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Red top engine saga continues....
chrsgrain - 1/3/08 at 06:48 PM

Well,

Been away for a week - and got a compression tester on the way back.... Not good! 60psi in all pots.

Any ideas at all? I read the bit here about the oil pressure relief valve.. sounds like a good (and least expensive!) idea... should I just take it out and clean it, or remove it all together? (Just long enough to prove that its the problem?)

Then if it isn't I guess I need to take the head off.... it was a bit low on coolant, don't suppose I could have overheated and twisted the head or something?

Chris

Dingz - 1/3/08 at 07:16 PM

You could try squirting a small amount of oil in the cylinders then doing the test again, if it makes a big difference it points to the bores/rings being the problem, if not especially as they are all the same pressure looks like the valves aren't doing their job.

the_fbi - 1/3/08 at 08:25 PM

quote:
Originally posted by chrsgrain
Well,

Been away for a week - and got a compression tester on the way back.... Not good! 60psi in all pots.

You had all the plugs out and the throttle fully open when turning it over for the compression test?

If the engines not been run for a while, till you get some oil pressure built up you will get a low compression as the may have drained their oil.

It'll take a full warmup cycle to get them fully pumped again. Generally on XE's this is solved by a tow start to get the engine running.

There should be at least 3 earths to the fuel rail/inlet, although them not being there wouldn't give you low compression.

Mr Whippy - 1/3/08 at 10:10 PM

60psi that pathetic it's suppose to be 150 - 200psi according to my gauge, is the throttle plate even opening? If all cylinders are at the same pressure it can't be anything to do with the head gasket, broken ring, holed piston or valve train as the cylinders would read different pressures. It's either blocked the exhaust some where or can't get the air in so undo the manifolds a tad and try the pressure test again.



[Edited on 1/3/08 by Mr Whippy]

MkIndy7 - 1/3/08 at 10:44 PM

I know you can't exactly do it when the engine won't run... but isin't the engine supposed to be warm when doing a compression test.

Can you turn the engine over with the cam covers off? just to watch and check whats happening under there.

chrsgrain - 1/3/08 at 10:47 PM

Ah.....

Never done one before... didn't RTFI... did the test with the throttle shut! DOH! Thanks guys, will try again tomorrow...

Chris

gazza285 - 1/3/08 at 11:12 PM

quote:
Originally posted by Mr Whippy
it can't be anything to do with the head gasket, broken ring, holed piston or valve train



Apart from having no oil pressure means that the hydrolic cam followers don't pump up fully?

Chippy - 1/3/08 at 11:16 PM

Throttle open shouldn't make a hell of a lot of difference, as the compression stroke happens with all valves shut. I think that if the "adding oil" doesn't give a much improved pressure then your looking at "maybe" having pinched the rings in to there grooves, due to the overheating, "or" your cam belt has slipped and you have dinged the valves, but it's unlikely that you would have bent a valve in each cylinder, so maybe not. Happy little soul aren't I. Ray

the_fbi - 1/3/08 at 11:25 PM

quote:
Originally posted by Chippy
Throttle open shouldn't make a hell of a lot of difference, as the compression stroke happens with all valves shut. I think that if the "adding oil" doesn't give a much improved pressure then your looking at "maybe" having pinched the rings in to there grooves, due to the overheating, "or" your cam belt has slipped and you have dinged the valves, but it's unlikely that you would have bent a valve in each cylinder, so maybe not. Happy little soul aren't I. Ray

a) If the valves aren't opening the engine can't suck any air in, so no air to compress, hence poor compression figure.

b) He's checked the cam timing and its OK.

Chippy - 1/3/08 at 11:59 PM

Air enters the engine, even on tick over, (throttle closed), or are you saying that the engines has no compression at tick over, Hmmm! think not. Ray

Ah! just re-read your post, your refering to the inlet and exhaust valves, not the throttle. Has it been established that the valves are not opening as they should, or have we not yet taken the valve covers of, if not would suggest that was done asap. Ray

[Edited on 2-3-08 by Chippy]

Mr Whippy - 2/3/08 at 12:41 AM

quote:
Originally posted by gazza285
quote:
Originally posted by Mr Whippy
it can't be anything to do with the head gasket, broken ring, holed piston or valve train



Apart from having no oil pressure means that the hydrolic cam followers don't pump up fully?



The difference they make between pressurised and not is very small, that's the tapping noise you'll hear on modern engines when left a while. Remember your engine only gets any pressure once it's started, this ones not even doing that. I've tested engines cold and most will get well over 100psi even without oil down the bores. It makes sense to test it with both manifolds pulled back before going as far as removing the head. To me if the cams are turning and the gaskets alright then it must be able to get a higher pressure.