extrashaky

When my head went, I was having minor cooling issues and red mud as a result. Not knowing what it was, I overhauled the cooling system and flushed the hell out of it. Three months later that crud was back, because I hadn't corrected the source of the problem. No amount of TLC to the cooling system would have helped that.

Notice in OP's story above that the prior owner had recently flushed the cooling system repeatedly and had done some other cooling work on it. To me, that's a huge red flag that the 0331 is cracked, but the PO didn't know what to do about it and so was trying bandaid fixes until he finally decided to get it looking good just long enough to unload the problem onto someone else. Over and over there have been posts just like this, where the thing had recently been serviced and looked great, but after a few weeks or a month the 0331 head crack reared its ugly head.

OP, do the combustion leak test. You might also want to check your compression, which is easy and free if you borrow the kit from Auto Zone. A leak down test wouldn't be a bad idea if you have an air compressor. And if it were mine, I'd send off an oil sample to Blackstone.

You may not have a cracked head. I hope you don't. But you have a lot of the red flags associated with it.

Tbone289

Yeah, like I said before I think that's good advice considering this is a 2000. Just looking at it and seeing red mud doesn't necessarily mean a cracked head, but the combustion leak test should definitely be done. I didn't intend to minimize the importance of that.

JerpCherooke

Okay. If I just go to parts store and ask for a combustion leak tester, they'll know what I'm talking about? I saw autozone has an 'OEM Block Tester'. Is that it?

​​​​​​Does anyone have a good link explaining what a combustion leak is? Or a good explanation?
​​​​​

Correct me here when I say something stupid, but I just want to make sure I kinda understand the 0331 problem correctly' so I'm gonna dumb it down a bit:

Some (or all??) 2000 XJ engines were manufactured with some kind of faulty casting (the 0331 casting?) that left a structural weak point in the head, which is more likely to crack under high temperatures as opposed to heads with a different casting number. And the concern in my case is that the cars coolant system has been completely neglected. So this could cause the engine to overheat, which could cause the 0331 crack, and if the PO knew about it, he may have pawned it off on sucker like me?

​​​​​​... Am I on the same page as everyone else?

FWIW, in the 1500 miles I have put on it so far, I haven't seen the temp go much above 210*.

extrashaky

If you have a cracked head, cracked block or a blown head gasket it can allow coolant into the oil and/or exhaust gases into the coolant, depending on where the breach is. If you have a crack from the combustion chamber to a water jacket, the explosive pressure inside the cylinder will push hot exhaust gas through the crack into the cooling system. That hot exhaust gas boils the coolant at that spot without necessarily overheating the vehicle. When coolant boils, it precipitates out that red mud into the cooling system. Red mud isn't a guarantee you have a combustion leak, but it's a red flag that you might.

The combustion leak tester, also called a block tester, is a big fat syringe with a bottle of detector solution. You put some of the solution in the syringe, then put the syringe over the radiator filler hole and draw some of the air above the coolant into the syringe. If there are exhaust gases traveling through your cooling system, the solution in the syringe will change color.

You can buy your own kit for $50 to $60, but someone posted here a while back that they were able to borrow the kit from Auto Zone through the tool loan program. You might want to call around before going to the store to make sure they have one.

In 2000 Chrysler changed the head to the 0331 casting number (the number refers to the port design), which was changed from prior years to accommodate the difference in the ignition system. The original 0331 had a casting flaw that caused some of them to crack. Chrysler quietly moved production of the heads to the Tupy foundry in Brazil in 2002 (after the XJs were out of production) for use on 4.0L motors in other Jeeps. The Tupy 0331 heads are made from a different alloy with a higher nickel content to prevent the crack, so it's not clear whether it was a design issue or a materials issue.

ALL 2000 and 2001 XJs left the factory with the crack-prone 0331, although at this point many of them have been swapped out by their owners. You don't have to neglect or abuse the cooling system to have the head crack, nor does it have to be overheated. Many of them just crack on their own. Many others go 300K miles or more. You really can't predict it, although overheating one does significantly raise the likelihood of a crack.

If you do have a cracked head, you can't necessarily blame the prior owner for it. He may have neglected the cooling system, or the cooling system issues may have been caused by the head crack. You can't be sure what caused what.

