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Dan5
08-06-2011, 22:07
New poster! (less than 10 posts)

Hi I bought a new 5 a couple of weeks ago it drove all the way from birmingham to scotland with no problems but about 50 miles from my house i was in a bit of traffic and notice the temp was going past the 3rd line on the gauge.

I managed to pull over and noticed the fan wasn't coming on so I disconnected the connector from the rad switch and bridged it. The fan came on so i left it bridged until i got home.
I bought and fitted a new rad switch and all was well until today when the exact samething happened :cry:
Is their something i'm missing?

Any help would be much appreciated.
James5
08-06-2011, 22:18
Rad fan relays tend to fail
J8TRO
08-06-2011, 22:19
I bought and fitted a new rad switch and all was well until today when the exact samething happened

from the above I presume you have replaced the temp sensor switch in the rad which the two wires connect to.

Check the relay in the circuit. It is found infront of the altenator normally clipped to the cowling on the front of the car if its still there. Black in colour, square body but circular connection.
old skool turbo power
08-06-2011, 22:49
New poster! (less than 10 posts)

Hi I bought a new 5 a couple of weeks ago it drove all the way from birmingham to scotland with no problems but about 50 miles from my house i was in a bit of traffic and notice the temp was going past the 3rd line on the gauge.

I managed to pull over and noticed the fan wasn't coming on so I disconnected the connector from the rad switch and bridged it. The fan came on so i left it bridged until i got home.
I bought and fitted a new rad switch and all was well until today when the exact samething happened :cry:
Is their something i'm missing?

Any help would be much appreciated.


check the thermostat in the top hose from the water pump if it has one?when the thermostat opens it will let in hot water into the rad and then the 2nd thermostat in the rad should make your fan kick in.so check the thermostat as well,they could be the issue???id say.
Dan5
08-06-2011, 22:53
New poster! (less than 10 posts)

Yeah it was the rad temp sensor switch i replaced.

When i bridge the 2 wires on the connector the fan comes on if it was the relay would this still happen?
jamie_clioGTT
08-06-2011, 22:55
dont think it would if it was relay. check thermostat.
Dan5
08-06-2011, 22:58
New poster! (less than 10 posts)


check the thermostat in the top hose from the water pump if it has one?when the thermostat opens it will let in hot water into the rad and then the 2nd thermostat in the rad should make your fan kick in.so check the thermostat as well,they could be the issue???id say.

I thought that might have been the problem so went to check the thermostat and its not got one
old skool turbo power
08-06-2011, 23:20
New poster! (less than 10 posts)



I thought that might have been the problem so went to check the thermostat and its not got one


it always baffels me on when ppl never fit them or even if they think its that the problem they remove it never replace it with a new one yet they had dug out the old one :confused:.id refit a new thermostat in the top hose,make sure the rad thermo switch is all good in the rad as well and the conector,then warm the car up till the 2nd guage or just above and wait for the fan to kick in.if not then is electrical,bit long winded but least u know its one or the other.:agree:cooling has got to be 100%:)good luck mate.
tiff_lee
09-06-2011, 00:27
This doesn't entirely make sense, if there is no thermostat fitted then the engine temperature would be uniform across the whole lot, engine and radiator it's not as if the stat has failed to open causing temperature to rise.

Yet when you short out the connector to the radiator fan switch the fan runs which proves the fan/relay is working only leaving the rad fan switch itself as the fault.

When your engine is up to temp is it uniform across the radiator? because unless it is particularly cooler where the rad fan switch is I would say the replacement is a duff one.
TNT ANDY
09-06-2011, 06:43
Dan, what what temp range does your rad switch have? and what temp is your new engine stat?

if the fan runs when you bridge the 2 wires @ the rad stat then the relay etc is all ok so no need waste time there.

I've just changed my engine stat to an 89 deg C item as my temps seem a little low (this is a bad thing btw) and what should happen is that once the engine gets up to 89 deg C then the stat opens sending hot coolant to the rad. The rad switch will then see > 83 deg C (the upper value on that stat) and start the fan thus cooling the coolant. once the coolant reaches the lower value of that stat / switch it will have cooled all the coolant to that temp and the engine stat will have closed. The coolant will start to heat up again and the cycle will begin again.

