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Gentlemen:

I have a 1995 LWB (i.e. 4.2L), 150,000 miles, generally running well but I have a leaking head gasket; it leaks to the outside of the engine on the front left bank. There is no visible oil in the coolant or vice versa. I lose about a cup of coolant every 10 days and can visibly see where it seeps.

I’m getting ready to do the heads myself and, having sought previous advice here, plan on a new cam and lifters as well as a timing set while I’m in there.

I’ve looked down the oil filler spout with a flashlight and mirror and the area appears to have a nice medium brown patina with no obvious sludge.

I did a full compression test today, both dry and “wet”, after reading up on the procedure in the RAVE manual as well as other sources. I’ve never done this before but am satisfied that I did it correctly. However, I need help to interpret the results.

The LEFT bank has uniform dry pressures ranging from 144 psi to 150 psi and a mean average of 147.5. With a squirt of oil down the plug hole, the “wet” pressures range from 156 psi to 160 psi. The average increase in pressure from dry test to wet is about 7.7%.

All things considered, these seem to me to be acceptable numbers, albeit on the low end of the range.

But things are notably different on the RIGHT bank: The dry pressure average range is about 18% higher at 175 psi (range 165 to 180) and the “wet” average is similarly higher at 193 psi.

I would be a happy man indeed if all 8 cylinders registered like the right bank.

So…why is there such a large (18%) difference between the two banks and what is the significance in terms of engine health? Am I throwing good money after bad by redoing the top end?

My own preliminary thoughts are that the leaking head gasket on the left bank is somehow affecting the entire set of cylinders on that side. But the leak really appears to be isolated to the outside of the #1 cylinder area. I also wonder if the head might be warped but then I would expect to find more evidence of leakage elsewhere. If it was a case of a few poorly-fitting valves, then I would expect to find one or two cylinders out of spec but things are uniform here.

How can such a uniform and consistent difference between the banks be explained?

Sorry for the long post but I know that there are some sharp mechanics out there and I have become a little obsessed with this project.

Cheers,
Bob
 

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My initial thought is that the right hand side head has been off the car and has had some work that the left hasn't - valves reground, new valve stem oil seals perhaps?

I'm not sure what the history of the car is, but I guess it's possible that a previous owner lost the head gasket on the right and just pulled and overhauled that head.
 
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