Is there play in the steering of a car you are viewing? There could be several causes. If the steering wheel has lateral or longitudinal play that would probably be the two ball bearing bushes in the upper column.

On pre H reg 5 GTT’s there was a rubber lined universal joint at the bottom of the steering column which wears out causing excessive play in the steering but it's fairly quick and easy to change.

If the steering wheel is rubbing on the fascia then it's been re-fitted too low but it's easy to adjust back to it's correct height. This can also cause the steering lock to jam on and not be released by the ignition key.

Steering racks are generally OK but can have play in the rack and pinion which can often be can be removed by adjusting the rack damping plunger; this requires rack removal.

The track rod ends can wear at a faster rate if hard springs, shocks and lower profile tyres are fitted.

SUSPENSION

The Supercinq was a big advance compared to the old R5. At the front; McPherson struts with an anti roll bar. At the rear; trailing arms with torsion bars and anti roll bars.

Many people felt the original suspension from Renault was not very good as when cornering the car tended to skip sideways on the very soft walled tyres with one end then the other, then one end, then the other gripping, rolling then stepping out, often with the rear rolling and skewing excessively then pulling the front. The car was easily and excessively unsettled by minor bumps and hollows. Renault used soft springs and a hard bump setting on the shock absorbers. This altogether, despite the soft tyres smoothing micro bumps during motorway cruising, gave a both hard ride and made for a difficult and unpleasant drive.

Most of the cars on the market will have been fitted with some form of non original suspension and will have been lowered. Check for cut down standard front springs, leaking shocks, and play in outer ball joints. Also check for play in front wheel bearings as with harder springs and lower profile tyres they can need replacement is as little as 12,000 miles. Any knocks or rattles on a test drive should be investigated and used as a negotiating point over price.

Often the front strut top mounts rubber 'doughnuts' squash and cause play both in the strut, which moves around, and in the steering when driving and can cause the rear of the car to sway side to side at speed making it difficult to steer in a straight line. If left uncorrected the metal strut top mounting plates can wear away and are longer available new. Refurbished parts are still available.

Wishbone and anti roll bar bushes are also prone to wear on hard driven cars and make the steering imprecise especially at speed and during braking. However original and polyurethane replacements are available.

The car responds well to the fitting of a front strut brace as it will steady the car during hard cornering, view this as a bonus if included in the sale.

Camber adjusting bolts are sometimes fitted to the front to try and provide more grip for cornering by adding more negative camber but can cause inner edge tyre wear. So on any lowered car check that there is not excessive negative camber. 1 – 1.5 degrees negative camber is normal.

If the inner edge is worn this can also be caused by incorrect tracking.

A well maintained car will have had a quality spring and damper combination fitted by now. The most popular is a Koni ‘yellow’ shock absorber and spring kit which retails for around £400. Different to what one might expect, the Koni kit gives a softer ride than the original equipment even though it eliminates the ‘boaty’ handling and replaces it with taught and driveability.

The supplied springs are often just for lowering but using at least 175lb per inch springs will dramatically improve the turn in and general cornering and 250 lb/inch is a lot better again although the ride is somewhat bumpier but possibly still less harsh than the OE. Some people are using 300lb/inch with re-valved Konis.

The front suspension geometry is designed to keep both front tyres flatter to the road surface while the car rolls; the outer wheel gains more camber and the inner wheel loses some. Lowering the front can adversely affect this, reducing the grip and upsetting the handling. Fitting harder springs might reduce this by reducing the roll.

If when you press down on the car wings to check the shock absorbers you find there is almost no movement, it could be the the car has been fitted with some very stiff 'coil over' shock absorbers. These can be too stiff for road use and can hurt your back and jar you internal organs. Owners fit them for appearance because they allow the ride height to be lowered further than can otherwise be done. Sometimes it's to have suspension that barely moves at all as some owners perceive this to confer a performance improvement for cornering of flat smooth roads. Whilst this can be the case with high quality shock absorbers that still do move over bumps, these low quality one simply make the ride unbearable and can also wear out quickly so you may have to budget for new shock absorbers.

