poor heat from heater core - JeepForum.com
LinkBack Thread Tools
post #1 of 6 Old 09-07-2008, 07:56 PM Thread Starter
Registered User
1998 TJ Wrangler 
Join Date: Apr 2008
Location: Michigan
Posts: 89
poor heat from heater core

I have 2 problems here that i cannot figure out. 1st problem is my heater core. Even when my 98 TJ is warmed up i get warm not hot air if im lucky. I have had the heater core flushed once and that seemed to fix the problem for about a day. What do you guys recommend? Flush it again? replace heater core? 2nd problem has to do with my air vents. If the AC or heat is on any speed other than low...when i accelerate, sometimes the air will switch and only escape through the defrost vent by the windshield on top of the dash. All advice is greatly appreciated.

marko686 is offline  
Sponsored Links
post #2 of 6 Old 09-07-2008, 08:01 PM
Registered User
1998 TJ Wrangler 
Join Date: Sep 2008
Location: Greenfield,IN
Posts: 6
I have a 98 TJ and a 98 YJ. I had the same problems with both. Reverse flush heater core. disconnect both hoses from the engine and flush backwards with the garden hose!! You need PRESSURE!! Another way is to revers the hoses, which will work, with the addition of spline adaptors, but you will need to run the heator for several days to heat it up and flush it out good. Then once it is free and flowing, flush entire system and replace with clean water and antifreeze!!
Jeepdude98 is offline  
post #3 of 6 Old 09-15-2008, 09:18 AM Thread Starter
Registered User
1998 TJ Wrangler 
Join Date: Apr 2008
Location: Michigan
Posts: 89
thanks for the advice...i am going to try that this weekend. Did you have the same problem with the blower...That when accelerating the vents will switch from head, feet, to the defrost only?
marko686 is offline  
post #4 of 6 Old 09-15-2008, 09:24 AM
Jerry Bransford
Jerry Bransford's Avatar
2004 TJ Wrangler 
Join Date: Jan 2003
Location: Escondido, California
Posts: 69,041
Your engine produces less vacuum when you accelerate, and it is vacuum that controls much of your HVAC system. So it sounds like you have a vacuum leak since there's not enough vacuum to keep the HVAC working during acceleration. I'd look for a disconnected, split, or broken vacuum hose, or perhaps a broken vacuum manifold (a fancy word for something that distributes vacuum from one hose to several others).

When you have a choice, buy American made.
Jerry Bransford is offline  
post #5 of 6 Old 09-15-2008, 10:11 AM
Registered User
Tim's Avatar
1997 TJ Wrangler 
Join Date: Mar 2003
Location: Longview Wa
Posts: 946
one test the service manual suggests for your water pump is to turn on your heater.
it may be a sign of something else but lack of heat also points to failing water pump.

not saying yours is kaput, but it is a good thing to know if the signs are present.

97 TJ 4.0, AW-4, Clayton, A.R.B., Highly polished HP30, Super 88
There are no shortcuts to any place worth going
91 XJ 4.7
Tim is offline  
post #6 of 6 Old 09-20-2008, 10:19 PM Thread Starter
Registered User
1998 TJ Wrangler 
Join Date: Apr 2008
Location: Michigan
Posts: 89
I just flushed my heater and that solved the problem! thanx for all the advice and suggestions
marko686 is offline  

Quick Reply

Register Now

In order to be able to post messages on the JeepForum.com 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 e-mail 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.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
new heater core and no heat schlik TJ Wrangler Technical Forum 18 02-12-2010 11:32 AM
No HEAT in TJ, even after flusing heater core upalms TJ Wrangler Technical Forum 16 01-03-2010 10:23 AM
Clogged heater core? Low heat? Here is my fix. igotdoo TJ Wrangler Technical Forum 2 12-29-2009 04:05 PM
no heat...heater core maybe? 94 Sahara YJ Wrangler Technical Forum 9 10-24-2005 06:52 AM

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 On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome