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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
First we noticed gray/brown stuff under the cap of the radiator. Then trying to drive the vehicle 10 miles to storage, we only got half way when it overheated (saw steam come out from under the hood). We saw no coolant spilled under the hood but when it cooled down we found the radiator was empty.
Added one gallon water to the radiator and it was still not full and no water spilling on the ground anywhere. I began to suspect the water was entering the crankcase so I pulled the oil drain plug to verify my suspicion. Only oil began to drain, so I immediately replaced the drain plug: had to use a 1/2" drive breaker bar to remove the drain plug--what on earth do those quick oil change mechanics (monkeys?) think they are torquing down anyhow?
So back to adding the water. After a second gallon was added I heard water pouring onto the ground from an area on the passenger side beneath the upper radiator hose. However, the upper radiator hose was intact and dry. Water leaking somewhere beneath the hose. Reminds me of the time the plastic radiator tank in that same area split open about 5-10 years ago.
I still suspect a possible cylinder head and or cylinder head gasket problem due to the brown junk we found in the radiator a week or more before this latest breakdown. After the tow home, I noticed a very strange black ring on the very end of the tailpipe (and inside the tailpipe end it is pitch black also): see photos. I will begin the diagnosis by doing a compression test on all six cylinders and go from there. The vehicle still starts, runs, and moves like normal but, of course, can't drive it very far without coolant.
When it comes time to replace the radiator (which I suspect will be necessary) I will be tempted to purchase one of those all metal radiators I found last year online to replace the plastic style one. It will cost a small fortune to do so, but plan to keep this vehicle forever and should be worth it in the long run.
Edit: Has anyone installed the aluminum radiator made by Alloyworks? Thank you.
I don't see a crack under the oil cap (but it's dark in there) and I don't see "TUPY" unless there is black sludge covering the top of it. But like I said, definitely saw something brown when i popped the radiator cap a couple of weeks ago. Compression test was inconclusive (see photo), I was hoping to find a couple of adjacent dead cylinders which would have force me to remove the head and at least change the head gasket.
I don't have any faith in the "block sealer" products to take care of a cracked cylinder head, BUT it might be worth a try before tearing everything down after I at least replace the radiator. The "one star" reviews on Amazon for the aluminum radiator (listed for about $150.00) advise against its purchase as some buyers after a year or two find leaks. I'm still looking for an even more expensive radiator upgrade I found online a year or two ago which cost upward of $500.00. Don't know if its still available or what the reviews might find.
Could be a cracked head pressurizing the coolant system and a weak spot in the plastic end tank. I'd had 2 end tanks crack on my various XJ's over the years, they can be a bit touchy. Always replaced them with the cheap autozone ones and never had an issue so far.
I'd replace the radiator and then run an exhaust gas test on the cooling system.
Just a comment in passing. FSM says compression should be 120-150 psi with a max variation of 30 psi. Cyl 1-5 are within 10 psi. #6 is pretty high. Perhaps due to carbon build up. Likely not related to your cooling issue but something to check while you're in there.
Update: I had the special tool to disconnect the bottom trans cooler line (aluminum/gold color 3/8"). However, I could not pull the pieces apart after a lot of effort (and cussing). So I removed the radiator half way and disconnected the fitting where it entered directly into the plastic body of the radiator tank. With the radiator now removed completely, and the sun shining directly overhead into the engine compartment (about high noon), I could see all the tabs were all ready pushed back out of the way inside the line as I peeked inside. So I shot even more penetrating oil inside, then I twisted and pulled and twisted and twisted and pulled (this time without the tool) and finally it gave way and popped out. I never would have been able to get that kind of leverage on the fittings while bending over the fender/grill with only a couple of fingers wrapped around things and I don't see anything corroded inside the line. I believe the four tangs still are pressing against the metal tube even after the tool pushes them out of the way (not sure, just my theory).
With the radiator outside, I poured in some water and it poured out in a crack in the plastic tank just below the upper passenger side radiator hose. "Modern" automotive engineers are a-holes, the fittings are stupid and a radiator with a plastic tank is even worse.
I will probably remove the valve cover and see exactly what cylinder head it has, casting number, etc. and look for a crack (the valve cover gasket is leaking anyway). To be continued.
Update: Removed the valve cover which inside was "clean" but pitch black in color. The cylinder head surface also appears "clean" but is also pitch black in color. I found the casting number 0331. After the vehicle was in the shade, I got out the trouble light to inspect the cylinder head area between cylinders 3 and 4. At first, I saw no signs of cracking, but manipulating the trouble light at different angles, I believe I found a ragged crack right there in the middle where the newer heads have the word "TUPY" cast. The crack looks "closed" and it's almost invisible and would be completely unnoticed by the naked eye unless one knew exactly where to look and what to look for. Hard to believe what appears to be such a trivial defect could ever cause a problem. I'm living in Mexico for the past dozen years or so. I will visit some local wrecking yards, hopefully tomorrow to inquire if there are any of the "TUPY" cylinder heads on the shelf. I don't believe the crack would show up in a photo so I just posted overall photos of today's work.
I will also be looking for a socket to remove the head bolts. Some say to use a deep twelve point 1/2" size, others say to use a 13 mm size. Tools are so expensive these days, and a lot of junk out there. Oh well, I hope I find something that works.
A 1/2 deep 12 point socket fits perfectly fine on the headbolts...a large breaker bar is required. You will need a decent 1/2 drive torque wrench to reinstall. Nbr 11 ...front drivers side passes through the cooling jacket so you need some prematex high temp sealant and it only gets 100 ft ibs at the end...all rest 110 Take a picture of headbolt locations because two of them have the extensions that hold the valve cover gasket in place. Also get new bolts..not worth the 40 bucks to reuse headbolts. Also if you get new bolts...chop off exactly at nut and cut a slot for a screwdriver on 4 bolts to use as alignment studs when reinstalling that stuper heavy head. The very last bolt on drivers side at the firewall will not clear the head/firewall...remove it with the head..hold in place with rubberband during removal and install
Last edited by bluejeep2001; 05-02-2024 at 01:19 PM.
I got one and my temps dropped a lot verses the stock aluminum / plastic one the new one is thicker too, all metal good stuff. my jeep friend also bought one about three years ago, same summit radiator, his still runs great.
04-30-2024, 12:50 PM
Blew Out Radiator Again 2001 XJ