Lowering the rear is accomplished by partially removing, turning and refitting the rear torsion bars. If you plan to make any changes to the offered cars ride height investigate when they were last removed as they commonly seize and require lots of work to free them up. You can quickly check condition by removing the black plastic cap on the end of the rear beam under the arch, any corrosion or a damaged thread into the torsion bar and you may have to replace the beam, lots of copper slip is a good sign.

It's very common for owners to lower the rear onto the bump stops of the shock absorbers as it's felt to improve the cornering on smooth roads. Apart from making the ride painfully hard at speed over bumps and bouncing the rear sideways, this quickly damages the rubber stops which can break away leading to shock absorber damage, leaking and the requirement to be replaced. Shorter shocks with more progressive bump stops are available.

Some people feel that with the small standard sized wheels the cars look as though they have too much arch clearance and like to lower the cars to improve the look; Steve’s car pictured here is lowered by 35mm at the front.

ENGINE

The Renault 5 GT Turbo uses a heavily modified four cylinder, eight-valve “Cléon” (or C Series) 1397cc engine. The unit is a Pushrod OHV design that can trace it’s roots back to 1962. To cope with the rigours of turbo charging, it was fitted with hardened valve seats, the compression ratio lowered 7.9:1 and heavy duty pistons with a 13mm crown thickness. The engine uses wet liners in a cast iron block meaning that the entire piston & liner assemblies can be changed without removing the engine from the car. The C1J engine is what gives this car much of its character.

The phase one 5GTT has the electronic ignition mounted over the turbo. This is not good as the heat damages it and it's likely to either be faulty or about to become so, causing the idle speed to continuously vary up and down and detonation can occur on less than full boost. In later models Renault moved it to behind the bulkhead.

A common misconception is that the engine and particularly the head gasket is unreliable. In reality quite the opposite is true if a few golden rules are followed. This bad press came about because owners in the 90s were increasing boost pressure without adjusting the fuelling within the carburettor resulting in detonation and H/G failure. An engine that has had vaguely regular servicing and maintains a good oil pressure will easily survive to 150k miles before rings, main bearings or valve guides need replacing, even when run well above standard boost. Many RTOC owners run 20 year old, totally standard engines up to 180 BHP for every day use without any problems and 200+ BHP is also easily achieved with mild cams and even bigger turbos. The key to reliability is in accurate fuel set-up, and using super unleaded to prevent detonation.

When buying check what boost is being used and ask lots of questions about the fuelling set up, a knowledgeable owners club members car will have had lots of attention in this area. A wide band lambda sensor and gauge is essential for any car running a bar of boost or more and should not put you off. Once set up you can remove this for an original look but remember to check fuelling regularly.

Always view the car started from cold. Make sure it idles correctly on the choke with very little smoke, white condensation is fine. Once warm ensure the fan starts and stops automatically without the temperature going over the third notch on the dashboard gauge. Then take it for a drive and check for black or blue smoke on boost or when backing off the throttle. Ensure you drive for at least 15 minutes and on return check to see if the owner lets it idle to let the turbo spin down before turning it off – a very good sign. Whilst still fairly hot, remove the oil filler cap and oil dip stick to check for 'mayonnaise' and check that the coolant level in the header tank has not dropped too low and there is no 'mayonnaise' in the coolant; that's a bad sign! If the anti-percolation fan doesn’t start automatically do not panic, they are often temperamental and require regular attention to the loom, heat sensors and fan unit. Squealing or leaking from behind the water pump pulley means it needs to be replaced; replacements are cheap and easy to fit.

If the original anti percolation fan is worn it will be nosey when spinning. Very early ones were not fused and sometimes caught fire if they seized. Renault issued a recall and all should now be fused near to the fan. Often they are removed but they do help to prevent a hot engine stuttering when driving in slow moving traffic. A much quieter yet more powerful fan is one from a Renault Safrane.

