Gunk In Oil Filler

Mayonaisse like gunk in the oil filler cap can only mean one thing. Head Gaskets gone.

But theres no loss of power.

Someone tell me Im wrong.

Not necessarily, could be blocked breather(s).

Which breather pipes ??? I hope your right

Has your car got the plastic breather box on the right of the engine bay? (next to the right hand plenum chamber)

This can get clogged and gives exactly the same 'mayo' effect as a blown gasket. I've never experienced this myself, (mine is now bypassed by Paul Sage) but cleaning out this box should fix it.

Yep, it has that box, I'll give it a try. Thanks

Dont know the engine very well, just going on previous experience....there will no doubt be several breathers round the engine. If your cylinder head gasket is going your water also be going down by a noticable amount, you may also see vapour in the exhaust fumes.

Check you havent got a water leak problem at the oil cooler sandwich plate, or internal corrosion here..this would let water directly into the filter.

I've now got mayonaisse on the dipstip and the water in the expansion tank is still dropping.

The car still seems to run fine, although its a bit jerky on initial startup and drive off, like the coolant sensor is defective, although I changed that about a year ago.

So I guess it is the Head Gasket

Are there any checks I can do to confirm it one way or another ??

What else could it be ???

How much does any one think it will cost ???

Also, what else should I have done, while the engine is in bits ???

New liners, piston rings ???

Does anyone know how much these items are ???

Thanks in advance

Take it to a local garage and ask them to do a coolant system pressure test and a combustion gas detection test (also known as a block test I think).

I'm having these checks done to mine at the w/end, which should confirm one way or the other if the head gaskets have gone.

Theres no need to do the rings and liners unless there is a compression problem or you really feel they need doing. Its a very big job, and a wasted expense if not required.

Try www.mecaparts.com for the bits though.

Thanks guys, one last question.

My mate has a compression tester, so im going to check it myself.

Trouble is, what pressure should I get if its ok, and what should it read if its knackered

Firstly, measure the compression of each cylinder.
You may see 1 cylinder that is really low comparred to the others, perhaps it's neighbor too, so this will point to the problem area.
If it is a head gasket problem, lets hope it is only on 1 bank. So the other bank should be normal.
Unfortunately, I can not answer your specific question of what normal or correct compression readings should be.

I would guess that if it is just a problem on 1 bank, you might be better off to take both heads off and check them out together.

Let us know what you get in the way of readings.

I don't know if it's exactly the same for the GTA, so don't take this as gospel, although it might be useful as a guide! The Haynes manual for the 25 Turbo, which uses a 182bhp version of the Z7U, similar to that used in the GTA, states a minimum engine compression pressure of: 10.3 bar (150 lbf/in2)
with a maximum difference between cylinders of: 1.4 bar (2.0 lbf/in2).

Hope this is useful, but if you get different readings, perhaps it's different for the GTA.

Like I was saying, unless the engine is running really rough to suspect compression problems then there is no need to do it. Doing a compresion test wont diagnose which cylinder is causing the water pressure problem as it can be a miniscule leak.

If the engines running rough you do a leak down test. Basically each cylinder is pumped up to compression and then you listen either to the exhaust, air filter or header tank, and oil filler. If theres hissing from the exhaust then its and exhaust valve, air filter...inlet valve, header tank...water jacket or liner and oil way...oil filler. But this is only to diagnose a more serious running problem, it would have to be really chugging along.

With head gaskets and coolant pressure, you should do both at the same time and try an determine what caused the problem in the first place.