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 August 11th, 2017, 14:31
Tony the Liger Tony the Liger is offline
NAXJA Forum User
 
Join Date: Aug 2017
Location: USA
Posts: 38
Temperature jumping from warm to hot and back again

Just completed the following on my new-to-me '00 XJ: replaced the valve cover gasket, a pinion seal, steering stabilizer shock, two axle U-joints, one wheel cylinder, and one set of brake shoes. On my way home from the garage, the XJ started to overheat a bit.

This is the first time it has overheated on me. I've only had it a few weeks and haven't driven it much, but I bought it in a town that's around three hours away from me, so I drove it around town and on the interstate for well over three consecutive hours on the day I bought it and didn't experience any overheating whatsoever. After warming up today, the temp sat just a hair past 210, then gradually climbed to the first notch past 210. I made it home by that point and parked it for a couple hours. After letting it sit, I took it up the road and back, and in that time the temp climbed to the same point, sat for a few minutes, then out of nowhere it spiked to the notch below 260. It sat there for a few second, then dropped back to just above 210. Sat for a few more seconds, then did it all over again.

Hoping the thermostat's sticking and I can get by with a $12 or so fix. Any thoughts?
Reply With Quote
  #2  
Old August 11th, 2017, 15:05
Tbone289's Avatar
Tbone289 Tbone289 is offline
NAXJA Forum User
 
Join Date: Oct 2009
Location: Missouri
Posts: 102
Re: Temperature jumping from warm to hot and back again

Check operation of both fans. You should easily hear the main fan after the clutch has engaged at full operating temp (around 210). When you pull away from a stop, you should hear it over the sound of the engine. Your aux (electric) fan should turn on once 223 degrees is reached.

Were you driving around when this happend, or was the Jeep sitting and idling? If the cooling system is working properly, you really should never get over 210 while driving around, but it will creep up while idling.

Your description of the problem is not indicative of a sticking thermostat...
Reply With Quote
  #3  
Old August 11th, 2017, 15:14
Tim_MN's Avatar
Tim_MN Tim_MN is online now
Freakish Hand Strength
 
Join Date: Mar 2003
Location: Minneapolis, MN
Posts: 5,886
Re: Temperature jumping from warm to hot and back again

Replace the radiator cap. Buy a premium Stant or genuine Jeep radiator cap. The symptoms described are what happens when the stock 16lbs radiator cap starts to fail. The cap cannot hold the normal cooling system pressure and the pressure loss allows the boiling point of the coolant to drop, and the coolant momentarily flashes to steam. As the steam bubble passes the Coolant Temp Sensor the gauge jumps to 260. When normal or near normal cooling system pressure returns, the steam no longer forms.
__________________
.
.

Quote:
Originally Posted by bimmerjeeper

Blanket caught in the rear liftgate latch. Now I can't open.
.
Reply With Quote
  #4  
Old August 11th, 2017, 17:59
Tony the Liger Tony the Liger is offline
NAXJA Forum User
 
Join Date: Aug 2017
Location: USA
Posts: 38
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by Tbone289 View Post
Check operation of both fans. You should easily hear the main fan after the clutch has engaged at full operating temp (around 210). When you pull away from a stop, you should hear it over the sound of the engine. Your aux (electric) fan should turn on once 223 degrees is reached.

Were you driving around when this happend, or was the Jeep sitting and idling? If the cooling system is working properly, you really should never get over 210 while driving around, but it will creep up while idling.

Your description of the problem is not indicative of a sticking thermostat...
I'll double check, but I'm almost positive both fans are working. The problem occurred while I was driving. When it happened the first time, I got home, parked, and let it idle for a few minutes. It stayed at the notch above 210 the entire time.
Reply With Quote
  #5  
Old August 11th, 2017, 18:01
Tony the Liger Tony the Liger is offline
NAXJA Forum User
 
Join Date: Aug 2017
Location: USA
Posts: 38
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by Tim_MN View Post
Replace the radiator cap. Buy a premium Stant or genuine Jeep radiator cap. The symptoms described are what happens when the stock 16lbs radiator cap starts to fail. The cap cannot hold the normal cooling system pressure and the pressure loss allows the boiling point of the coolant to drop, and the coolant momentarily flashes to steam. As the steam bubble passes the Coolant Temp Sensor the gauge jumps to 260. When normal or near normal cooling system pressure returns, the steam no longer forms.
I'll give it a shot. Makes sense. I appreciate the info.