Another popular modification is to simplify the breather system as with higher boost oil often makes it past the oil swirl pot and blows out from the various places, such as a dump valve, or becomes smoke from the exhaust. Some people leave all the pipes in place except the one into the turbo and instead take that to a catch tank, preferably fitted with an oil drain back to the sump. Others remove the whole lot and just use a pipe into a bottle. If the engine develops a fault and a lot crank case pressure occurs, without the catch tank oil drain, unless it 4 litres in volume, it will overflow and the engine might then seize.

Check all the coolant and breather pipes for damage, they can rub together and burst if not retained in the OE clips or have been cable tied together. Beige stains can be a sign of coolant leakage.

Check the two bleed nipples are in good order. Brass replacements are available for the plastic type plugs and are a wise investment. Silicone replacement hoses are another popular upgrade, however check for cheap Chinese copies which are inferior, SFS and Samco have a good reputation.

CARBURETTOR

To control the fuelling a Solex 32DIS single choke Carburettor is used rather than fuel injection. This is positively prehistoric compared to today’s modern cars which have sensors everywhere. However this simple set up means that the cars are easy and cheap to tune. Thanks to the advance in wideband lambda sensor technology it is easy to re-jet the carburettor to deliver the correct amount of fuel for an increase in boost pressure.

Group A and Group N are racing classes and genuine racing parts are extremely rare. The so called Group A Carb as sold by tuners is best avoided as they are often just a bored out venturi and some over sized jets which fuel excessively rich, especially at part throttle. Look for a car with a recently serviced carburettor that has had lots of attention paid to the set up.

Re-jetting of the Carb requires an detailed knowledge of which parts to drill out and by how much, otherwise you will ruin your carburettor, over fuel the engine and risk premature wear of the turbos bearings through petrol in the oil. A number of RTOC members have become very skilled in setting up the Carb’s and can tune them to give either big power or much improved fuel consumption, many of whom only charge a cup of tea for their services.

A common problem with the 5GTT is poor idling; this is usually down to a blocked idle jet, however it is possible for the base of the Carb to be warped and the throttle spindle seals to be ovalised and leaking air. Replacement carburettors are all 20 years old now and will require a minimum of a new seal and gasket kit available for approx £30. RTOC sell a comprehensive re-build kit through their on-line shop and have detailed re-build guides on the website.

TURBOCHARGER

The GTT was originally fitted with a Garrett T2 Turbo and runs 7 psi of boost. This offers a good mix of power and low turbo lag. It is possible to increase the boost pressure of the T2 Turbo up to an absolute maximum of 14 psi at the manifold with standard carb and cam.

If the car your viewing has increased boost pressure then it should be fitted with an extra pressure gauge to sense manifold pressure. This doesn't mean the car has been abused but that the owner has taken care to monitor the pressure level. Another good sign is an oil pressure gauge that senses the pressure just before the turbo as turbos are particularly sensitive to low oil pressure which can result in very fast bearing wear. A turbo is also sensitive to poor oil quality and to the engine being switched off immediately after hard acceleration or high speed and can jam due to the oil in it burning and setting hard in it's bearings. This results no boost pressure.

Continual grey smelly smoke from the exhaust often means the turbo oil seals are worn and will need to be replaced. It can but does not necessarily mean new turbo as there are several companies that can refurbish and rebalance for maybe £350 but the fee varies with what needs to be done.

Many cars are now fitted with a larger turbo, T25 or T28, enabling an increase in boost pressure to more 20 than psi. A favourite is a Tomcat specification turbo, not an actual Tomcat turbo from an old Rover. These larger turbos have a larger lag which means they are not so usable around town but the higher top end power means they are great for overtaking on country lanes and main roads.

