Overheating

[Chrishoughton1989]

Hello all. Car has started overheating if driven hard for a few miles. Any ideas. Tryed bleeding rad several times. Water is being pushed into expansion tank and boils over.

Thanks.

[1990timeismoney]

Have you checked the thermostat

[Chrishoughton1989]

No haven't checked that but on start up its a bit rough like water is getting into cylinder. All pipes get hot too does that mean thermostat ok ?

[1990timeismoney]

Im not completely sure.my car had a overheating issue when i got it and that was due to thermostat.there's alot of knowledgeable people that will be able to give you more information.

You could always take it out and test it make sure it is ok.

[AdamB]

Check the thermostat first. But pushing water into the overflow isn't a good sign. So I would get a compression/leak down test done as well to be safe.

[Chrishoughton1989]

Yes will do. Just doesnt overheat until you have slowed down. It's fine when going fast for miles and as soon as you go slow it goes in the red.

[Chrishoughton1989]

Any ideas.

[StuDoc 72]

Smell the coolant to see if it smells of petrol.

If it does then something is up most likely the gasket or block.

This is why I traded in my VXR basically when you are driving the car on the compression stroke it forces pressure into the water system causing an air lock which builds and build the coolant has no where to go untill it reaches the spring rate of pressure on your rad cap which opens and lets it move into the overflow tank.

Hope this helps buddy but the big give away will be the smell of the coolant.

[Chrishoughton1989]

Thank you. Yes coolant smells of fuel. Its looking like Head gasket more and more. Job for the weekend. Lol

[StuDoc 72]

Defo the h8ead gasket at the very least then im afraid buddy. Not even any point in continuing your diagnosis untill you have stripped it and just hope its the gasket thats fucked and not worse.

[AdamB]

Yes will do. Just doesnt overheat until you have slowed down. It's fine when going fast for miles and as soon as you go slow it goes in the red.

Is the fan cutting in?

[Chrishoughton1989]

Yes the fan cuts in. Cheers

[StuDoc 72]

The reason it doesnt overheat when going fast is the heat generated keeps the thermostat open Along with the high engine revs. The coolant is rushing around the system with alot of speed and force which in turn prevents an airlock and basically bleeds the air into the overflow.

As soon as you slow down things begin to cool and an airlock can be formed. If you allow the car to heat up and then try to remove to pressure cap the coolant will most likely have alot of pressure and all gush out. This will confirm what ive already said.

[Chrishoughton1989]

Thanks for everyone's help. Will order head gasket and bolts today. Anything else while doing it ? Thanks.

[StuDoc 72]

You want to strip it down before ordering buddy. It may be the block or somthing else and a gasket will do nothing.

Best off replacing the thermostat and water pump. Possibly the timing belt if needed and the valve seals may be worth doing while the head is off.

[Chrishoughton1989]

Ok thanks. Just had it running for half hour and can see stream coming from back of radiator. Would a Leak cause this. But coolnt still smells of fuel. Thanks.

[StuDoc 72]

A leak is unlikely to cause it to overheat you could say it would because it prevents the system being pressurised but unless its running low then I imagine it would be ok. the pressure only stops the water boiling it doesnt prevent the engine over heating. So I would say no it wouldnt cause that.

If it smells strongly of fuel then that almost certainly indicates the problem. Fuel can only come from the inlet mani/ cylinders and if you have over heating aswell it looks like cylinders.

Strip it down im afraid mate.

[Chrishoughton1989]

Thanks again. Coolent was getting low fast. But like u said fuel shouldn't be in coolent.