As for his motivations when selling, we can't know that. He might have felt the vehicle was becoming unreliable with some cooling issues and decided it was time to get out from under that, so he did what anyone would do and freshened the vehicle up to make it as attractive as possible to potential buyers. Or he might have suspected a problem and was trying to hide it. If he told you about the earlier flushes, he probably wasn't trying to pull one over on you.

And again, you may not have a cracked head, and I don't want to scare you. You just have some of the red flags that make it worth ruling out before firing the parts cannon at the cooling system. Besides, even if it's not a crack, you do need to know about the potential problem if you're going to own a 2000 or 2001 XJ so that you know what to look for and can catch it early if it happens. If you catch it early, it's $500 or so and a weekend swapping the head to remedy it. If you let the head crack go, you end up wiping the cam bearings and swapping or rebuilding the long block.

JerpCherooke

I did it for a couple of minutes, so what do you think?

Before
After
​​​​​​It's not quite as blue. So do you guys think there is a combustion leak?

extrashaky

Still looks blue to me, but you're the one looking at it in person. Assuming you gave it time to warm up, if you're not seeing a change to green, it's probably okay.

I would still keep an eye out for head symptoms if it were me, but at this point I would go back to the original plan of flushing the hell out of the engine. Flushing with water isn't going to be sufficient with this level of crud. Use a chemical flush like Prestone, or if you know anyone who sells Amway, you can run 1/4 cup of Amway laundry detergent through the system the same way as the Prestone flush. Don't use CLR in your cooling system, because the manufacturer says it can damage radiators and heater cores. You may need to flush and refill multiple times to get the crud out of the water jackets.

jlschneck

I purchased a 98 Cherokee Sport for my daughter's first vehicle a year ago. I knew absolutely nothing about them and the 4.0 motor prior. Needless to say I have had and/or done a considerable amount of work to get it "cleaned up" if you will.The prior owner severely neglected the transmission and cooling system. I agree with Tbone289 that your symptoms point to a similar scenario. 5 trans fluid drain and fills have been completed and the fluid is still not where I want it. First was completed by a transmission shop at purchase when they also replaced the filter. No flush, just pan drop and fill. I have since completed the 4 other drain and fills in conjunction with the oil change intervals. The last 3 drain and fills have been done consecutively with a week apart from each other in order to get the system clean. Similar situation with the cooling system. Shortly after purchase the water pump and thermostat were replaced and coolant was flushed. Not aware of the potential rust issues with the cast iron blocks I assumed all was good. I was amazed at how dirty the coolant was when I went to replace all of the hoses a week ago. Looked like someone had poured reddish orange mud into the top of my radiator filler neck. Coolant recovery tank also had about an inch of this muddy sludge at the bottom. Started researching and determined this would require multiple flushes to remove the rust. I also found a product called Thermocure by EvapoRust. Very high reviews and is designed specifically for removing rust from vehicle cooling systems. I purchased a bottle at Walmart. Can also get online if not in your local Walmart stores. One quart treats up to a 3 gallon system.Use at your own risk as I have yet to complete the entire recommended process. I drained the radiator at the petcock. Removed bottom rad hose and heater inlet hose at water pump housing and flushed heater core, radiator and engine block separately from each other with my garden hose. Once the water was as clear as I could get it I flushed with two gallons of distilled water, reattached all hoses closed the petcock, added the Thermocure and filled system with distilled water. I performed a live flush by having my daughter drive the vehicle as normal for about 4 days. I then drained the radiator at the petcock and removed the bottom rad hose. Fluid was black to dark grey. This is apparently normal as the chemicals in the product turn black as it removes the rust. I then proceeded to flush the system with tap water until the water was clear. Flushed the tap water with distilled water, closed everything up and filled the system with distilled water. Will let the daughter drive it for a few days and drain and flush again later this week. Will continue this process until the system is clean. At that point will fill with 50/50 mix of antifreeze and distilled water. I will follow up with my final results after completed.

jlschneck

I purchased a 98 Cherokee Sport for my daughter's first vehicle a year ago. I knew absolutely nothing about them and the 4.0 motor prior. Needless to say I have had and/or done a considerable amount of work to get it "cleaned up" if you will.