Turbo roller bearings are hardy and give maybe 200rpm less lag, but are expensive. VNT turbos are becoming popular as they spool much more quickly but still offer the large turbo benefits of lower back pressure and higher boost.

Dump valves are fitted by car manufacturers to increase the longevity of the turbo by preventing a high pressure spike after the turbo when the throttle is suddenly closed. They are fitted by turbo car enthusiasts often just to make a loud noise as some designs vent to atmosphere rather than re-circulating the pressurised air back into the turbo inlet. They can wear and leak and result in low or no boost. Double piston dump valves are less common, more expensive but better as they keep some boost pressure in the pipes giving a faster initial response to opening the throttle. The 5GTT did not have a dump valve from new.

The boost pressure is controlled by air pressure pushing a diaphragm in a metal can attached to the turbo which pushes open a metal flap in the turbo known as a wastegate. This can is known as the actuator and the original ones have a soft spring inside which is not much use with higher boost as it's not enough to hold the flap fully shut so the boost is slower to build. Worse still is if a bleed valve is fitted to increase boost by bleeding off pressure to the diaphragm instead of the metal rod being wound on further to increase spring pressure. The correct fix is to fit a better actuator with a removable spring allowing one to be chosen to match the boost pressure you want. A favourite is the T3 style actuator with a spring rating designated -12.

Renault used a method of controlling the turbo wastegate actuator that many people remove. The modification is known as the "Cup mod" as it was the method used in the 5GTT Cup racing series. It removes some rubber pipes from the engine bay and results in a sharper boost response which many owners like.

EXHAUST

There are likely to be a variety of tailpipes emerging from under the rear bumper, or sometimes from the left side in front of the rear wheel. Some people think the look of the tail pipe is all that matters but the rest of the system is crucial to performance. Originally there was a tiny tailpipe and a quiet two silencer system with a sprung flexible coupling near the front joining to a thick walled pipe with narrow a bore going up to the turbo. The flexible coupling was fixed in place by a plate and a bar coupled to the engine block and often owners have not refitted these. No catalytic converter is required in these pre '91 cars.

There is a good deal of performance to be had from a well designed free flowing replacement system that does not contain a restrictor or a narrow bore silencer, apparent as a welcome increase in torque and reduction in turbo spool up time as a result of the lower back pressure after the turbo.

Also original equipment is a boost compensation system which senses the pressure rise in the original exhaust after the turbo and applies air pressure to the front part of the turbo actuator, closing the wastegate a bit and raising the peak boost pressure about 1psi. This does not function with a free flowing exhaust so the system of pipes that constitute it are often removed and certain holes plugged.

There are many replacement exhaust but the best for performance are the 2 1/4" or 2 1/2" full systems that are from the turbo backwards. These are usually stainless so will last well. If the seller is talking about a big bore exhaust make completely sure they are not just referring to the diameter of the tail pipe alone as this is meaningless apart from a small change in the noise.

It's not that unlikely now that the car will be fitted with a side exit exhaust. These are quite a bit louder both outside and inside the car. A good side exit may yield a small performance increase over a very good rear exit system but possibly only at very high boost and power levels. They are less expensive to buy and fit than a rear exit system and do pass the MOT.

COOLING SYSTEM

Any increase in the boost pressure/performance of the car puts more load into the cooling system which unless it is properly maintained will lead to the car overheating and again possible head gasket issues. The RTOC state that the standard cooling system is more than up to the job as long as it’s properly maintained. If the car seems to be running too hot it is probably a partially occluded radiator or a build up of silt within the system. Once the cooling system is fully thoroughly flushed out, and the water pump checked for a good flow rate most overheating problems will disappear otherwise the radiator will probably need to be replaced. Some replacement radiators made from copper were know to leak. For flushing only use water as some engine flushes have been known to block turbocharger waterways. The cooling fan should cut in as the gauge reaches the 3rd of 4 marks unless a low temperature fan switch is fitted where it will be about 1/2 a mark lower.

