Still overheating!!

91 XJ 4.0 HO auto tranny

i've replaced the t-stat with the 190 temp t-stat
replaced upper and lower hoses
just replaced the thermal fan clutch
radiator cap

the @#$@#$^@# thing still overheats at highway speed

i don't thing it's getting enough water to tell you the truth. is there any way to check this

overheating at highway speeds usually indicates the radiator is mineralized and plugged.

Either take it out and take to a radiator shop to have it rodded or just get a new one.

Pretty much what he said, did the new lower hose have the spring in it ?
You can try this, drain the system, refill with water and prestone 7 hour flush then follow the directions. That stuff removes alot of build up both in the rad and in the block. Also did you bleed/burp the system to get all the air out ?
Is your fan belt tight enough ?
Not only do water pumps fail with bad seal and bearings but they also fail because the vanes in the pump itself are gone, usually thru corrosion but the only way to check is to remove the pump and eyeball it and if you do that you might as well put a NEW one on [not a rebuild]. If thats an original or been on there a few years then it may be time....
If you do the flush remember to leave your heater on hot so the cleaner gets in there too. Refill with coolant and DISTILLED water.

OK, i took the rad cap off and started the vehicle and noticed that the coolant was right at the top of the radiator. as i let the engine run the level would rise and the coolant would spill out of the top.

I really get the feeling that the block isn't getting any coolant for some reason.

How do i burp the system?

Best thing I did to get rid of my overheating on my '92 XJ was replace the radiator with a GDI 3 core. I got it off of Ebay for about $140. On the highways, with the AC on, I hover right at 210. And that's here in the AZ 100+ temps. At night, it won't come close to 210 mark. I'm still using a 190 thermostat too.

rockethound said:

How do i burp the system?

Click to expand...

Newer open systems like your 91 shouldn't need to be burped.

rockethound said:

OK, i took the rad cap off and started the vehicle and noticed that the coolant was right at the top of the radiator. as i let the engine run the level would rise and the coolant would spill out of the top.

I really get the feeling that the block isn't getting any coolant for some reason.

How do i burp the system?

Click to expand...

It's normal for the coolant to spill out from the top if you have the cap off while the engine's warming up.
I think your problem's a clogged radiator, and the overheating on the highway is a telltale sign of that especially if the engine runs at normal temps. in the city.
The '91+ 4.0's come with an open cooling system that's "self-burping", so you don't need to do anything. If you replace the coolant, you need to make sure you also have enough in the expansion bottle because that gets sucked back into the cooling system as it's burping itself.

Re: Still overheating!! (SOLVED!!!)

I replaced the radiator, waterpump, tstat, upper and uppper and lower hoses and one or a combination of those did the trick. Now it's just getting the belt tight again.

Re: Still overheating!! (SOLVED!!!)

rockethound said:

I replaced the radiator, waterpump, tstat, upper and upper and lower hoses and one or a combination of those did the trick. Now it's just getting the belt tight again.

Click to expand...

I'll lay money that it was the new radiator that did the trick. The t'stat, hoses, fan clutch, and radiator cap certainly didn't according to your first post. Water pumps usually still work even when they leak and the pump shaft wobbles due to wear, so it's very unusual for an engine to overheat because of a bad water pump. If the serpentine belt is so loose that it's slipping on the water pump pulley, then the water pump won't work to maximum efficiency and the belt will screach.

Re: Still overheating!! (SOLVED!!!)

my '91 used to overheat so i just rigged a switch for the auxilary fan. no more probs