Hi,

I have an 87 trooper with the 4ZD1 2.3l gas engine in it. About 2 1/2 years ago it broke down with a leaking head gasket and a cracked cylinder head. I believe the head cracked when I had a "freeze plug" pop out on the freeway. I got a "freeze plug" from the dealer and installed it in the trooper. It ran ok for a couple of months and then it died.

I got a used cylinder head and had it pressure tested and it tested good but it needed a valve job. I had the shop that tested the head to do the valve work. They also milled the head (as needed) for me. The head sat for about 6 months all wraped up in plastic on the kitchen floor.

About a year ago I went to install the cylinder head in the trooper. I got a new factory head gasket and and installed the cylinder head in the truck.

When I installed the head in the truck I went to check the compression and I got some poor readings. The first time I got the following readings.

Cyl Reading

1 30 PSI
2 30 psi
3 120 psi
4 50 psi


After I got these readings I took the cylinder head bolts out one at a time. Then I got a tap and chased out the cylinder head bolt threads in the block. I then installed new factory cylinder head bolts. I torqued the head bolts to 72 ft-lbs and went to check the compression again. These are the compression numbers I got the second time.


cyl reading

1 50 psi
2 50 psi
3 150 psi
4 70 psi

I have checked the "mechanical" timing several times to make sure it was correct. Everything lines up and the timing belt is tight. I have checked the valves to make sure that they were set correctly.

I am hearing a popping noise when I turn the engine over to check the compression in the engine. The noise is in rhythm with the turning of the engine. The noise is only present when I have the compression gauge screwed into a cylinder to check the compression. When I am not checking the compression the engine turns over just fine with just the regular engine spinning noise.

I am at a loss as to where to go from here. I changed out the cylinder head on my parents 90 trooper about 3 years ago and when I put it back together the compression was fine. I want to get this trooper back together and running.

I am stuck right now. I can't continue with the repair with compression numbers like the ones I am getting and I don't know what is causing the problem. The trooper ran good for 2 years when I first got it. I even got it pass the state emissions test.

I'm sorry for the long post. I am open for any ideas into what is causing this problem.


Thanks,

Mike