Some people remove the thermostat in the top radiator hose near the water pump in a vain attempt to help car run cooler, however this means the engine does not warm up fast enough and can cause cavitation within the water pump and erosion within the cylinder head. It’s better to use a lower temperature radiator fan switch. Some people like to drill a 4mm hole in the top of the thermostat to aid coolant system bleeding.

If there is white powder in the exhaust tail pipe this can mean an over heating engine possibly caused by blocked radiator.

There is an oil cooler built into the radiator to prevent the oil from over heating.

CLUTCH

The clutch on the 5 GTT is known for being quite stiff to actuate but should disengage before the pedal reaches the carpet. If you find yourself having to push the pedal almost through the floor of the car to disengage the clutch there is a problem. This first thing to do it to check the self adjusting mechanism is not jammed but moving freely. If it is jammed then free it by pulling it toward the drivers seat, it is only a simple ratchet situated just above the pedal.

Another cause might be a stretched clutch cable which could snap at any moment so should be replaced ASAP before you are left stranded. However if the release mechanism is fully functional it will take up the slack.

OE cables are much higher quality than pattern parts which frequently snap, particularly when routed incorrectly.

Early on Renault changed the clutch pedal design to what is often known as the ‘White’ pedal due to it having white plastic instead of black. This should have been fitted in the recall but many weren’t. This more or less eliminated the problem of the clutch cable snapping every 6000 miles or so.

There are two original clutch cables, one for the black pedal and one for the white. They are slightly different lengths. However it is difficult to tell which you have fitted, and even with the clutch centre plate worn to the rivets the pedal will be at the correct height if the self adjust is working properly.

For much above standard torque, the RTOC recommend the Valeo Volvo 480Turbo three piece clutch kit, it has sufficient torque capacity for all but the most powerful GT Turbos and is relatively cheap. When you are changing the clutch a sensible modification is to convert to the longer release lever and new pivot which will give you a softer clutch pedal with longer bite point and is much easier to use to feed in the power, especially on a wet road, and it also reduces the risk of snapped cables with this harder sprung clutch.

If the pedal is very hard to press and there is a sudden fierce bite this means a clutch such as the one mentioned above has been fitted but without the longer release arm. It not possibly to fit the arm without parting the engine and gearbox but some owners have welded an extension onto their existing arm.

The Group N clutch that you may have seen vendors selling is not an expensive special part but a standard clutch from another car. The Group A clutch will be a more expensive item and there are a few suitable parts around to make up something if the Valeo Volvo clutch torque capacity is not enough, e.g., if you’re making 230ft lbs, then the Valeo Volvo pressure plate can be used with a cerametallic paddle centre plate from AP racing or Helix, however these can cause judder on take up, badly wear the flywheel and not last long on a road car.

GEARBOX

The GT turbo gearbox is a JB series box. Phase 1s were numbered 014 and the Phase 2's were 032 and are fairly robust. They utilise an electronic Speedo pickup which can be prone to connection problems and means that the speedometer does not run or record the mileage. You should check that the gearbox shifts smoothly and that you can not hear any strange rumbling or whining during a test drive. A symptom of a tired gearbox is the fact that the car jumps out of 2nd, 3rd or 5th gear particularly when backing off the throttle which means the unit is worn, or the main retaining nut on the lay shaft is lose. If this is the case you will probably need a replacement gearbox or a rebuild. Don’t be fobbed off by the seller telling you that “they all do that” and all it needs is a change of the engine mounts or adjustment of the gear linkage rod.

Another problem which can happen to the JB series gearbox is that a large circlip on the passenger side of the unit can snap and the differential just spins leaving you without any drive. Thankfully it’s relatively easy to change and, as they fit all JB series gearboxes, are cheap to buy direct from Renault.

