signs of cylinder head warpage?

[ddiego]

Hello!

I've had a bit of a nightmare the last month dealing with the dealership and some issues with my 04 liberty. After they gave me a shopping list of things that needed to be done they told me the right cylinder head had to be replaced, which is going to run me for about $2400 CAD. Now to my understanding a compression test was not done and the engine obviously wasn't taken off/opened.

The bg story. it appears that my fan stopped working when I was in the middle of nowhere which overheated the engine. I stopped the car immediately when I noticed and turned it off, the oil light came on right before I turned the car off. After it was repaired, they told me there was a code to change the o2 sensor. I noticed the engine misfiring and a burnt smell coming from my ac vents. so i brought it back and they told me an engine code for cylinder 4 misfiring was showing. The spark plugs probably need to be changed as i've never changed them since I bought the car. After they inspected it again that's when they told me the head was warped, but im just curious as to how they could check that as everywhere ive looked it seems you cant determine that unless you open it up? Some wisdom would be really appreciated. Thanks!

 

[tjkj2002]

The 3.7 in the KJ is known for warping the aluminum heads when overheated or dropping a valve seat and it's almost always bank 2(passenger side for left hand drive),could be the source of the #4 misfire also.

 

[ddiego]

The 3.7 in the KJ is known for warping the aluminum heads when overheated or dropping a valve seat and it's almost always bank 2(passenger side for left hand drive),could be the source of the #4 misfire also.

thank you for the prompt reply. so probably nothing to do with the o2 sensor and the spark plugs?

 

[Conundrum2006]

Misfires can be bad spark plugs, coils, fuel injectors. Those are the easiest to try to fix.
Then valves and overall cylinder compression, below a certain point there is not enough compression to ignite the fuel.

If it were me I'd try to replace the motor, trying to piece it together by fixing a bad head gasket will only last so long before something like bearings fail.

The oil pressure warning coming on as it over heats sounds ominous.


Edit: forgot oxygen sensor can cause misfires just because they control how lean or rich the fuel mixture runs.


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[Conundrum2006]

Reading over it again. I'd probably try a compression test on that cylinder or possibly scoping it with a tiny camera.

People here know this engine pretty well I wouldn't dismiss the valve dropping as a source of the misfire, could be simple solution but after overheating it probably wont be.

Not sure if the dealer was diagnosing head gasket failure or if there was visible signs not sure what those would be. Also a blown headgasket will case the engine to miss too, either radiator fluid filling the cylinder or the lack of compression.

There's a lot you can DIY to diagnose the trouble.


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[HoosierJeeper]

I'm guessing the oil pressure light came on because of how hot the oil must have become and "thinned" out. Not good.

 

[turblediesel]

Take it to a different shop and have a compression check done while new plugs are being put in.

The burnt smell might just be solvents that were used to loosen the O2 sensor cooking off.

Head warpage is usually checked with a good straight-edge with the head off the engine. Compression check is the best way to see what's happening without major disassembly.