Just got home with a new thermostat. You guys recommend taking it back, or go ahead and change it?
Reply With Quote
  #6  
Old August 11th, 2017, 20:02
ehall's Avatar
ehall ehall is offline
NAXJA Member
 
Join Date: Dec 2007
Location: Southern Maryland
Posts: 8,864
Re: Temperature jumping from warm to hot and back again

Get an infrared thermometer to check the thermostat housing. The gauge setup isn't the most reliable.
__________________
.
my '91 beater rebuild
Reply With Quote
  #7  
Old August 11th, 2017, 20:09
Tony the Liger Tony the Liger is offline
NAXJA Forum User
 
Join Date: Aug 2017
Location: USA
Posts: 38
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by ehall View Post
Get an infrared thermometer to check the thermostat housing. The gauge setup isn't the most reliable.
Not sure if this affects your (or anyone else's) prognosis, but there was steam coming from the engine. I don't think it was an inaccuracy in the gauge.

Last edited by Tony the Liger; August 11th, 2017 at 20:49.
Reply With Quote
  #8  
Old August 11th, 2017, 21:40
Slimer Slimer is offline
NAXJA Forum User
 
Join Date: Jun 2017
Location: Tempe, AZ
Posts: 81
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by Tony the Liger View Post
Just completed the following on my new-to-me '00 XJ: replaced the valve cover gasket, a pinion seal, steering stabilizer shock, two axle U-joints, one wheel cylinder, and one set of brake shoes. On my way home from the garage, the XJ started to overheat a bit.

This is the first time it has overheated on me. I've only had it a few weeks and haven't driven it much, but I bought it in a town that's around three hours away from me, so I drove it around town and on the interstate for well over three consecutive hours on the day I bought it and didn't experience any overheating whatsoever. After warming up today, the temp sat just a hair past 210, then gradually climbed to the first notch past 210. I made it home by that point and parked it for a couple hours. After letting it sit, I took it up the road and back, and in that time the temp climbed to the same point, sat for a few minutes, then out of nowhere it spiked to the notch below 260. It sat there for a few second, then dropped back to just above 210. Sat for a few more seconds, then did it all over again.

Hoping the thermostat's sticking and I can get by with a $12 or so fix. Any thoughts?
After extensive testing with my overheating XJ, this is pretty standard. If you look at my thread on the very same issue you can see the video I posted.

What is happening is that the stock gauge in the dash is not very accurate. Your engine is probably actually running about 240 all the time like mine is. When it finally hits 260 the check engine light comes on and the gauge shoots up almost simultaneously. When the thermostat then opens and pushes the cool coolant from the radiator back into the block it is just enough to send the gauge back down out of the red. My gauge basically doesn't read anywhere in the upper 2/3's of the gauge. It runs just to the right of center and then shoots over to just below the max temperature.

I finally figured this all out by doing what RCP Phx told me. He said to order a cheap meat thermometer off of Amazon with dual inputs. The inputs are very thin and can easily fit in the hoses with the wiring leading out under the clamps back to my interior. I put the probes in every hose that I could and drove around and checked out the temps. My Jeep runs hot no matter what I do.

I just orderd the fancy Hesco Water Pump and the Griffon Radiator. Hopefully that solves my issues. I have replaced everything else.
Reply With Quote
  #9  
Old August 12th, 2017, 07:58
Tim_MN's Avatar
Tim_MN Tim_MN is online now
Freakish Hand Strength
 
Join Date: Mar 2003
Location: Minneapolis, MN
Posts: 5,886
Re: Temperature jumping from warm to hot and back again

Steam would indicate a coolant leak ?? Leakage would allow loss of system pressure.

The thermostat and the radiator cap are both routine maintenance items that should replaced every few years, and as a bonus they are inexpensive. Be sure to buy genuine Jeep replacement parts, or the best quality parts the store has. Cheap parts are cheap for a reason. Another thing to look for is leaky frost plugs on the side of the block and the rear of the cylinder head.

The dashboard temperature gauge is not a certified measuring device, it is more correctly described as an indicator. Normal indication is about 210*. If you drive for a whole year and it indicates in the same location every day, everything is normal and OK. If it shows much hotter than normal, you need to pull over until it cools down, and then do some diagnostics. The PCM does buffer temp gauge readings, and temps will vary more and quicker than the gauge indicates. Part of the PCM programming is also to alert to a impending overheat by flinging the needle all the way to the right and lighting the Check Engine Light.

The stock 195* thermostat, unless defective, is already fully open at about 195*.
__________________
.
.

Quote:
Originally Posted by bimmerjeeper

Blanket caught in the rear liftgate latch. Now I can't open.
.

Last edited by Tim_MN; August 12th, 2017 at 08:07.
Reply With Quote
  #10  
Old August 12th, 2017, 09:57
Tony the Liger Tony the Liger is offline
NAXJA Forum User
 
Join Date: Aug 2017
Location: USA
Posts: 38
Re: Temperature jumping from warm to hot and back again

Thought it might be possible that when removing hoses to changing the valve cover gasket, air might've gotten into the system, messed with the pressure, etc. So, this morning I added coolant via the hose, resulting in short-term good news but possible long-term bad news.

