88 XJ Running Hot Sometimes

(88XJ automatic w/ 4.0)

Within the last couple of weeks I've replaced my water-pump (auto-zone part # BWP-724), thermostat and overflow coolant bottle.

#1 strange issue: When the Jeep is first warming up for the day, when it gets to operating temperature it makes a whining/whistling sound for about 2-3 minutes and then stops. The pitch does not increase/decrease with the engine RPM, it only gets louder and quieter. It's very hard to hear over the radio. I tried to isolate it with the ole trusty screwdriver to the ear... but all I can tell is that it "SOUNDS" like it's coming from around the throttle body. Tried the brake cleaner looking for vacuum leaks and couldn't find anything. I'm wondering if it could be the new water pump.

#2: The engine runs hot at highway speeds. I can drive all day long at 45-50 MPH and it never gets over 210. But the minute I jump on the highway it climbs. I never drive far enough for it to get above about 225 before I shut it down.

I'm going to try flushing the radiator for the heating problem sometime today or tomorrow... I'm just really hoping I dont' have to pull that water-pump off again. It's not hard, just so tedious... especially in this gawd-awful HEAT!

Notes: Fan shroud, fan clutch, fan motor, electric fan, water bottle and cap and all hoses are GOOD. Replaced water pump because it was leaking from the weep-hole. Replaced thermostat ... cos... why not? (195 degree) Normal operating temperature before changes, even on the highway, was around 210.

Any thoughts you may have would be greatly appreciated.

Thanks!

Well you said your going to try flushing the rad but if that doesnt work for the heating problem you should really consider going to the open cooling system.
My '88 used to run hot and overheat until I changed out the closed system for an open one.
It's really not hard to do.And the parts of cheap.

This may sound wierd, but take a look at your radiator and make sure there are no missing fins. My 92 would heat up pretty good on the freeway like yours does. I found that most of the fins behind (in front of) the mechanical fan were gone! The ones behind the electric fan were getting there too.

It now has a new 3 core radiator and the temp only goes over 210 when crawling on a trail or sitting in traffic on a hot day. Even then it's barely the width of the needle over the 210 mark.

Chero-King said:

Well you said your going to try flushing the rad but if that doesnt work for the heating problem you should really consider going to the open cooling system.
My '88 used to run hot and overheat until I changed out the closed system for an open one.
It's really not hard to do.And the parts of cheap.

Click to expand...

Well, I have considered it... although, I know a lot of guys running the OEM setup with no problems... Nevertheless, there are plenty of write-ups on this line of questioning already, so we don't need to start another one. And even though I appreciate your input, my question remains the same...

Kuasimodem said:

This may sound wierd, but take a look at your radiator and make sure there are no missing fins. My 92 would heat up pretty good on the freeway like yours does. I found that most of the fins behind (in front of) the mechanical fan were gone! The ones behind the electric fan were getting there too.

It now has a new 3 core radiator and the temp only goes over 210 when crawling on a trail or sitting in traffic on a hot day. Even then it's barely the width of the needle over the 210 mark.

Click to expand...

Thanks for the information... I've considered replacing to a 3 core anyway... I just think it's awful fishy that it started doing this AND making that strange whining sound the same time I replaced my water pump. Of course then again, we all know Jeeps need no rhyme or reason to do most things. :lol:

Changing to a open cooling system is not a cure for over heating.
A closed system will never loose coolant when working properly.
Open systems do lose some from evaporation and because they are open need to be serviced more.
They do not cool better.
It can be a pain to get all the air out of a closed system and that sounds like your problem.
Also the correct thermostat is important, you want one with a air bleed hole in it or drill one in your self about 1/16.

One other thing did you get the correct pump? I think with or without A/C makes a difference because they turn different directions because of the way the belt runs.

langer1 said:

One other thing did you get the correct pump? I think with or without A/C makes a difference because they turn different directions because of the way the belt runs.

Click to expand...

I have read this comment and others about the correct rotation of the blades in the pump.

When i called hesco about pricing on a new pump, I asked about the model numbers and the direction of the blades etc. Hesco said ALL pumps for the 4.0 and 4.2 are the reverse rotation pumps and there isn't one for the 4.0/4.2 with a forward rotation blade.

Anyone have confirmation on that info...Like a picture of both style pumps?

I'm fighting this heating problem also.

I've read writeups on this before and the model # I listed is the one that's been used many times before... it's a reverse rotation pump from Auto-Zone...

TXHillsboy said:

I've read writeups on this before and the model # I listed is the one that's been used many times before... it's a reverse rotation pump from Auto-Zone...

Click to expand...

Probably the same pump I have on there now.

Was just curious to see pics of both. Hesco said ALL the pumps are reverse rotation.


Kinda reminds me of the temp switch for renix systems when doing an open cooling system upgrade. Someone posted about using a corvette switch, and 2 other switches...Posted on 6 forums. Finally someone tested all 3 switches and NONE of them worked correctly. thus internet folk lore.

Funny... I was just having that SAME convo with my friend this morning. I just wanna fix it!

Hoping to get this thing flushed today...

Anyone else have any thoughts or suggestions?

Did you do the flush to include your heater? Upper and lower lines, heres a site that might help.http://www.olypen.com/craigh/tech.htm
Has all the great tips for the flush, use and care of closed system and some really great elctrical upgrades. Good Luck.

i had the sam problem except the coolant bottle leaked. so i got a new on and the next day there was a line going down my street to where i parked my jeep. thought nothing of it? my radiator blow a hole and i realized this driving my friend home it stalled. when i went to look at the radiator there where no fins on it it was just paint.:scared:

Okay, I know it's been forever... but I've been working a lot and my wife went out of town...

Anyway... the overheating problem was caused by a crack in my thermostat housing. I replaced it, the coolant bottle, flushed the radiator/coolant system and everything is fine.

The whistling noise was a bad o-ring on the #6 fuel injector. Good ole' B-12.

Anyway, just thought I'd post up and let you guys know that it was all good to go!

Thanks again!

Yeah, my old radiator blew a hole in July when I got back from Chicago - so happy it didn't happen out there! I flushed it a few days earlier. When I pulled the old radiator out the fins were basically dust, you'd touch them and they would flake off.

Before I converted my jeep over to an open system I used to have alot of trouble with the cooling system getting an air bubble trapped in it and gettin air locked. I would take the hose coming out of the t-stat housing lose and pump water into it until water started coming back out into the reservoir bottle. This would usually fix my cooling woes.