So I have been working on this Jeep for awhile, its a 2000 4.0L, 180K miles.
- It was overheating, I took it to a shop, guy says he will replace my radiator.
-Got 2 miles down the road and it overheated again.
-Towed it back to my house, figured out there was no thermostat
-replaced thermostat and waterpump myself. still overheats very quickly.

note: heater core is bypassed

Please help with any suggestions, I would love to get this Jeep back on the road this month otherwise I have to scrap it before I move

Thanks!

 

And you don't have water in the oil or oil in the coolant?

Signs of a bad head on that motor..?? which I believe the 2000 model year was known for ..

 

I agree that a cracked cylinder head is a definite possibility.

The #1 symptom of a cracked 0331 head is "unexplained coolant loss" Are you experiencing that?

It sounds like you possibly just bought this XJ as you had no prior knowledge that it had no thermostat. The prior owner likely took it out as he had no clue as to what was happening....

I would first look through the oil fill cap with a pressurized cooling system (cooling system pressure tester) and see if you can see anti-freeze seeping through the head in the cylinder 3-4 area, which is where the 0331 always cracks.

 

The oil and coolant appear to be normal, although I have been suspicious it was the head...really operating on wishful thinking before I take that leap.

I have had the Jeep for 2 years, when the guy replaced the radiator it appears that he did not put a thermostat back in...since then I have just been doing what I can myself because that way at least I know whats going on first hand...and I am learning as well.

About the pressure check, is that something I can do myself or should I get it diagnosed? I can get it to a shop before it overheats, i live near several.

Thanks for your help!

 

Also, it doesnt appear to be leaking coolant at all. The one concern I have is it never takes it from the reservoir either which I find strange...
But I will admit, I am still a novice at best when it comes to repairing vehicles, replacing the water pump is definitely the most in depth repair I have done.

 

Mine was overheating after replacing heater hose. I burped the radiator and that solved the problem. Mine is a 2000 also.

 

May not be your issue....but check your fan clutch.

 

"Not running a t-stat will cause overheating" is a myth. The sole function of a t-stat is get coolant/motor temp up to the stat's designated temp as quickly as possible. Once the stat is wide open (same as no stat), it does nothing.

U say 2 miles down the road it overheats after installing a new rad, water pump and t-stat. Is that driving very slow for 2 miles and it over heats? If so, could be a bad fan clutch as stated. If driving at hi-way speed, it shouldn't need any fan(s) at all to remain cool. Definitely do the pressure test as recommended and verify the goofy factory temp gauge reading with a infrared point-n-shoot temp gun.

 

when i got my jeep i had to put a new water pump on it and it overheated, so i put a new thermostat, radiator, and fan clutch on and it still did. So i bought a flush kit from autozone and flushed it and it hasnt overheated since and that was last year so i would try that.

 

Since it overheated so quickly, I wonder if there was air behind the 'stat, causing it to stay closed.

 

Impossible for air to be behind the stat (unless coolant level is below the stat). The stat hole in the head has a dime sized hole beside it (the coolant bypass hole) that allows water/air to flow both behind and beside the closed stat the moment the motor is started. The stat will open at it's rated temp in both air as well as in water.

 

I hope it's not the head. If it is, you can blame Chrysler for that.

 

Thanks for all the help folks, I am going to check the pressure and most likely replace at least the head, or more if that is what it takes. I wanna keep this jeep, I love the thing...anyone know a good jeep guy in the LA area I am all ears!

 

I think it needs burping, because I had the same problem with a CJ. Couldn't get water into the bottom of the engine after a radiator replacement. I need to burp my 1990, but there's no cap! How do I do it?

Also, there's a good Jeep guy in Palmdale, and he's reasonable and honest.

Kim's Auto Repair Service.

Can someone help me with the burp job on the '90 Laredo? I just bought it; have a YJ and a 2005 Liberty 4X, and just sold my 1984 CJ to my Son-in-Law.

 

Not quite sure I understand "couldn't get water into the bottom of the engine". When the rad/motor is filled with coolant, they fill from the bottom up. Most of the air escapes as the system is being filled. There may be a small amount of air at the very upper portions of the head or rad, but that usually exits at motor start-up. The best/easiest way to "burp" what little air may remain in either open/closed cooling systems is to let the motor idle with the bottle/rad cap off 'till the motor reaches temp/stat opens. Keep the rad completely full (open system) or the bottle about 1/3 full (closed system) while idling. After stat opens (top rad hose hot), replace either cap with a new one.