My XJ has definitely leaked coolant at some point. It accepted 1.5 gallons of coolant before it was fully topped off. This remedied the overheating issue for the time being, but I'm left to wonder where that 1.5 gallons of coolant went in the first place. I haven't found any coolant on the ground around the truck since I've owned it, nor can I find any fresh coolant where it shouldn't be in the engine bay.

This being a '00, my fear is that I've got the head crack and coolant is flowing out the exhaust. Going to look into having it pressure tested this week.
Reply With Quote
  #11  
Old August 12th, 2017, 10:06
RCP Phx RCP Phx is offline
NAXJA Forum User
 
Join Date: Mar 2003
Location: Phoenix,Az
Posts: 10,527
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by Tony the Liger View Post
Thought it might be possible that when removing hoses to changing the valve cover gasket, air might've gotten into the system, messed with the pressure, etc. So, this morning I added coolant via the hose, resulting in short-term good news but possible long-term bad news.

My XJ has definitely leaked coolant at some point. It accepted 1.5 gallons of coolant before it was fully topped off. This remedied the overheating issue for the time being, but I'm left to wonder where that 1.5 gallons of coolant went in the first place. I haven't found any coolant on the ground around the truck since I've owned it, nor can I find any fresh coolant where it shouldn't be in the engine bay.

This being a '00, my fear is that I've got the head crack and coolant is flowing out the exhaust. Going to look into having it pressure tested this week.
That's how it all started on my 2k!
Reply With Quote
  #12  
Old August 12th, 2017, 10:13
Tony the Liger Tony the Liger is offline
NAXJA Forum User
 
Join Date: Aug 2017
Location: USA
Posts: 38
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by RCP Phx View Post
That's how it all started on my 2k!
That's a kick to the nuts. I'm guessing you replaced the head?

Did the head crack lead to any other issues that I should expect, or did a replacement fix everything?
Reply With Quote
  #13  
Old August 12th, 2017, 10:54
Slimer Slimer is offline
NAXJA Forum User
 
Join Date: Jun 2017
Location: Tempe, AZ
Posts: 81
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by Tim_MN View Post
Steam would indicate a coolant leak ?? Leakage would allow loss of system pressure.

The thermostat and the radiator cap are both routine maintenance items that should replaced every few years, and as a bonus they are inexpensive. Be sure to buy genuine Jeep replacement parts, or the best quality parts the store has. Cheap parts are cheap for a reason. Another thing to look for is leaky frost plugs on the side of the block and the rear of the cylinder head.

The dashboard temperature gauge is not a certified measuring device, it is more correctly described as an indicator. Normal indication is about 210*. If you drive for a whole year and it indicates in the same location every day, everything is normal and OK. If it shows much hotter than normal, you need to pull over until it cools down, and then do some diagnostics. The PCM does buffer temp gauge readings, and temps will vary more and quicker than the gauge indicates. Part of the PCM programming is also to alert to a impending overheat by flinging the needle all the way to the right and lighting the Check Engine Light.

The stock 195* thermostat, unless defective, is already fully open at about 195*.
Maybe, maybe not. In my case, if the thermostat is already fully open how do you explain the engine cooling off so quickly and the guage returning back to the middle? These are confirmed temperature trends using two real-time probes. Anyhow, I am completely befuddled by my overheating . Hoping that the new Hesco Water Pump and Griffon Radiator fix the problem; otherwise I will have to light the thing on fire.
Reply With Quote
  #14  
Old August 12th, 2017, 11:36
Tony the Liger Tony the Liger is offline
NAXJA Forum User
 
Join Date: Aug 2017
Location: USA
Posts: 38
Re: Temperature jumping from warm to hot and back again

FWIW, I took off the oil cap and looked around as best I could, and I didn't see any greenish tint or obvious cracks.
Reply With Quote
  #15  
Old August 12th, 2017, 11:40
RCP Phx RCP Phx is offline
NAXJA Forum User
 
Join Date: Mar 2003
Location: Phoenix,Az
Posts: 10,527
Re: Temperature jumping from warm to hot and back again

Quote:
Originally Posted by Tony the Liger View Post
That's a kick to the nuts. I'm guessing you replaced the head?

Did the head crack lead to any other issues that I should expect, or did a replacement fix everything?
When I bought a new head last year, it just revealed that other damage had occurred, I got another 6 months out of it before I couldn't stand it any longer and decided a stroker was in order!
http://naxja.org/forum/showthread.php?t=1140839
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
99 xj runs horrible warm pinging stalls hard restart when warm 96xjdennis OEM Tech Discussion 0 January 9th, 2015 05:50
Jumping Back In HossHoffer Colorado Chapter 1 April 16th, 2013 18:42
RPM's jumping around XJSteven OEM Tech Discussion 4 August 1st, 2012 21:14
JUmping the XJ Egodfrey North Atlantic Chapter 16 October 12th, 2011 11:06
Think he was jumping?? mattyj SoCal Chapter 10 July 14th, 2009 21:53


All times are GMT -7. The time now is 18:28.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014