Sep 21, 2015, 04:46 PM
Last edit by: IB Advertising
See related guides and technical advice from our community experts:
Browse all: Engine Diagnostics
- Jeep Grand Cherokee WJ 1999 to 2004 Why is Car Overheating
Guide to diagnose trouble and recommended solutions.
Browse all: Engine Diagnostics
Overheating after heater core bypass (NEED HELP!!)
Thread Starter
Member
Joined: Mar 2012
Posts: 187
Likes: 0
From: Las Vegas, Nevada
Year: 1990
Model: Cherokee
Engine: 4.0L 6Cyl L8
Just got back from a 8 or so mile drive, fine all the way down there (with no stops that is) but heated up again on the way back after a few lights. 
CF Veteran
Joined: Dec 2011
Posts: 4,006
Likes: 1
From: Pasadena, MD
Year: 1987
Model: Wagoneer
Engine: Renix 4.0
if it is just overheating at lights, its your mechanical fan clutch. that is what your cooling system relies on to pull air through the radiator at a stop. just because it spins doesnt mean it is good.
Thread Starter
Member
Joined: Mar 2012
Posts: 187
Likes: 0
From: Las Vegas, Nevada
Year: 1990
Model: Cherokee
Engine: 4.0L 6Cyl L8
Originally Posted by jakbob
if it is just overheating at lights, its your mechanical fan clutch. that is what your cooling system relies on to pull air through the radiator at a stop. just because it spins doesnt mean it is good.
Last edited by Johnthepanpire; May 23, 2012 at 08:41 AM.
Thread Starter
Member
Joined: Mar 2012
Posts: 187
Likes: 0
From: Las Vegas, Nevada
Year: 1990
Model: Cherokee
Engine: 4.0L 6Cyl L8
Got a new clutch and it ran cooler but still 15-20° over operating temp. Taking her on a longer drive and see how it goes.
I'm still thinking it's the temp sensor giving a high reading too?
I'm still thinking it's the temp sensor giving a high reading too?
Member
Joined: Jul 2010
Posts: 194
Likes: 2
Year: 2000
Model: Cherokee
Cooling fan should come on at a certain temp even with a/c off.
Your radiator could be plugged up, even though you said it was flushed. I flushed my old radiator once with 2 bottles of flush, didnt help much. Ended up emptying and removing the radiator and sprayed brake cleaner inside, swooshed it around and drained it out, a WHOLE bunch of gritty rusty sludge came out. I had found my overheating issue.
Your radiator could be plugged up, even though you said it was flushed. I flushed my old radiator once with 2 bottles of flush, didnt help much. Ended up emptying and removing the radiator and sprayed brake cleaner inside, swooshed it around and drained it out, a WHOLE bunch of gritty rusty sludge came out. I had found my overheating issue.
CF Veteran
Joined: Oct 2011
Posts: 4,440
Likes: 3
From: Seal Beach, CA
Year: 1996
Model: Cherokee
Engine: 4.0 HO Straight Six
And the most amount of stress is put on the cooling system when at idle, since there is no air flowing through it all, except what the fan brings through it. So good call on replacing the fan clutch.
Did you replace your radiator too? It may be time to do that if your gauge is in fact reading correctly.
CF Veteran
Joined: Mar 2010
Posts: 47,923
Likes: 38
From: Broward County Fl.
Year: 1989 xj sport 2dr
Model: Cherokee
Engine: 12 hole bosch Injectors
Sensors in our XJs are known to crap out after a while. And that sensor in the rear driver's side is what gives your gauge its reading. I would grab an infrared temperature gun and make sure that your gauge is reading correctly. If not, it's time to replace that sensor
And the most amount of stress is put on the cooling system when at idle, since there is no air flowing through it all, except what the fan brings through it. So good call on replacing the fan clutch.
Did you replace your radiator too? It may be time to do that if your gauge is in fact reading correctly.
And the most amount of stress is put on the cooling system when at idle, since there is no air flowing through it all, except what the fan brings through it. So good call on replacing the fan clutch.
Did you replace your radiator too? It may be time to do that if your gauge is in fact reading correctly.
CF Veteran
Joined: Mar 2010
Posts: 47,923
Likes: 38
From: Broward County Fl.
Year: 1989 xj sport 2dr
Model: Cherokee
Engine: 12 hole bosch Injectors
SO, after going though posts on here for 3 days trying to see if I could figure out what was wrong I'm still lost.
I just got done giving her a MAJOR tune up (spark plugs, wires, dist. cap, rotor, ignition coil, fuel injectors, valve gasket, exhaust gasket, scrubbed the throttle body clean, TPS sensor, rad. fan temperature switch, new relay, new fuses, starter, brand new exhaust system, thermostat, air filter, oil change, rad. flush, new water pump, new rad. cap, loads of new hoses, and a $hit load more)
Anyways, after all that everything was running better then it had in quite awhile. The temp never rose above 210 ever.
Then when replacing some hoses the heater core got broke so we had to bypass it. I lost most of the coolant then so I flushed it and filled it back up (75% coolant 25% water) and it's overheating now.
It only overheats in slow traffic like in parking lots and at stop lights. I went 30 miles on the freeway with it staying right below operating temp. And the electric fan only comes on when the a/c is turned on (which I can't use right now, needs to be recharged :P)
I was reading that it could be the fan clutch so I've been checking it and I can't really feel a difference between when it's hot and when it's cold. When I spin it, it only goes down one blade so I'm not sure that's bad??
Either way I never had this problem until after I bypassed the heater core and had to flush the system.
Any help would be much appreciated!
I just got done giving her a MAJOR tune up (spark plugs, wires, dist. cap, rotor, ignition coil, fuel injectors, valve gasket, exhaust gasket, scrubbed the throttle body clean, TPS sensor, rad. fan temperature switch, new relay, new fuses, starter, brand new exhaust system, thermostat, air filter, oil change, rad. flush, new water pump, new rad. cap, loads of new hoses, and a $hit load more)
Anyways, after all that everything was running better then it had in quite awhile. The temp never rose above 210 ever.
Then when replacing some hoses the heater core got broke so we had to bypass it. I lost most of the coolant then so I flushed it and filled it back up (75% coolant 25% water) and it's overheating now.
It only overheats in slow traffic like in parking lots and at stop lights. I went 30 miles on the freeway with it staying right below operating temp. And the electric fan only comes on when the a/c is turned on (which I can't use right now, needs to be recharged :P)
I was reading that it could be the fan clutch so I've been checking it and I can't really feel a difference between when it's hot and when it's cold. When I spin it, it only goes down one blade so I'm not sure that's bad??
Either way I never had this problem until after I bypassed the heater core and had to flush the system.
Any help would be much appreciated!
Junior Member
Joined: Aug 2011
Posts: 90
Likes: 0
From: Willowbrook, IL
Year: 1994
Model: Cherokee
Engine: 4L inline 6 cylinder
My XJ temperature will creep to the ¾ mark and then the aux. fan kicks in and brings it down below 210° when standing still and temperature is over 100°.
That is with new radiator, hoses, t-stat, clutch fan, new 50%-50% coolant, and 97+ aux. fan.
That is with new radiator, hoses, t-stat, clutch fan, new 50%-50% coolant, and 97+ aux. fan.
Newbie
Joined: Sep 2011
Posts: 12
Likes: 0
I had a similar problem and checked everything too they said I had a leaky head gasket pressurizing the coolant system so I even rebuilt the motor first drive with new motor overheated I was going crazy so I swapped the radiator out (the whole time saying I've already flushed it 3 times they're crazy that's not the problem) well I hate being wrong but haven't had a problem since