Put a new rad switch in and get a thermostat in the engine - job sorted.
Bigfoot
09-06-2011, 07:31
Yet when you short out the connector to the radiator fan switch the fan runs which proves the fan/relay is working only leaving the rad fan switch itself as the fault.

Or that there is an air lock in the radiator/ or water not pumping round to the rad. On my car when you bridged the the rad fan swtich the fan came on, had to bleed the car after running for a while, took a few attempts to get all the air out but in the end the fan cut in.
TNT ANDY
09-06-2011, 09:28
Or that there is an air lock in the radiator/ or water not pumping round to the rad. On my car when you bridged the the rad fan swtich the fan came on, had to bleed the car after running for a while, took a few attempts to get all the air out but in the end the fan cut in.

good call.:agree:
tiff_lee
09-06-2011, 09:42
When your engine is up to temp is it uniform across the radiator? because unless it is particularly cooler where the rad fan switch is I would say the replacement is a duff one.
^^ like I said ;)
tiff_lee
09-06-2011, 09:58
Or that there is an air lock in the radiator/ or water not pumping round to the rad. On my car when you bridged the the rad fan swtich the fan came on, had to bleed the car after running for a while, took a few attempts to get all the air out but in the end the fan cut in.

Yeah with regards to bleeding open up the nipples (ohh) one at a time and get your lips round the header tank and give it a good blow (double ohh)!
Dan5
09-06-2011, 18:44
New poster! (less than 10 posts)

I'll have a go at bleeding the cooling system again. I think I'll also fit a thermostat into the top hose.

Thanks for your help:agree:
tiff_lee
09-06-2011, 19:37
To be fair though IMO if your radiator was airlocked then having the fan on or not would of made no difference and the car would of still overheated, the fact that having the fan running prevented overheating would indicate there was indeed water flowing through the rad.....

Again having no thermostat will not stop your fan coming on!
Dan5
09-06-2011, 22:13
New poster! (less than 10 posts)

Ok so I bled the cooling system let it heat up and the fan kick in on the 3rd line on the gauge. The engine cooled down to just over the second line but when it got back to the 3rd line again the fan didn't kick it. I'm thinking it's a dodgy rad fan switch I've got so I'll have to buy another one
TNT ANDY
09-06-2011, 22:25
New poster! (less than 10 posts)

Ok so I bled the cooling system let it heat up and the fan kick in on the 3rd line on the gauge. The engine cooled down to just over the second line but when it got back to the 3rd line again the fan didn't kick it. I'm thinking it's a dodgy rad fan switch I've got so I'll have to buy another one

Are there any local member that can lend you one?
Dan5
09-06-2011, 22:35
New poster! (less than 10 posts)

I don't think so I think I'm the only one up here. I'll borrow the one from my other 5 and see if that works any better
TNT ANDY
09-06-2011, 22:49
LOL even better
:agree:
old skool turbo power
11-06-2011, 17:13
New poster! (less than 10 posts)

I don't think so I think I'm the only one up here. I'll borrow the one from my other 5 and see if that works any better


personally mate id just order a brand new one if your not to fussed about time in getting it sorted out,least its brand new and you know its 100%.cgb,or mike phase 1 spares:agree:bleed car and then warm up car:)
Dan5
14-06-2011, 21:59
New poster! (less than 10 posts)

Today i fitted a new stat and rad temp switch. I then bled the cooling system waited for the fan to kick in it didn't. so I bled the system again waited for it to get to temp and this time the fan kicked in.

I thought I finally had it so took it for a drive. Everything was fine until i got home and had the same problem all over agian :cry:

Could it be that i have a air lock? or is there something else i should be looking at?
tiff_lee
14-06-2011, 23:53
How are you bleeding the system? blow into the header tank (i.e get your lips round the opening) and undo one bleed nipple at a time till squirts out.

If you let the car idle upto temperature and the fan doesnt start unplug it at the rad fan switch again and short the plug out to see if it starts as it may be an intermittent problem with the control/power circuit for the fan.

However if it does start as soon as you short the plug out then the problem is your rad/fan switch isn't closing its contacts which is either because the switch is fubar (been replaced what twice now? so unlikely) or it isn't getting hot enough, what is the temperature like across the radiator hot/cold? does it reflect what the temp gauge is telling you.