NAXJA Forums -::- North American XJ Association  

Go Back   NAXJA Forums -::- North American XJ Association > NAXJA Unibody Jeep Technical Forums > Jeep Cherokee XJ (1984 - 2001) > OEM Tech Discussion
HOME Member FAQ Sponsor Info Rules Bylaws E-Mail

OEM Tech Discussion Forum for OEM (Original Equipment) or stock XJs and MJs.

Reply
 
Thread Tools Display Modes
  #1  
Old July 15th, 2019, 15:04
NXJ4CB's Avatar
NXJ4CB NXJ4CB is offline
NAXJA Forum User
 
Join Date: Oct 2007
Location: San Diego
Posts: 12
Overheating solved

Hello,


Bear with me, I rarely post. I usually just read threads for the wealth of knowledge here.



I believe I have stumbled across the cause of our engines running hot. Like so many others I've tried everything. Here is my setup and after I'll explain my theory:


2000 XJ 4.0, 33's, 4.10 gears



CSF 3 row radiator.
Flowkooler Highflow waterpump.
Hesco High Flow thermostat housing.
180 Deg. Stant superstat thermostat (drilled with 3/16 hole).

13 inch Spal pusher fan in front of the condenser passenger side.
Ford Explorer aux trans cooler in front of the condenser driver side plumbed in series after the radiator.



I, like many others have gone down this rabbit hole for years and was discussing it yet again with a co-worker who figured it out. He determined that with this setup that the majority of coolant is passing through my heater core and not the radiator. After calling him insane, I tested this theory by installing a valve in the thermostat housing outlet to heater core hose and shut it off.



My temps immediately dropped from 220 at idle with both fans running to 185. So, in effect i blocked the heater core and forced all of the fluid to flow through the radiator.



Today it's 96 degrees and I drove it around town in traffic with the temps hovering between 180 and 190 only because I was running errands. After each restart the temps were high, above 210 like we are used to with heat soak but driving it for a minute or so the temps would go right back to 180 0r 185. Temp monitoring done with a scan tool.



I believe the cause for many of us who opted for "high performance" parts and were left scratching our heads are those very parts. Either the design of the water pump forces too much fluid through the heater, the thermostat outlet to the radiator is too large now or the three row radiator has too much resistance to flow.


In any case my overheating is solved. I hope this helps someone if not more. This theory can be tested on your rig with a simple valve in the closed position. Also, when I re open the valve it goes right back to overheating. The major clue was, in desperation I turned on the heat to max and my temps were fine after that. I wondered how could it be that my heater core was better at cooling than my friggin radiator?



Thanks for reading,

NXJ4CB
Reply With Quote
  #2  
Old July 15th, 2019, 17:40
Anak's Avatar
Anak Anak is offline
Stranger
 
Join Date: Sep 2013
Location: In a strange land
Posts: 3,344
Re: Overheating solved

Interesting.

My XJ has never had trouble with overheating, and I have retained the heater valve which I believe keeps the coolant from going through the heater core. I know conventional wisdom says that valve is unnecessary and just another potential failure point. Your experience says otherwise.

Thank you for posting this up.
__________________
Project "Scope Creep": 1996 4wd 4.0L, AX15
....

Baby it's cold outside.
Reply With Quote
  #3  
Old July 15th, 2019, 18:49
trippled trippled is offline
NAXJA Member
 
Join Date: Apr 2006
Location: colorado springs, co
Posts: 2,304
Re: Overheating solved

Interesting. A lot of the 2000 era Ford trucks have a restrictor in the heater hose, I wonder if something like that would produce a similar result. Thanks for posting this.
Reply With Quote
  #4  
Old July 15th, 2019, 19:54
ehall's Avatar
ehall ehall is offline
NAXJA Member
 
Join Date: Dec 2007
Location: Southern Maryland
Posts: 9,304
Re: Overheating solved

Interesting theory for the later models. I still run a heater core valve on my 91, and temps drop when I open it up (the heater core becomes a second miniature radiator).
__________________
.
my '91 beater rebuild
Reply With Quote
  #5  
Old July 15th, 2019, 19:55
NXJ4CB's Avatar
NXJ4CB NXJ4CB is offline
NAXJA Forum User
 
Join Date: Oct 2007
Location: San Diego
Posts: 12
Re: Overheating solved

Hello,


I am looking for a permanent solution and so far I've found those Ford restrictors, (Dormans description says its variable, which is another whole thing to consider) various hardware store plumbing fitting and also considering a machined rod with a hole drilled. As of now it's 1/4 turn valve from a hardware store doing the job.


