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Blown head gasket?

A

AlfredoAlonso

NAXJA Forum User
Location
Miami, FL
Hello,

I am, as of now, the owner of a 2000 Cherokee 4x4 4.0 in Sienna Pearlcoat with about 130k on the dash. The car came with a few minimal mods and minor rust.

However, the car had been sitting for a while before I purchased it (Around a year). I took it for a test drive and everything was working like normal. After that, I was driving it home (which the drive was about 80 miles), and around 40 miles in the engine started to overheat, so I stopped and had the car towed back to my usual shop. The next day, we put in a new thermostat and filled the car back with coolant and everything seemed to work normally at idle. It was keeping its temperature with no issue at idle for a long time. Then, I took it for a short drive and within around 5 minutes it started to overheat again. We suspected it was the water pump, but upon it's removal it seemed to be in good condition, and there seems to be no blockage in the radiator. Our next prediction is that I bought the car with a blown head gasket, but wanted to see if there are any other options as to why it is overheating before I spend a lot o money tearing the engine apart. Also, what I find weird is that if the head gasket was blown it should've overheated withing the first couple minutes of driving, not 40 miles later.

The radiator on this car is not original, it is a 4" aluminum radiator, and it has 3 fans that are on a switch, which are all working and are always left on. Any imput is appreciated. Thank you very much!
 
Your fan set-up sounds very "questionable", but do some searching because the 00-01's are notorious for head problems that cause over-heating.
 
My 99 was leaking fluid into one of the cylinders. I only noticed coolant exiting the exhaust pipe and didn't see the usual fluid around the head perimeter.
 
A couple of search terms you need: "0331 head" and "TUPY head"

The 0331 head is prone to cracking. If that is indeed what you have then it is likely that is your problem. The TUPY head is the most popular solution.

Do some research on the 0331 and figure out if that is indeed what you have. Once you figure out that detail you can then determine what sort of solution you should be looking for (new head, or other possible suspects).
 
Did the shop do a pressure test on the coolant system? Also, might replace the radiator cap. They do go bad. Are you loosing coolant? Also, I'd replace the water pump. It might look good, but the impellor might be getting loose. I did have this happen on a Dodge Neon. When it heated up, then it would spike in temps. The impellor nearly fell off.
I might also try a flush. See what junk comes out. I am in this process with a 2000 XJ too. Yes, I might have a cracked heap or blown head gasket. I will not on the engine in my '98, I replaced the freeze plugs. The rear one on the engine block, I found a bunch on built up junk on the outer cylinder wall.
 
Thank you all for the input. We went ahead and disassembled the head, as we had done all the previous tests we could think of, and this is what we saw. My mechanic says this is definitely the cause of the overheating, but just wanted to run it by here to se if you have any input regarding it. Also, he suggested taking the head to be machined, to make sure it is well. However, I do have an 0331 head, and i'm afraid of it not lasting as long as it should and having to repeat this whole process again.

Also, the engine block has a sticker from Jasper stating that the engine was rebuild (or changed, haven't looked into it), and another sticker was on the fan shroud stating this was done when the car had 101,000 miles (currently at 130,000) Not sure if this is relevant to the situation just putting it out there.

Any input is recommended as I don't have too much prior experience when it comes to pulling an engine apart.

Working on attaching images, not sure how to do it ATM.

Thank you!
 
Most likely the engine was changed for the same reason, and another crack is almost inevitable. Exact same scenario happened to me with an 01.
 
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Sent from my iPhone using Tapatalk
 
I'd look for the "TUPY' letters on the casting. It should be on the inside area of the VC near the 0331 casting number. If it doesn't, I'd get a 'TUPY' head and have it reconditioned. I think '02-'06 are TUPYs. I might call Jasper, but I don't know their warranty. I would guess time and second owner are a 'no. Also, I'd get new head bolts.
 
A couple of comments on cracked heads.

1. Cracked heads are not unique to Jeeps. There have been a number of different brands of cars over the years that had reputations for "cracking heads". One brand that I owned, a Toyota with a 2.0L 4-cylinder OH camshaft had the reputation for cracking heads. What I found was the exhaust valve head runner was undersize to keep the exhaust gas temperature high in order to reduce NOX emissions. That approach creates extremely high heat in the exhaust runners and that's where the heads typically crack. My fix was to SLIGHTLY enlarge (i.e. port) the exhaust runners under the exhaust valves to improve the exhaust flow of high temperature gases out of the head. Result? No more cracked heads.

2. When I bought my used 2000XJ, I knew it was loosing coolant and suspected a leaking head gasket and/or a cracked head. I pulled the head off the engine and then stripped all the valves and springs from the head. Then I had the head pressure-tested for existing cracks and also had the head Magnafluxed for cracks that were just starting. The head was good and then I had the head resurfaced for gasket sealing. When I got the head back from the machine shop, I lightly ported all the intake/exhaust runners paying close attention to the exhaust runners to get more exhaust flow out of the head. Then I narrowed the valve seats in the head and relocated the head's circular seat contact areas so they made contact near the outer diameter of the valves. Since valves get hotter than a cooled head, the valve diameters expand more than the head seat diameter does. So when the valve-heads heat- up and expand in diameter, the head's circular seat contact area moves inward on the valve head but stays on the valve seat. I've put on about a 100,000+ miles on my 2000XJ since that work and it runs nice and cool and gets through emissions without any problems.

Hope this helps someone.

Best regards,

CJR
 
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