18 replies to this topic

[alanc16]

piston 1 - 50psi
piston 2 - 35 psi
piston 3 - 35psi
piston 4 - 35 psi :

could this be something other than a head gasket?

[Danny87]

According to those results it seems the compression is certainly down on three out of the four cylinders. That's quite a big difference too, two or three PSI isn't much of a problem but we're talking 15 PSI. I'd personally find it hard to just call that normal considering the engine has 100k on the clock, mine does too but I'd be confident of results being more similar over each of the four cylinders than in your case.

Unfortunately the only way of further fault finding would be to remove the cylinder head and check the interior condition of the cylinders and cylinder head. Those results could suggest the timing belt has snapped and resulted in valve to piston damage - but you are sure the camshafts are turning and the belt hasn't gone?

Another possibility is that the headgasket has gone between cylinders resulting in a loss of compression, bear in mind you don't always need 'sludge' in your oil for the headgasket to have failed.

A lot of this is just possibilities and it seems the only sure way of knowing is to remove the cylinder head. You've checked there's fuel, you've checked for a spark and there doesn't seem to be many more options to check sadly....

Hope that's of some help

[Stoney871]

I agree, it's either a head gasket failure or because the pressure has dropped in 3 of 4 cylinders it could well be a warped head.
As stated before i'd spin the head off and check the gasket first then check the head for warping - even a very tiny difference can cause a lot of problem.
If that looks ok get a valve leak test done.
Anyway once the head is off something may become instantly obvious.

1. Lack of oil causing the rings to be overworked. 2. Old (worn) and weak rings. 3. Crack or opening in the head - but that doesn't necessarily mean water in the oil or oil in the water. 4. Cracked cylinder 5. Burned, warped or cracked valve(s). 6. Burned or cracked piston. 7. Cylinder worn or out of round. 8. Blown or leaky head gasket. 9. Sticky valve(s). 10. Broken or worn valve spring(s). 11. Bent/worn pushrod(s) 12. Worn camshaft, or a broken lobe on the cam. 13. Worn or bent rocker arm(s). 14. Collapsed lifter(s).

it could mean several things from damaged rings and cylinder walls to tiny cracks in the piston heads or even a sticking or weak overhead valve if they have them

Low compression either from valves or rings. You can do the test wet and dry. Check the lbs. dry and then give a little shot of oil in the plug hole and check the lbs. If the pressure goes up wet, then the rings are losing the pressure. If the pressure is the same wet or dry, then it's a good chance that it needs a valve job.
This may be caused by burnt valves,worn piston rings,blown head gasket

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[mondeomaster1982]

Before you tear the engine to pieces. Can you decribe any sounds or knocks from the engine. Tell us exactly what happened when you said you booted it from a set of lights etc. what rpm etc

Could be crank position sensor or anything like that sometimes these can go wrong without showing up on diagnostic tools.

I know you said you dont want could be solutions but it would help if you detailed exactly what happened when it died.