Jake Johnson

Hey guys, so I have had a repeating misfire code problem with my 2001 XJ Classic, and I have just recently noticed that my engine coolant in the reservoir is blackened with oil. I've been told that I may have a cracked head, because when I drive, eventually odorous smoke comes out the front of the car without the temperature gauge ever going above the halfway line. I need to flush the coolant reservoir and replace it, but I'm not sure if I should go ahead and try to see about the cracked head before it gets un-drivable, or if I should pray it never breaks. It's got 187k miles on the original engine and it's been kept in really good shape its whole life. Please help, I love my XJ and I don't know what to do as the only "mechanic" experience I have is changing a headlight.

EZEARL

WELCOME to CF.

I haven't dealt hands on with the 0331(cracked head)issue but those who have will reply I'm sure. First thing is to stop running the engine until you verify if it's cracked or not. Here's an in depth thread that will help you understand what your dealing with.
https://www.cherokeeforum.com/f2/00-...erview-118922/

extrashaky

If the head is cracked, it's already broken and needs to be replaced. Replacing the head is a one day job. Most people get it done in an afternoon.

If you wait, coolant in the oil will destroy the cam bearings, your oil pressure will drop to zero, and you'll end up needing an engine swap instead. That's not a one day job and is considerably more expensive than a head swap.

Even though it might be running okay now, if there's coolant in the oil, it is doing damage to the bearings. Every minute you run the engine is a little more wear. It's not a matter of praying it never breaks. It's a matter of stopping the ongoing damage before you lose the engine altogether.

But the upside is that if you replace the head in time, the bottom end will be fine, and your Jeep can still run reliably for tens or hundreds of thousands of miles to come.

Kymasabe

Oil in your coolant is a bad sign, you dont have to wait for something to break, it already has. If it were an earlier year, I'd suspect a failed head gasket, but a 2000/2001 will more likely be a cracked head. Check your oil, make sure you're not getting coolant in the oil, if you are, stop driving it immediately before you destroy the bottom end. And, many members here have had good results with Clearwater cylinder heads if you need a head. Good luck.

extrashaky

A couple of notes on that:

First, if you really have oil in your coolant, it's highly likely you also have coolant in your oil. Oil and coolant are not supposed to ever contact each other in the motor. If they do, it's probable the contamination is going both directions.

Second, you can't always tell you have coolant in your oil by looking at it, smelling it, touching it or tasting it. The detergent packages in modern oils have gotten so good that they bond moisture well enough that the oil itself doesn't turn milky, and it may not change color at all. Mine never showed a milky appearance even when the oil level rose between oil changes. The only way to rule out coolant in the oil is to send a used oil sample to a lab like Blackstone (link: https://www.blackstone-labs.com/ ). They'll send you the test kit for free, and the test itself costs $28.

Again, don't wait on this. You have an opportunity to save your engine, so take it.