Blown Head gasket or cracked cylinder head?

[archimedes]

Hi Everyone. I have a 2005 Jeep 3.7 Grand Cherokee Laredo. I'm getting a P0302 (misfire cylinder2). I took the spark plug out, and put one from a working cylinder, and a coil from another one in. After a few starts, I had the same misfire code. I tried doing a compression test, but I consistently am getting around 160 psi (I checked all of the cylinders, and ironically, that's the highest!). Now for the bad part, during this, I noticed my coolant level definitely dropped, and I definitely noticed white smoke from the exhaust). On some of the test drives, I definitely had plenty of bubbles in the coolant reservoir, but sometimes there were none. And I definitely heard rushing water any time I stopped and started moving again. Starting it up, it shakes for about 20 seconds, but then smooths out, and the idle feels perfect during a short drive. I've attached a picture of the spark plug (one is from the first time it misfired, the other is from my next attempt in the same cylinder. I thought one looked coolant fouled, and the other oil fouled).
Do you know if this sounds like a head gasket failure, cracked head, or some other problem? I had thought maybe the injector wasn't firing, but I don't think the plug looks like that (though I'm not an expert at reading the plugs), plus the coolant issues (which I hoped would be unrelated, but think they are). Thanks for any thoughts!

 

[cptbarkey]

Either or, your symptoms could be the same result. Your symptoms seem pretty in line with some kind of possible cylinder head failure.
Is there oil mixing with coolant? Is there coolant mixing with oil?
Have you tested the thermostat?
Does your water pump still function? Does it still have fins?
Part of a head gasket repair standard procedure is to have the machine shop inspect the head for cracks.

 

[slacktide_bitog]

You could try using head gasket sealer to see if the problem goes away. A relatively cheap way to start

 

[archimedes]

Thanks! The water pump was replaced a year ago, so although I haven't inspected it, it should be ok. I haven't tested the thermostat (though I did have a block in the heater core a few months ago, and the thermostat was on the to do list, though it was believed to still be working). In the radiator, there might be a slight indication of oil in the coolant (but I'm not positive).
Thanks for the suggestion, I'm little worried about trying the sealer. I have read the success stories on using it and haven't ruled it out, I'm just a little more inclined to replace the broken part if I can figure it out (I'm not worried about taking the engine apart, I'm more worried about not finding the problem).
I was hoping that the symptoms would indicate things one way or the other.
For the machine shop, do you pretty much say, check it for any cracks? Last time I had a failed head gasket, I had no idea what I was doing, and just cleaned everything up and put it back together...it lasted 60K miles before I switched cars...this time, I don't want to guess and possibly have to do the job twice.

 

[K-Man]

If you replaced the water pump after the engine overheated, some damage to either the head gasket or a head was done then and is now getting worse. For some engines, don't know about the Chrysler 3.7, any overheating will crack a head.

One thing to be concerned about is a cracked engine block, not just a head.

 

[Hirev]

For around $100 bucks on amazon you can get an articulation borescope .33 inch camera with a light.. You can see what is going on.

 

[eljefino]

The cylinder should be steam cleaned if it's burning coolant. Neither of those plugs look steam cleaned. The one on the right looks substantially worn.

The sloshing water indicates you're low on coolant right now, you don't write that you've topped it off.

Exhaust in the coolant is a pretty sure sign of head gasket issues, unless you're burping air from being low on coolant.

Mixed info here in the diagnosis.

 

[archimedes]

Thank you. A lot of helpful info to write back to. When the water pump went (about 15K miles ago), the temperature gauge did not indicate overheating, but that was a concern with a crack, thanks.
I like the borescope idea.
eljefino-The plug on the left was in the engine when it first misfired. That plug has about 40K miles. The one on the right looked like that after 3 miles..it came with the car so it was used, but looked clean (I saved the original incase something like this happened). I thought they looked like they were ash fouled, but I'm not experienced to know what they show. The left had white-ish scale like deposits which I thought might be coolant, the right was more black deposits which I thought meant oil. I hadn't topped it off, so the level was low when the misfire happened, but I do know the level had been holding steady prior to this, and just suddenly dropped (I check it once a month after the water pump replacement, and just a few days before this happened, it was fine, the level has remained steady...so it definitely dropped). I'll take a look with topping it off to see if the noise goes away.

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[zzyzzx]

For the machine shop, do you pretty much say, check it for any cracks?

Yes. I'm pretty sure they will know what to do if you ask them to check for cracks (which, I think is pressure testing).