Low-no compression 5.2L jeep

4x4fever

4x4fever

New Member
Joined
Jul 5, 2005
Location
abingdon,va
How do I diagnose this? #2 and #8 cylinder have low compression. Stumbles at stop signs and getting worse. Its a GC with the 5.2 and 180k on it

Burnt,stuck valves?
 
How low is the compression, also has the lower intake pan been leaking? Do a leak down test on those cylinders.
 
Its not my jeep. What a mechanic told the owner of this jeep. I have no way to do test but if I did what would it tell me?
 
A leak down test would tell you where the compression is going rings, valves, headgasket etc. it works by measuring the amount of leak in a cylinder with a known air pressure reference. I would not even try to diagnose a low compression condition with out doing a leak down test.
 
Got more info. When it stumbles and dies at stop signs its hard to start back. No info on #'s for compression test. He told me its never been hot, but he does have to periodically put antifreeze in it, although it does not leak any anti freeze.

Hmmmmmmmm
 
Let's pretend leakdown test hasn't been invented.

It is obviously burning antifreeze since its losing it and not leaking.

That would mean,headgasket, but compression is low on two cylinders (2 and 8) on same head, and usually on headgasket is opposite cylinders on each bank so that could be a cracked head?

Going to look at it saturday.
What tricks can I do to test more?

Filling the radiator to the top,starting and watching for bubbleas would be a head gasket? I could sniff the exhaust, look for wet plugs?

Doin all that and knowing its losing antifreeze, but not leaking would lean it more to headgasket or cracked head instead of a burnt valve, or worn rings? Input needed I'm just guessing and throwing out ideas
 
If your thinking head gasket or cracked head it is usually the cylinders next to each other, not at opposite ends of the head. There is a chemical test that is really easy to do if the head or head gasket is suspected though get a combustion leak checker most auto parts stores have them these days. Also the 5.2/5.9 V8's when the thermostat gasket or housing is seeping most people don't know it because it usually evaporates before they can see it, since it is buried under the alt/ac mounting bracket.
 
rob92xj said:
If your thinking head gasket or cracked head it is usually the cylinders next to each other, not at opposite ends of the head. There is a chemical test that is really easy to do if the head or head gasket is suspected though get a combustion leak checker most auto parts stores have them these days. Also the 5.2/5.9 V8's when the thermostat gasket or housing is seeping most people don't know it because it usually evaporates before they can see it, since it is buried under the alt/ac mounting bracket.
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Right on head gasket it would be either 2 and 4 or 3 and 4 if opposite banks? Really all I care is that its not the rings. I want to fix,replace heads and drive it or if its rings swap in a donor. This is a future cheap jeep for me. Seen a used engine for 250. So this one should be worth asking price. Just making sure I won't lose my ass. I wouldn't call myself a mechanic but I'm a prertty good parts changer
 
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