Jeep Running Too Hot - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum

Join Wrangler Forum Today

Thread Tools

Please support our sponsors and let them know you heard about them on
Old 05-31-2010, 07:00 PM   #1
zpratt4's Avatar
Join Date: Sep 2007
Location: Knoxville, TN
Posts: 257
Jeep Running Too Hot

My 1999 TJ keeps overheating. I do not have any leaks in the radiator, and I have already replaced the thermostat. Does anybody know what I should do or look for to find what the problem is? Thanks in advance.

zpratt4 is offline   Quote Quick Reply
Old 05-31-2010, 07:28 PM   #2
Founder, ThumbJeeps

WF Supporting Member
sevenservices's Avatar
Join Date: Sep 2009
Location: Mid-Michigan/Thumb
Posts: 3,952
first things first, check the radiator really good with a flashlight and make sure it did'nt take a rock or anything to stop the flow through it.

Make sure you have the correct thermostat???

May need a flush???

Is it low on coolent?

Are you pulling a boat up hills???

Founder, ThumbJeeps

1994 Wrangler YJ I6 4.0 H/O Auto 3 spd. 4" RC (33x12.5) (15x8) 3:54 Gears
sevenservices is offline   Quote Quick Reply
Old 05-31-2010, 08:56 PM   #3
TJeepman's Avatar
Join Date: May 2010
Location: Nova Scotia
Posts: 676
Check the coolant level in the radiator. Are both radiator hoses hot? Putting the heater on make any difference? Bottom radiator hose in good shape?
- dirty radiator maybe
- worn out water pump/impeller maybe.
2003 Jeep TJ Sport - 4.0L - 251,430 kms
2002 and 2007 Grand Caravans - Sport & SXT
TJeepman is offline   Quote Quick Reply
Old 05-31-2010, 09:05 PM   #4
I am JD & It's my Dream

WF Supporting Member
::WF Administrator::
JDsDream's Avatar
Join Date: Jan 2009
Location: The Peach State
Posts: 27,300
Images: 4
could be a fan clutch.
The kind of woman that when my feet hit the floor each morning the devil says "Oh Crap, She's up!"

To All Of Our Forum Veterans and Active Service Members.
Our Debt To You Is Greater Than We Could Ever Repay.
Thank You

Become a Supporting Member!
JDsDream is offline   Quote Quick Reply
Old 05-31-2010, 09:20 PM   #5
zpratt4's Avatar
Join Date: Sep 2007
Location: Knoxville, TN
Posts: 257
all of the hoses look good. coolant level is good. thermostat is the right one. maybe i'll check to make sure nothing is clogging the radiator. i hope it is not the water pump
zpratt4 is offline   Quote Quick Reply
Old 05-31-2010, 10:32 PM   #6
that's what she said

WF Supporting Member
jgano23's Avatar
Join Date: Oct 2008
Location: \m/-_-\m/
Posts: 16,482
Send a message via AIM to jgano23 Send a message via Yahoo to jgano23
when is it overheating? only while sitting or at low speeds? is it overheating while driving down the highway? (as jd said) did you check the fan to see if the fan clutch isn't working?
jgano23 is offline   Quote Quick Reply
Old 05-31-2010, 11:36 PM   #7
For_4x4's Avatar
Join Date: May 2010
Posts: 61
Is it building pressure? After a drive squeeze the upper radiator hose to feel if the system has pressure in it. If there is no pressure in the system you have a leak, also if there is no pressure this means that the boiling point of the coolant is much lower than if the system was at the normal 18psi. Low pressure and boiling commonly leads to overheating.

A radiator cap can leak and you will never see a drip on the ground they just leak air pressure and a small about of coolant witch will end up in the overflow bottle.

If its building pressure I would then vote clogged radiator or bad fan clutch.
02' TJ Sport, 4.0 I-6, NV3550, D44 rear
2'' Rubicon Express, 32x11.50 Cooper STT
For_4x4 is offline   Quote Quick Reply
Old 06-01-2010, 12:07 AM   #8
zpratt4's Avatar
Join Date: Sep 2007
Location: Knoxville, TN
Posts: 257
while i am idling, it stays around 210 like normal, but when i am on the highway, it starts rising and after a while of running it at about 55-65 mph it goes into the red and the check gauges light comes on.
zpratt4 is offline   Quote Quick Reply
Old 06-01-2010, 12:15 AM   #9
Knows a couple things...

WF Supporting Member
Jerry Bransford's Avatar
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 33,749
Images: 2
Drop the coolant level down enough via the drain valve on the bottom of the radiator so you can see the top of the radiator core underneath the radiator cap. With a flashlight, look for telltale calcium deposits around the cooling channel openings indicating the radiator is becoming clogged with hard water deposits.

If you see mineral buildup inside, such deposits are caused by using tap water in the radiator instead of the required distilled water which is mineral free. At this point, I would suspect the radiator is getting clogged with those hardwater deposits. And while most radiators can be "rodded out" to get rid of such deposits, the TJ's radiator cannot be. Once it gets to that point, it can only be replaced because once it is taken apart to rod it out, it cannot be effectively resealed again since it is crimped together, not soldered.

When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply

Quick Reply

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools

Posting Rules
You may post new threads
You may 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Biggest Jeep Freek Contest!!!! txoutdoorx4 Classifieds Archive 6 02-21-2011 11:48 AM
So jeep was running fine till!!!! bck4more YJ General Discussion Forum 2 05-22-2010 07:01 PM
My jeep is running hot 89YJislander YJ General Discussion Forum 10 09-18-2009 11:03 PM
NEW Aussie Locker For Dana 30 Jeep Differentials (IL) BUSAFREAK Classifieds Archive 13 01-22-2008 10:39 PM
Got my Jeep running about a week ago... The Sos YJ General Discussion Forum 2 11-08-2007 12:38 AM

Download our Mobile App

» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 02:46 AM.

Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC. is not in any way associated with the Chrysler Motors LLC