Yet another coling question guys... sorry.

I looked all over the site and couldn't find a problem quite like this one.

When idling this 88 cherokee runs at the normal operating temperature - about 195. But when driving at full speed or especially up hills, it likes to run real hot. Not overheating but real warm, about 220-240. If taken back down to idle, it'll just come down to normal operating temperature. It usually will only hit 240 for a second or two when climbing and then drop down again.

My cooling system is the closed loop but I have an aftermarket aluminum pressure bottle that feeds into a second open loop type reservoir and there isn't an abnormal amount of exchange between the two bottles. In fact, the pressure bottle is always kept completely full and when the system needs to purge or bring in coolant for temperature adjustment, it exchanges through the extra reservoir. (see pic attached).

Any ideas here folks? This is really perplexing and troublesome. Why would it run at normal temperature when idling or traveling at slow speeds but want to run hot at highway temps?

 

Sounds to me that the water is not being cooled enough when its flowing faster through the radiator. Have you checked the upper and lower hoses making sure one is not collapsing under pressure? I would check hoses, clutch fan (does it spin a few times when you shut the motor off?) and maybe trying to back flush it with that $3.99 Prestone kit...Tj

 

Yeah. Checked the hoses. Not collapsing. Here's a question though. If you squeeze the upper radiator hose when at operating temperature, how should it feel? Hard? Squishy?

 

On mine its Squishy and that's at 195 degrees. You may also have a clogged radiator. Have you tried putting the heat on and driven it like that up a hill?

 

No haven't tried that. What will that tell me?

 

The water will flow through the heater core and may stay in the radiator longer to cool it...Tj

 

Gotta bump this up.

Is the consensus that this would possibly be a clogged radiator? Bad water pump? Possibly malfunctioning T-stat? I'm still real fuzzy on this.

 

What about the heater core?

 

bad radiator will make it hot on the highway or under load and normal at idle. bad fan clutch is just hte opposite.

 

I've seen same symptoms with nothing wrong with cooling system, but a mostly clogged cat converter. Just something to check.

 

The previous engine had sever blow by and I wonder if it could have clogged the cat. The cat was installed right before I bought the jeep and I put about 600 miles with bad blow by (1qt out the air cleaner every 50 miles). Ever since the new engine was put in it's been running hot. What do guys think?

 

Nothin' huh?

 

The wifes 95 did that, anything over 55mph and it would overheat.
You could open the heater core and fan on high and be ok at 65mph.
We replaced the radiator and that cured 95% of it except on 100 degree days climbing mountains in the ozarks. Then it would over heat again.

 

A friend had an early XJ 4 banger that did the same thing, turned out that when they changed from V-belts to Serpentine the fan rotated in the opposite direction. His fan had a junkyard replacement with a later fan, so it blew instead of sucked.

Which really sucked just the way you described. Hope it helps.....

 

First thing to do is check it with an aftermarket gauge you guys duhhhhhhhhhhhhhh. Use your heads then proceed with simple things first. How many times will it take for you guys to figure this out when giving info.simpletons.:mad :