I still need to run tests to determine the maximum valve opening/cooling performance. This whole thing was backwards logic until I actually witnessed it myself.



My coworkers not even a Jeep guy and I have yet to go back and say "you were right", I can only imagine the beer he'll think he's owed! It would really please me to see others resolve their cooling issues too. The pattern I've noticed across the forums regarding this overheating is "stock parts" guys say, no problems here and the "high-flow" guys are still beating their heads against the wall.



Cheers,
NXJ4CB
Reply With Quote
  #6  
Old July 15th, 2019, 19:58
NXJ4CB's Avatar
NXJ4CB NXJ4CB is offline
NAXJA Forum User
 
Join Date: Oct 2007
Location: San Diego
Posts: 12
Re: Overheating solved

Hello again,


I feel I really need to stress that I completely bypassed the flow to the heater core. Its totally shut off forcing all the fluid to the radiator and now the radiator is actually doing its job when before it was only getting minimal flow.


Thanks again,
NXJ4CB
Reply With Quote
  #7  
Old July 15th, 2019, 20:25
Patrick S.'s Avatar
Patrick S. Patrick S. is offline
NAXJA Forum User
 
Join Date: Jun 2005
Location: .
Posts: 50
Re: Overheating solved

Hi,


1. My 93 XJ has a heater valve that I believe does not let the water to go thru the heater unless you turn the heat on (moves a flap with vacuum hose). Don't the later XJ's have that?

2. Do you have more info on what model pusher fan you used or a picture of the install? Did it improve cooling some?

Thanks,

Patrick
Reply With Quote
  #8  
Old July 15th, 2019, 21:18
NXJ4CB's Avatar
NXJ4CB NXJ4CB is offline
NAXJA Forum User
 
Join Date: Oct 2007
Location: San Diego
Posts: 12
Re: Overheating solved

Patrick,


I don't know how to add pics but here is the fan info:
Spal 30101505 12" Medium Profile Fan (Push)

It's a tight fit, you won't need any fasteners. I just used some RTV to keep it from slipping out. The core support presses on it enough to hold it place. Also, you will sound like a jet on the taxi way. I get weird looks now when its on, its LOUD. Also, no cutting either! I wired it to run automatically with the main AUX fan and I have a switch to turn it on myself if needed. I fed the fan power from the existing AUX fan relay and the switch controls it by using the wiring in the AC that the computer looks for a ground on that commands the fan on. I took a pic and will post it if figure it out.



My model year doesn't have a stock valve. I read that the fluid flow balancing is accomplished by the diameter of the hoses and ports in the cooling system of my year. That's one more reason I think its those High Flow parts. Changing the diameters of the outlet ports affects the fluid resistance to the point of just recirculating fluid through my heater core and not cooling unless I ran the cabin fan. All the while my radiator was just trickling flow.



NXJ4CB

Reply With Quote
  #9  
Old July 15th, 2019, 21:26
NXJ4CB's Avatar
NXJ4CB NXJ4CB is offline
NAXJA Forum User
 
Join Date: Oct 2007
Location: San Diego
Posts: 12
Re: Overheating solved

Patrick,


To answer your other question, it made no difference on the cooling when overheating. Running my cabin fan was more effective. This is the first full day not overheating in about 8 years. I'm sure it helps but probably not worth the effort. It move alot of air. It will suck my shirt into it when I'm standing near it.


NXJ4CB
Reply With Quote
  #10  
Old July 15th, 2019, 21:58
RCP Phx RCP Phx is offline
NAXJA Forum User
 
Join Date: Mar 2003
Location: Phoenix,Az
Posts: 12,900
Re: Overheating solved

Or you just never fixed it! I own 2 2k's, one I bought brand new and never had any cooling issues for 16yrs.
Reply With Quote
  #11  
Old July 16th, 2019, 05:09
Tim_MN's Avatar
Tim_MN Tim_MN is offline
Freakish Hand Strength
 
Join Date: Mar 2003
Location: Minneapolis, MN
Posts: 6,788
Re: Overheating solved

The Wisdom of the Internet tells me that you can have too much coolant flow and still suffer from overheating. The story goes that the coolant does not dwell long enough in the radiator to fully transfer all the heat it contains.