The prior owner severely neglected the transmission and cooling system. I agree with Tbone289 that your symptoms point to a similar scenario. 5 trans fluid drain and fills have been completed and the fluid is still not where I want it. First was completed by a transmission shop at purchase when they also replaced the filter. No flush, just pan drop and fill. I have since completed the 4 other drain and fills in conjunction with the oil change intervals. The last 3 drain and fills have been done consecutively with a week apart from each other in order to get the system clean. Similar situation with the cooling system.

Shortly after purchase the water pump and thermostat were replaced and coolant was flushed. Not aware of the potential rust issues with the cast iron blocks I assumed all was good.

I was amazed at how dirty the coolant was when I went to replace all of the hoses a week ago. Looked like someone had poured reddish orange mud into the top of my radiator filler neck. Coolant recovery tank also had about an inch of this muddy sludge at the bottom. Started researching and determined this would require multiple flushes to remove the rust. I also found a product called Thermocure by EvapoRust. Very high reviews and is designed specifically for removing rust from vehicle cooling systems. I purchased a bottle at Walmart. Can also get online if not in your local Walmart stores. One quart treats up to a 3 gallon system. Use at your own risk as I have yet to complete the entire recommended process.

I drained the radiator at the petcock. Removed bottom rad hose and heater inlet hose at water pump housing and flushed heater core, radiator and engine block separately from each other with my garden hose. Once the water was as clear as I could get it I flushed with two gallons of distilled water, reattached all hoses closed the petcock, added the Thermocure and filled system with distilled water.

I performed a live flush by having my daughter drive the vehicle as normal for about 4 days. I then drained the radiator at the petcock and removed the bottom rad hose. Fluid was black to dark grey. This is apparently normal as the chemicals in the product turn black as it removes the rust.

I then proceeded to flush the system with tap water until the water was clear. Flushed the tap water with distilled water, closed everything up and filled the system with distilled water. Will let the daughter drive it for a few days and drain and flush again later this week. Will continue this process until the system is clean. At that point will fill with 50/50 mix of antifreeze and distilled water. I will follow up with my final results after completed.

extrashaky

¶

Please?

jlschneck

Sorry....

I added new paragraphs and formatting to my replies but could not figure out why they were not being applied to the submitted post.

I believe I have figured it out? Needed to change the editor under my options.

JerpCherooke

Okay, so I am planning on flushing the coolant system, but here is my problem. I don't have a place to work myself. I asked my brother if I could do it at his place, and he said it was fine as long as I didn't make a mess. Well I was planning on draining the radiator via the drain ****, but after reading, it sounds like this would cause more problems than it would fix. So I guess my option is the lower radiator hose. Does anyone have any recommendations on how to minimize spillage? If I mess this up, he probably won't let me use his garage again so I really would like to make this as clean and painless for him as possible.

Bugout4x4

That's the problem with working on a car in the city, it's OK to own a car but it's just not OK to work on it yourself, society insists it should go to a shop where they have proper containment and disposal. Honestly, myself, I would find another place out of town to do it where you can really hose it out good.

Man I hate the "Known by the state of California to cause..." and the EPA. OK... PROVE IT BEFORE YOU SPREAD THESE RUMORS!

jlschneck

Draining the coolant system from the bottom rad hose is definitely messy. If possible I would recommend performing the work in the driveway versus inside a garage. Get yourself the largest drain tub you can find. Pretty sure Lowe's/Home Depot sell them. Do your best to collect as much of the spent coolant as possible.

I used a round 5 gallon collection pan and a 3.5 gallon drain tub. Worked to collect most of the coolant but no doubt some got on the driveway. Have a garden hose handy to wash down/dilute any spillage.

JerpCherooke

So I am flushing my coolant as we speak. I have only been able to get like a 1.5 gallons of distilled water in the radiator and it just keeps over flowing. I didn't Uninstall the t Stat. Will that really make that big of a difference. If this is a 16 quart system, why can I only get like 8 quarts in?

Motojunky

The rest is in the block, heater core, and hoses. Start the jeep for a second or two and you'll pump some of it out. It's not too hard to disconnect the heater core hoses at the inlet and flush that out independently.

That said, you really would be better off if you could remove the t-stat and flush it all out very thoroughly with a hose. I understand that you're working in a garage, so you may have to just to repeated flushes with distilled water to get where you need to be.