Pretty sure my heads are lifting, as when on boost top and bottom hose pressurise quite bad, and then the pressure disappears when the boost goes. The engines coming out soon to be overhauled because of this but I've got a couple of questions.

Firstly are the heads lifting due to the head bolts stretching/coming loose or are the heads warping? And secondly will I need to get the heads skimmed? And if so what's the tolerance for still using standard head gaskets?

It's a classic turbo uk 2000 completely standard btw

Cheers laurence

 

Or is it just leaking head gaskets letting exhaust gasses into the system? Highly unlikely for a standard car to be lifting the heads with boost

 

The only reason I think the heads are lifting is that the pressure goes straight away when the boost goes, so surly if the head gaskets were leaking the pressure would stay there?

 

No, think about it. When you've got your foot down the engine works harder pushing out more gasses. Then when you knock it off it stops producing them.

 

Is the car loosing water?

 

I doubt very much a standard 2.0L with standard boost pressure will lift the heads.

 

Humm yeah see what you mean, just from past expeirence if theres pressure in the system due to the head gaskets it stays there and when you take the expansion tank cap of it all realeases and bubbles up which doesnt happen on mine.

No the cars not loosing any coolant, if driven really hard then a little bit will escape through the top radiator hose clamp but generally the level stays the same. I did a coolant change (the correct way) a while ago when I first found this problem but I was thinking of changing the thermostat and doing it again to see if that makes any difference. The temp level never rises above half way either and has never overheated.

What sort of boost do you have to be running to lift the heads then?

 

Get sniff test done.

 

Yeah I did that at work, it didn't show up anything. I didn't think it would as it only pressurises when on boost.

 

If exhaust gases were getting in there in any way they'd show from a sniff test. They stay in the system and coolant a fair while

 

I know I did a stiff test as soon as I found the problem so it's when there would have been most gas in there if any. All of this is telling me it's not the head gasket at fault. I even by passed the turbo from the cooling system thinking the turbo may be pressurising it but that was still the same.

 

Could there be a restriction in your cooling system somewhere - when the cars being revved the water pumps spinning faster so pumping more but its restricted somewhere so increasing pressure in the system?

 

Yeah that's not a bad shout, I've got a timing belt to do on it, so I might take the radiator out and do the timing belt and whilst there check the water pump and all the pipes.

 

For anyone whos interested finally got round to fitting the timing belt, and whilst i was there completly flushed the cooling system and put a new thermostat in and it all system to be okay with no more pressure in the system.