Urgent Challenge: Should I Remove the Head?

ChevyC60
Tue, 01 Mar 2011 21:55:04 +0000
Maintenance/Repairs

Im trying to determine the cause of my engine failure and why Im only getting almost exactly 30psi’s compression on EVERY cylinder:

GM 151 2.5L (Vin-R) 4-Cyl.Engine

90,000 Miles on New Eng., Reg.Oil Chgs.

1. CYL. 1-2-3-4 (apx. 30 psi’s ±5psi) Normal is at least 105 psi’s

2. OIL - Clean

3. Water - Clean

4. Timing - Correct (Checked TDC on Cyl#1)

5. Rocker arms moving on all cylinders

6. Valve Cover removed inspected lifters all in good cond.

7. Oil drained through fine mesh and no significant metal particles found (1/10th gram).

8. Oil Pressure at time was unknown, no oil gauge or warning light displayed at time of failure.

Recent Background: Vehicle had overheated hours earlier due to known slow-external leak in cooling system. Outside temperature at time was apx. 25 deg. (F)Replaced coolant with water until permanent repairs could be made to leak. Vehicle driven afterwards with no further problems for a couple short trips (10 miles). I have limited tools and money and will have to buy tools/gaskets if I take the cylinder head off for inspection. I have over 25 years working on cars, rebuilding engines, but based on the “EVEN” low-compression on ALL cylinders and other mentioned facts, Im stumped on this one.

A. If by chance I lost a cylinder bearing (exposing an oil port) could that in any conceivable way account for precisely the same cylinder pressure?

B. Is it possible, even likely, that I could bust a head gasket ONLY in the spots adjoining the four cylinders and not in any water/oil ports (it would have to be TWO separate adjoining spots)?

C. Is it more likely, over all other improbabilities, that my newly purchased Harbor Freight compression tester is a “cheap piece of junk” and giving me false readings, explaining why I get even pressure on all cylinders?

D. In spite of the adverse cost to me, should I still take off and inspect the cylinder head, or is it the problem likely elsewhere?

I have to get on this while the weather is good for a limited time, so I have to make decisions on courses of action ASAP. Thanks in advance for your replies.

20 posts - 10 participants