The 5GTT uses a JB3 and has the longest gears. Whilst it’s fine for plenty more then the original 120ft lbs, it can be a limiting factor for higher torque 5GTT’s. The bearings can fail after some time in moderately high powered cars. The JC5 box from a Clio has different bearings but there are conflicting reports as to their longevity when compared to the JB3. If torque is particularly high and traction is sufficient then the gears can instantly break as they are made from brittle cast iron. 1st gear is especially poor and the crown wheel can brake up and punch its way out of the casing. Its not uncommon to have the diff pop out of place if the retaining circlip becomes unseated. Sometimes tack welding this into place can fix it. Upgrading to a JC5 casing and bolt-in diff would be better.

JB5 is a 5 speed gearbox found on the NA's 5’s. It has a shorter case (bell housing to end cap) and narrower gears; and is much less strong than a JB3. JC5 is the Williams/172/182 unit and is the preferred gearbox, ratio's aside, because they nearly all come with a 4.07 final drive, which is a bit short for a typical GTT revving to 6500rpm. Put the final drive from the GTT's JB3 into a JC5 and you're onto a winner.

POWER/TUNING

The Phase 2 5 GT Turbo left the factory with 120 BHP which does not seem very high now compared to many modern cars, however as the car is very light at 830kg the power to weight ratio is quite high and a moderate increase in power can give impressive results. Many people strive to reach 200 BHP and to achieve this, the RTOC recommend the following modifications:

• Correctly re-Jetted standard venturi’d carburettor set for 20 to 25psi of boost.
• Free flowing exhaust with larger bore from the turbo back all the way through to the tail pipe. Not one with a restrictor or narrow baffle.
• T25 or T28 Turbo set to 20 to 25 psi; a favourite is the ‘Tomcat Spec’ not the actual Tomcat turbo. The larger the turbo the more power and the more lag.
• Stronger actuator, preferably the T3 type with a -12 spring.
• Actuator piping changed to the ‘Cup Racing Series’ Modification.
• Delete the rest of the boost compensation mechanism as it has no effect once a decent low back pressure exhaust is fitted.
• Boost gauge to read manifold boost pressure or you’ve no clue what boost you have as the OE dash gauge reads the pressure before the carb.
• Larger than OE intercooler with alloy welded on end tanks and generally front mounted.
• Different camshaft profile, a favourite is the 285 @ 110°.
• Stronger clutch, normally the Valeo Volvo 480T, with 'soft pedal' conversion.
• Firmer engine mounts to check the extra engine movement.
• Normally silicone boost hoses and new OE or silicone water hoses as old OE items tend to split. For reliability this applies even if you’re keeping standard power.
• Oil pressure gauge to show you the reading at the inlet to the turbo.
• Adjustable bracket for top dead centre sensor to allow timing to be backed off a few degrees.
• Bottom pulley from a Campus engine; it’s smaller diameter turns the alternator / water pump slower and doesn’t throw off the belt on sudden lowering of high engine rpm.
• For long term turbo reliability, not noise, a double piston dump valve, possibly re-circulating for no noise at all. Double piston as they keep the inlet pressure up when off boost giving more responsive get up and go.
• A crankcase breather oil catch tank will probably be required.
• Taking the inlet air from a cold place near the font of the engine bay through a decent flowing filter, possibly trumpeted.
• For reliability, new valve springs, possibly longer, harder and in lowered seats to match the taller cam. Possibly new collets. Possibly rocker faces over the valve stems reground to remove the edges worn by the standard cam. No need for valve seats, throats, ports, matching manifold at this power level, it will yield little power for the expense.
• NB: Modify at your own risk! This is not a detailed list, just basic guide. It's not the RTOCs fault if your engine fails after only a few minutes because you didn't understand what to do and didn't ask the right people the right questions!

To give you some idea as to how tuneable the GT Turbo is, the RTOC hold an annual Drag racing event every year at Santa Pod and the current ¼ Mile record holder, Glenn Robson, ran an amazing 11.2 second quarter mile in 2010.




Contributed by Ian Simpson.
11March 2011.
Ian S RTOC Profile