Cooling System Flush

[Woznaldo]

Before the flush my temp gauge was sitting at the top of the middle third and I wanted it to sit in the centre of the middle third. The radiator is a new std Renault Valeo unit.

Head gasket is newish and the coolant level hasn't moved since the gasket change so, no leaks.

After reading countless threads about flushing the coolant out, I thought i'd give it go to see if things improve.

I disconnected one hose from the header tank and let it drain, I then stuck a garden hose in the end of the disconnected hose and ran cold water through the system for 10 mins, by which time it was running clear. I then disconnected the other header tank hose and repeated the flush back the other way until the coolant was running clear.

Next I hooked up all the hoses back to the header tank and filled and bled the system with water only. I fired up the motor and let it get up to centre of the middle third on the gauge. I also noticed that at this point that the rad top hose and rad were cold. The thermostat didn't open until 4/5 up the middle third of the gauge?

Also noted that the rad fan doesn't kick in until top of middle third on the gauge?

Is the above normal for the rad fan and thermostat?

The engine has been drained again and is being given a couple of hours to cool before flushing with cold again.

[Andrew Cooke]

no amount of flushing will change when the stat opens, all it will do is stop the temperature creeping up once the stat has opened. The temperature indicator is just that, it's not a calibrated anything. If you want to go all "Duncan Grier" over it start by getting a decent gauge, otherwise don't worry about it until the gauge gets to the point where the fan kicks in when moving, or gets into the red stationary.

[Philclubman]

Get a new thermostate, for the price of them its worth getting a new one, they can easily become trouble, ive had them jam up, stop working and cause no end of trouble. Mine sits at the first mark and will go upto half way up the standard gauage at most,

[Guybrush]

Get a new thermostate, for the price of them its worth getting a new one, they can easily become trouble, ive had them jam up, stop working and cause no end of trouble. Mine sits at the first mark and will go upto half way up the standard gauage at most,

and don't bother with a low temp stat from the tuners... just get a standard one.... 83degrees i think.

[raj]

woz, just wondering have you also flushed the block via the blockdrain plug.? its worth doing it.
also as this was recommended to me- to aid bleeding,drill a 3mm hole on the edge of the stat.

[Woznaldo]

I've flushed it through again and flushed the rad too but, the result is the same. I think i'll get a new thermostat and go from there.

The car isn't road legal yet but, I want to make sure the cooling system is tip top before pushing hard in what could be 40 deg C ambient temps and up to 100% humidity this summer (UK winter).

I like the idea of the 3mm bleed hole in the thermostat.

Thanks for the advice.

[Big Steve - Raider]

Next I hooked up all the hoses back to the header tank and filled and bled the system with water only.

Hey Woz,

I thought that when you add antifreeze it helps the water exchange the temperature better???

Surely that's why they sell those watter wetters is it not?

Maybe if you try with a bit of antifreeze it may be better??

Steve

[Woznaldo]

Hi Steve,

It was filled with the correct mix of anti-freeze, I only used the water only route as I knew I was going to flush the system twice and didn't want to waste it.

The system is at the correct mix at present and it's still the same.

[michael tierney]

my current and previous 5 only went to half way on the guage but i did have a blocked rad at one stage which sent it a bit higher and its practically impossible to clear or flush it out!! if the rad is cold at the bottom after a run then its blocked.