Christopher S

Hi! I have a 2000 limited that I strongly belive has a blown head gasket. I have oily bubbles in the cooler cap and moisty windows when heater is on. It also seems to build up pretty high preassure in the cooling system. I looked under the heat shield at the cylinder head and found the well known "0331" marking. Im going to lift the cylinder head in the next few weeks and have it tested for leakage. What are the chances that the head is NOT cracked? Hit me with your thoughts.

Dave51

There are 2 types of 0331 heads.

Those that are cracked.

Those that are going to crack.

Dave51

But that's not a cracked head. That's a leaky heater core. It's easier to change the head than to change that thing.

Christopher S

Im thinking that the core leaks cause it can't handle the high preassure created from exhaust going from a cylinder via a blown gasket and in to the coolant. Could that be the case?

Dave51

So let's think about this. Are you adding antifreeze? Blowing white smoke out the back? Overheating? Bubbling in the overflow?

Seriously, IDK the percentage of cracked 0331 heads, but one small poll I read a while back was putting the number at ~20-25%.

Dave51

Maybe, but if your pressure cap is working correctly the system should never pressurize greater than 18 lbs., which shouldn't blow the heater core out. Unless it's just old and corroding out.

Is the carpet wet under there?

Dave51

IIWM I'd start by pulling the spark plugs. A cylinder burning antifreeze will be sparkly clean. An 0331 crack is usually between cylinders 3 and 4.

Dave51

Most important is the oil milky? If so, shut down immediately, if you haven't done so already.

Christopher S

My jeep White smoke, No wet floors. It rises kind of high in temp when ideling for a Long while but my electric fan does'nt start as supposed. I can see traces of coolant spraying out of the cap and the upper radiator hose is really hard. The most suspect thing is the bubbly oily content in the cooler cap. It looks almost like the top of the coffee filter when you just made your morning coffee. I tried to perform a comp test but it's hard to do because the treads in my spark plug adapter is to short to get a grip in the head. I will try to do it again just pressing the gauge with a rubbet seal. Sorry if my english is hard to understand...im from Sweden 🙂
​​​​​​living in Sweden makes it a bit hard to find a cylinder head. If I would have a Volvo there would be tons of parts in every barn but jeep parts a bit more rare 😄

Christopher S

Sorry I just saw a mistake in my reply. My car does not white smoke.

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Christopher S

I think I will try to comp test again. After that i will lift the valve cover and have a look. I've heard about the between cylinder 3 and 4 issue and I think I saw a video on YouTube where the crack in the head was visible om the top of the head under the valve cover. Is that common to see cracked from above?

Dave51

Ja.

Christopher S

Ja!?

Your swedish is better than my english! 👍🙂
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Dave51

Over here you can borrow a cooling system pressure testing kit from AutoZone for free. Don't look like you got AutoZone over there tho. Check around your parts stores if they have free loaners. Pressurizing the cooling system may be a better diagnosing tool than checking compression.

Is there bubbling in the overflow? Is the radiator cap in good condition? If you run the engine with the cap off is there bubbling?

Hoping for the best!

Christopher S

I have'nt seen bubbles in overflow. I have another cap from the old radiator that I can try. If I remember correct there was a few bubbles when running with cap off. Will have a look tomorrow or this weekend. It's time for vikings to have a good nights sleep now but I will post when I have checkers everything.
Big thanks for your help so far.