Heater Core Bypass - JeepForum.com
 4Likes
Reply
 
LinkBack Thread Tools
post #1 of 37 Old 07-16-2021, 09:56 AM Thread Starter
jhawkins002
Registered User
2004 WJ 
 
Join Date: Oct 2017
Posts: 25
Garage
Heater Core Bypass

My new-to-me 2004 WJ has a nifty mod that I have really come to appreciate in the sweltering Alabama summer heat. For summer running, the p.o. looped the coolant lines in the engine bay that would normally feed the heater core - which takes a ton of weight off the shoulders of the AC in the cabin. I rarely have to move my fan past the slowest setting to cool the vehicle, which is a HUGE upgrade over the previous WJ I owned! Now to my question for y'all...

The mod currently is about as basic as it can get. Come winter, I'll have to remove the loop and tie the lines back to the heater core under dash. I have an idea to try adding a switchable bypass, and somehow tie it in to the climate settings in-cab. I have been looking at switchable heater line bypasses - and they exist in various forms (electronic, cable-actuated, vacuum, etc). My first thought is to try a vacuum actuated one and attempt linking it in to the various vacuum controls that already adjust various heat-related stuff (blend doors, etc.). Another option would be to get an electronic-controlled one, and attempt something similar - but tying the bypass into the electronic temperature switch somehow seems like it would be much more difficult.

Btw - I know I could do something much simpler and cheaper, like just have a hard cut-off under hood BUT I would like to A) always preserve circulation of coolant and B) automate the bypass so it is tied to the heater controls themselves so that no seasonal re-jiggering is necessary. Just seemed like an interesting project. Push comes to shove I can always leave the system as-is! 😎

jhawkins002 is online now  
Sponsored Links
Advertisement
 
post #2 of 37 Old 07-16-2021, 02:07 PM
cDee63
Web Wheeler
 
cDee63's Avatar
2004 WJ 
 
Join Date: Mar 2018
Location: The Motor City
Posts: 1,505
Garage
I have a valve on mine I can open and close easily. Having it closed had no effect on cooling as far as I can tell, this is the third summer with it. I have to be able to open occasionally, like today. It is hot and muggy AND raining a lot. With the humidity so high the inside windows fog hard with the AC making the inside of the windows cold. Anyone who wears glasses coming in the warm from the cold knows this well. On days like this I have to open the valve to allow the defrost to work.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
1974 Ironhead Sportster, total custom
High speed, low drag
cDee63 is online now  
post #3 of 37 Old 07-16-2021, 08:14 PM
Golden-Arm
Registered User
 
Golden-Arm's Avatar
 
Join Date: Apr 2020
Location: TREASURE COAST
Posts: 938
Garage
i would question why the po looped it. my only guess would be, the heater core is leaking. if it doesn't, do what cdee mentioned. we add a 90 degree ball valve into the heater hose. it uses 3/4" nipples. close it when you don't want heat, open it when you do. install takes 2 minutes.
Attached Thumbnails
DSCN1269.jpg  
anotherheep likes this.

Uphill Slow, Downhill Fast, Tonnage First, Safety Last!
Golden-Arm is offline  
 
post #4 of 37 Old 07-16-2021, 08:33 PM
rabidpenguin
Registered User
2004 WJ 
 
Join Date: Aug 2016
Location: OKC
Posts: 398
Garage
Quote:
Originally Posted by Golden-Arm View Post
i would question why the po looped it. my only guess would be, the heater core is leaking. if it doesn't, do what cdee mentioned. we add a 90 degree ball valve into the heater hose. it uses 3/4" nipples. close it when you don't want heat, open it when you do. install takes 2 minutes.
i’d run some CLR in the core and see what comes out.

to op: there’s a reason it got looped. id start there first honestly. it’s probably a leaky core so i’d get ready to pull the dash to swap it.

