andrewmp6

Does your ac work now or not?If the ac works the condensor is fine if it don't then its probably broke also.

extrashaky

If your radiator is not leaking, I'm not sure you really need to replace it. A new one may not solve your overheating problem.

Are you seeing brown sludge? That's probably not rust. That's what is left behind when the water boils out of antifreeze and leaves the residue behind. That stuff can build up in the engine block and decrease the life of your water pump. Flushing will only get some of it out.

I don't want to frighten you, but my 2000 had similar symptoms to yours, and it turned out to be the infamous 0331 head crack. You have a '99, which may have the 0331 head casting. A LOT of '99-'01 XJs are ending up in the Pull-a-Parts now looking like nothing is wrong with them, but if you pop the top on the coolant bottle you'll see it full of that sludge.

What happened with mine was that when the engine was hot, the crack would sometimes open and allow exhaust gas into the coolant. The hot exhaust gas would boil the antifreeze, causing inexplicable mild overheating and resulting in the brown sludge. The sludge killed my water pump, so I replaced it and flushed the system (thinking the water pump was the problem) only to have the overheating issue come right back. I eventually ended up replacing the entire cooling system, radiator and all, to no avail.

Because it was an intermittent problem, it wasn't easy to diagnose, but I will make a couple of suggestions to you. First, take an oil sample and send it off to Blackstone for analysis. If they find water in your oil, you know you have some sort of head problem, and they can detect it before you can see it. I will never do another oil change without sending a sample to Blackstone.

More importantly, either buy a combustion leak tester (or find a shop that has one) to test for the presence of exhaust gas in your coolant. You can order one from Amazon for about $50. You draw coolant up out of the radiator into a plastic chamber and add some detection solution, and if you have exhaust gas in your coolant the solution will change color.

If that happens, it's almost certain that your sludge and overheating are caused by a head problem. Then you have to figure out whether it's just a blown gasket or a cracked head. Either one is a painfully expensive prospect, but it's better to catch it now before you get water in your oil causing further damage to the engine.

And if neither test comes back positive, you've at least ruled out the head problem and can then start trying to find the problem in the cooling system. I wish I had done those two tests before throwing so much time and money at the cooling system on parts that didn't really need to be replaced.

The ultimate outcome for mine was that the head problem progressed to the point that I was having oil pressure problems because of water in the oil. Instead of throwing money into a new head on a 160K mile block I was no longer sure about, I just pulled that engine and replaced it with a Golen stroker. So it has a happy ending.

Pelican

Wow!

Kingfisher

^^^
And if you have no coolant leaks maybe all you need is a good flush.

HarleyRob

yes ac works fine. what is described above is exactly what mine seems like it is doing. i may b mistaking this sludge stuff for rust. ihad the water pump replaced not long ago. the radiator isn't leaking currently.

i did notice today that hose from overflow tank (whatever u call it) to radiator by cap was packed solid with sludge crap so no coolant moving one way or other. i replaced it with new hose. could that have caused slight over heating?

HarleyRob

oh, and who/what is "blackstone"?

HarleyRob

I'm starting to think i have a cracked head. i remember when the water pump went out it went way hot on gauge (all way to right). i drove the jeep just a bit further while hot. and then have to drive it several days later to mechanic.

Basshark7

[QUOTE=Pelican;2899881]Why does everyone think the OP has a separate transmission fluid cooler? Why are we talking about changing the trans fluid?


Everything you have said has been correct. Why do I think the OP has an auxiliary trans cooler? Because the OP stated he has the normal radiator and a smaller one and the AC condenser does not look like a radiator to me. I very well may have misinterpreted what the OP was saying. Both my 98 w/upcountry package and my 00 w/tow package came from the factory with the auxiliary trans cooler and both are automatics. I'm not explicitly telling him to change the trans fluid but to check it. He asked how to tell if it (the auxiliary trans cooler if he has it) needed replaced. I believe his trans fluid will be fine. And the only reason to mess with the auxiliary trans cooler (if he has it) is if it got damaged in the incident with the deer. I hope this helps to explain my thought process.

also the link in one of my previous posts is for the FSM cooling system section from Morris 4x4 Center.

Basshark7

Blackstone = Blackstone Labs (www.blackstone-labs.com)

Blackstone Labs provide oil analysis. You have to send them a sample of the oil you want checked. The report they give you will show you all the things in your oil that you can not distinguish with the naked eye. Example: My engine oil is hazy. Ship off a sample to Blackstone and they tell you what the contaminant(s) is/are.

extrashaky

More likely the overheating caused the sludge to plug the overflow hose. That sludge likes to collect right at the radiator cap.

What Basshark7 said above. And here's a sample of an oil analysis. This one came from my BRZ, but it gives you a good idea of what it looks like. There are more examples on their website of reports where things went bad.

nardey11

I realize this thread is 2 years old and I sorry for reviving it. I have the upcountry package on my 2000, the ac doesn't work and I want to replace the condenser, the radiator looks pretty bad so I want to replace that too. It does have the auxiliary trans cooler so do I need a different type of radiator?

Basshark7

The Radiator will be the same it will just have a few extra steps to disconnect the auxiliary trans cooler from the radiator. Also have someone vac test the compressor, make sure your seals are still good.

mschi772

EDIT: Unnecessary.