So where to begin - engine questions

[Rockfrog]

So sold my 92 HO motor, and just got it back, again.

So it's going back to going in the MJ.

So, it has zero compression on 3 and 4, low on 2, and 5, good on 1 and 6.

Pulled the head and found wet gasket and coolant in 3/4.

Other wise it looks better than my 88 4.0, can even see some cross hatching in the cylinders. Pistons are tight in the bore, head looks good, can't see any visible issues really. My thoughts are a bad head gasket (either install or blew it at some point).

Any advice on where to look for a reason for the low Comp? It did sit for over two years, stuck rings? When I started it up before chopping and stripping it started and idled great.

[Akula69]

There are more then a few reasons why coolant can enter the into the bore(s), and the culprit is (usually) the head gasket, but could be any of the following:

 

1) Crack in cylinder/water jacket (which would 'force' the head gasket due to incompressibility of coolant)

2) Too much compression or Detonation (perhaps caused by EGR failure - but 92 doesn't have EGR?)

3) Improper re-assembly (oops!)

4) Overheating

5) Cracked head and/or other head issues.

 

Do you know what the person(s) you sold it to did to the motor...did they abuse it? Sitting for two years and then starting up (without a couple of turns on the oil pump through the distributor hole or at least a squirt of oil though the spark plug hole) can cause the rings to stick. Did you try and turn the engine over with a wrench on the harmonic balancer before cranking it after the storage?

[Rockfrog]

The Cherokee it was in sat for two years (maybe more). The person I sold it to just replaced the rear main and come tested it. Was a friend of mine, so he got his money back and I got my motor back.

I'm leaning towards a popped gasket due to overheating, there were a few leaks when I brought the Cherokee home. Looks like someone spent a ton of money trying to fix everything but the main problem - a leaking water Flush Tee on the heater hose. And a dead fan clutch.

I can't see any indication of cracking, and the water was getting in on the head side of the gasket.

Will have to check for warping when I get home after this shift. But from what I can tell, a new gasket and I'm good to go.

Probably just order rings and bearings and a timing set anyway before I drop it in (my 88 block NEEDs machining, the 92 doesn't)

[Akula69]

Leaking water from a 'T' fitting makes me lean towards overheating. The exhaust ports for cylinders 3 and 4 are close together on the head, and has been a source of multiple problems in the past (vapor lock on #3 injector; cracks in head, and gasket failures) even without an overheat condition. I would suggest getting the head checked for warp and try a new gasket and then check your compression.

[mjeff87]

 The exhaust ports for cylinders 3 and 4 are close together on the head, and has been a source of multiple problems in the past

 

 

X2......this was the 2.5L in my TJ when the head gasket went (the first time, LOL).  Between #2 and #3 (same as 3-4 on a 4.0).  Coincidentally, the one head bolt on the intake side of the block right there was CEMENTED into place due to high heat.  I had an exhaust manifold crack on the inside right next to the block that I never knew about.

 

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