I found out about Jasper engines reading bad reviews of ATK motors. Then https://www.consumeraffairs.com/auto...smissions.html not as bad as ATK but I guess some of them are probably good. One guy on Jeep forum went threw 4 ATK motors.

 

Just find a good local machine shop and rebuild it yourself. Then you'll know what's in it. It's not at all difficult.

CarQuest does machine work.

 

Another member recommended I read this thread, and I'm glad I did.

Question for you. My '00 XJ isn't my daily driver, so I'm placing myself in the "run it as is" camp for the time being. That said, what are the "signs of head trouble" you refer to above?

Thanks.

 

The earliest signal will usually be traces of coolant in your oil that can only be detected by a used oil analysis. The best thing you can do for an early warning is to send samples of your oil off to a lab like Blackstone at each oil change:

https://www.blackstone-labs.com/

The analysis costs $28, and they'll send you the sample collection kits for free. I send off an oil sample at every oil change for all my vehicles. Not only will it detect coolant in the oil before it can do any serious bearing damage, it also gives you information about how your engine is wearing. I even bought one of their little pumps to make the sample collection easier. This makes it pretty simple: If the analysis comes back positive for coolant, swap the head (after making sure it's actually the head that's cracked and not the block).

Other potential signs:

Probably #1: Unexplained coolant loss from your overflow bottle - The level drops and you have to keep adding coolant, but you can't find any leaks in your cooling system because it's going into the oil and/or out through the exhaust. Sometimes, if you're not paying attention to your coolant level, your first indication is that you overheat because too much of your coolant has already leaked out.

Running rough with codes for misfires on cylinder #3 and/or #4 - This is from coolant leaking into the combustion chamber and interfering with combustion.

Loss of compression on #3 or #4, or a leak down test shows a problem on one of those cylinders

Intermittently running hot or temperature spikes for no apparent reason

Running hot when under load or at highway speed

Red mud in your radiator and overflow bottle that comes right back after a thorough flush - This is not "rust" as many people believe, but the precipitate that is left behind when coolant boils. That crap is sticky and can destroy a water pump in as little as three months.

"Boiling" into your overflow bottle, sometimes even when your coolant temp appears normal - This is a sign of exhaust gas escaping into the coolant, and the "boiling" may actually be the gas bubbling out. You can test for the presence of exhaust gases in your cooling system using a combustion leak tester, which you can usually borrow from Auto Zone. You can sometimes see exhaust gases bubbling up in the radiator if you run the motor with the radiator cap off and watch.

Sometimes you can actually see the crack itself by looking down into the oil filler hole between the #3 and #4 cylinders, or you can see coolant weeping up from the crack in that location.

If you're using cheap oil, you may see the oil turn cloudy or milky, and you may get "chocolate milk" on the underside of your oil filler cap. However, I put this toward the end because looking for milky oil is not reliable. The better detergent packages in better oils can emulsify more coolant, so they often don't turn milky. (Mine didn't.) Don't assume that just because you can't see it, it's not there. That's what the oil analysis is for.

You may also see your oil level appear to rise between oil changes, as coolant increases the volume of liquid in your oil pan. By this time you've probably already done some bearing damage.

Finally, if you start getting low oil pressure at hot idle, and you verify it with a mechanical gauge to rule out a bad sender, you've most likely wiped your cam bearings. Time for rebuild or replacement.

Keep in mind you won't necessarily see all of these symptoms, but if I got any one of them on a 2000 or 2001 with the original head, I'd be testing for the crack before doing anything else.

 

X2

 

Excellent information. Thanks very much for your time. I posted the following earlier today in another thread, but it may be more applicable here. I don't see this exact issue in the list of red flags you provided, so I'd like to get your thoughts if you don't mind.

My dad (who's fairly competent in diagnosing mechanical issues) came over today to check out the XJ. I let him listen to it run for a few minutes, because I've noticed a slight, but consistent, abnormal sound in the motor. He seems to think a rocker arm, or something in that vicinity, might be sticking a little bit.

Now, I have absolutely nothing to base this on except paranoia and '00-'01 horror stories, but if he's right, is this an indication of the dreaded 0331 cracking issue? If I haven't done a very good job of explaining this, let me know and I'll provide as much additional information as I can.

 

These 4.0's are known for some normal valve train noise. Some noisier than others. Perfectly normal. I guess your still planning on a valve cover gasket replacement? Until then remove the oil filler cap and take a look inside with a flashlight for any sludge build up. As far as the 0331 issue just follow Extrashakey's advice in his post.

 

Phew. You've really kept my nerves in check over the last 48 hours, EARL. Thanks a million.

 

Hey. Been there before and was doing again it until last evening. Thought I was going to have to replace my front axle assembly because of a bent axle tube. But I located a GOOD alignment/repair shop who said it's good to go. Just one bent and one trashed bracket. So I dodged the bullet.

Next time you change your oil add 1qt of Marvel Mystery Oil in place of 1qt of motor oil. ONLY additive to use. It's a engine top end (valve train + lifters) lube and cleaner.

 

Glad things worked out for you. I hear axles are kind of important. And to answer your previous question, yes, I'm still going to install a new valve cover gasket.

Good to know. I've never really used any motor/fuel additives, due to lack of knowledge.

 

MMO is one of the few respected additives around here. Stuffs been around since the early 1920's. I use it every six months in my fuel system to keep the fuel system clean. I know gas has cleaning additives but a habit is hard to break. Plus it smells good.

 

I was browsing Clearwater's site and noticed that they have new and "reconditioned" 0331 heads. Not that I'm swapping any time soon (hope not, anyway), but just out of curiosity, is a reconditioned head an okay way to go, or do you always want to go brand new?

 

Can't see anything wrong with a reconditioned one if it's got a warranty. The problem with the 0331 is the casting itself. Well the casting material as I understand it. I remembered seeing this update recently:
https://www.cherokeeforum.com/f2/her...1-head-229267/

 

I'm not sure I follow. Even if you get an 0331 from an aftermarket company, it'll still suffer from the same issue? I thought it was just the OEM casting?

 

Sorry. My post should have read "The problem with the XJ 0331.............."

There is another 0331 head called an "0331 TUPY" that was used in later model Jeeps. Not sure which ones but they were post XJ. These are the cure for the older 0331 problem heads. They're what Clearwater uses for their reconditioned heads. If you know where to look on the newer head you'll see TUPY in the casting.

There are a lot of people who have posted here saying their 2000-01 4.0 XJ's have given them no head problems at all. Do they crack? Yep. But from what I've read here not all them have.