Like I said, I read it on the Internet, so it must be true.

My 2000 only runs on the warm side when on 4x4 trails deep in the woods on +90 days.
__________________
.
.

Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
Reply With Quote
  #12  
Old July 16th, 2019, 06:01
ehall's Avatar
ehall ehall is offline
NAXJA Member
 
Join Date: Dec 2007
Location: Southern Maryland
Posts: 9,304
Re: Overheating solved

You can test with a set of vice grips on the heater hose too.

Your engine needs a thermostat bypass though. Really. The head gets hot enough to flash boil coolant. You need to have coolant constantly flowing through the head. Really.

Choke it down with a smaller hose or insert if you think the heater hose is flowing too much but you don't want to permanently close it.
__________________
.
my '91 beater rebuild
Reply With Quote
  #13  
Old July 16th, 2019, 11:09
FlyNNN's Avatar
FlyNNN FlyNNN is offline
NAXJA Forum User
 
Join Date: May 2012
Location: Edmonton, Alberta
Posts: 203
Re: Overheating solved

Yikes! Now what about all those threads stating that removing the heater bypass valve is the thing to do with no consequences? Glad I keep mine in.
Reply With Quote
  #14  
Old July 16th, 2019, 12:40
NXJ4CB's Avatar
NXJ4CB NXJ4CB is offline
NAXJA Forum User
 
Join Date: Oct 2007
Location: San Diego
Posts: 12
Re: Overheating solved

Hello again,


I think this theory might only apply to those who have installed (non-stock) high flow thermostat housings, high flow pumps and maybe aftermarket radiators in that order.



The reason I have my setup is one day shortly after lifting my jeep I saw a high temp to me of 215 or so. Before that, the needle never budged. Ever. I thought it was time to squash that, so I put in all the "upgrade" parts I could find all at the same time and was really upset when it started to run even hotter after that.



I assumed that any upgraded part was better as they are advertised to be. For years I could not wrap my head around the possibility that it was those very parts causing the higher temps. Multiple troubleshooting replacements of the same upgraded parts produced the same results. Here's a short list:
3 high flow pumps, 1st Hesco= failed, 2nd=Flowkooler failed, all leaks.

2 CSF 3 row radiators, none failed.

Multiple thermostats, including Robert Shaw, various temps.

Engine rebuilt, head verified good, but it's the 0331.
2 high flow thermostat housings.
1 aftermarket stock aux fan, they're terrible. I replaced that with the Mopar fan, they work better.
Added that Spal fan with no change.


I've been chewing on this all night and I think its those high flow parts creating an environment where most of the flow is just recirculating through heater core and not moving fluid through the radiator much. There are two parallel paths of flow and the design changes of the thermostat housing and or the waterpump create these problems, diverting too much flow through the heater not being cooled at all unless the cabin fan is running.



It's a simple test to perform even with hose clamp pliers like Ehall said in one reply. Here is a link to a hose restrictor and the description deals directly with this theory:
https://jagsthatrun.com/products/hea...ictor-splicers


I'm driving my commute today and will update this thread as I test and verify solutions that I try and report running temps as well.


NXJ4CB
Reply With Quote
  #15  
Old July 16th, 2019, 14:42
RCP Phx RCP Phx is offline
NAXJA Forum User
 
Join Date: Mar 2003
Location: Phoenix,Az
Posts: 12,900
Re: Overheating solved

Quote:
Originally Posted by RCP Phx View Post
Or you just never fixed it! I own 2 2k's, one I bought brand new and never had any cooling issues for 16yrs.
I should mention, I've been here for 56yrs and this week it's been 114* and I have a hi-end stroker that put out heat but my temps run 210* straight up.
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
overheating at freeway speeds issue still not solved!!! AZRockRunner Arizona Chapter 41 June 17th, 2007 01:18
'91 XJ HO NO SPARK SOLVED TXRIVERRAT OEM Tech Discussion 19 December 18th, 2006 21:15
Solved Overheating Problem BigReady Modified Tech Discussion 0 August 11th, 2005 11:56
Overheating is not solved robs Modified Tech Discussion 64 July 3rd, 2005 17:02
I think I solved my overheating issue! GottaBeJeep Modified Tech Discussion 7 June 14th, 2005 19:33


All times are GMT -7. The time now is 23:59.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014