2004 WJ,242tcase,255/75/17 Wranglers,UnidenCB w/4ft firestick. Member of RDJ
rabidpenguin is offline  
post #5 of 37 Old 07-17-2021, 07:16 AM
cDee63
Web Wheeler
 
cDee63's Avatar
2004 WJ 
 
Join Date: Mar 2018
Location: The Motor City
Posts: 1,505
Garage
Quote:
Originally Posted by Golden-Arm View Post
i would question why the po looped it. my only guess would be, the heater core is leaking. if it doesn't, do what cdee mentioned. we add a 90 degree ball valve into the heater hose. it uses 3/4" nipples. close it when you don't want heat, open it when you do. install takes 2 minutes.
Here is mine on a 4.7, as one can see it is open. Needed the defrost for the last couple days, super rainy and muggy. I would have put a red handle one being it is hot but ACE was sold out, so blue it is...
Attached Thumbnails
20210717_084916.jpg  
anotherheep likes this.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
1974 Ironhead Sportster, total custom
High speed, low drag
cDee63 is online now  
post #6 of 37 Old 07-18-2021, 07:15 AM
zephyr424
Registered User
1930 CJ2 
 
Join Date: Nov 2016
Location: Albrightsville
Posts: 244
Quote:
Originally Posted by cDee63 View Post
I have a valve on mine I can open and close easily. Having it closed had no effect on cooling as far as I can tell, this is the third summer with it. I have to be able to open occasionally, like today. It is hot and muggy AND raining a lot. With the humidity so high the inside windows fog hard with the AC making the inside of the windows cold. Anyone who wears glasses coming in the warm from the cold knows this well. On days like this I have to open the valve to allow the defrost to work.
I was thinking about doing this, but if it had no effect on cooling, then why install the mod?
zephyr424 is offline  
post #7 of 37 Old 07-18-2021, 08:37 AM
cDee63
Web Wheeler
 
cDee63's Avatar
2004 WJ 
 
Join Date: Mar 2018
Location: The Motor City
Posts: 1,505
Garage
The mod has nothing to do with cooling. It is to shut off the coolant flow through the heater core, keeping 200-210 degree coolant out of the HVAC box in the summer helps keep the interior cooler.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
1974 Ironhead Sportster, total custom
High speed, low drag
cDee63 is online now  
post #8 of 37 Old 07-18-2021, 09:15 AM
JoMc67
Registered User
1999 WJ 
 
Join Date: Aug 2019
Posts: 223
Garage
Basically, keeping Hot Water from flowing behind your Dash (or HVAC) is a plus as it keeps duck work cooler, which in turn helps keep the Cabin feel a little cooler.
JoMc67 is offline  
post #9 of 37 Old 07-18-2021, 10:13 AM
HarryH3
Registered User
2001 WJ 
 
Join Date: Jul 2015
Location: Planet Houston
Posts: 2,835
Quote:
Originally Posted by zephyr424 View Post
I was thinking about doing this, but if it had no effect on cooling, then why install the mod?
I think that you may be confusing the two possible meanings of "cooling" in this thread. @cDee63 is saying that it has no adverse effect on engine cooling. It can have a huge effect on how well the HVAC cooling performs. The more your blend door seal leaks inside the HVAC box, the bigger difference you will notice in the air temp that your a/c can provide.
HarryH3 is offline  
post #10 of 37 Old 07-18-2021, 11:57 AM
zephyr424
Registered User
1930 CJ2 
 
Join Date: Nov 2016
Location: Albrightsville
Posts: 244
Quote:
Originally Posted by HarryH3 View Post
I think that you may be confusing the two possible meanings of "cooling" in this thread. @cDee63 is saying that it has no adverse effect on engine cooling. It can have a huge effect on how well the HVAC cooling performs. The more your blend door seal leaks inside the HVAC box, the bigger difference you will notice in the air temp that your a/c can provide.
Gotcha. Thanks! I ordered two red handled valves from Amazon. One is for the 4.0 and one for the 4.7
zephyr424 is offline  
post #11 of 37 Old 07-18-2021, 02:27 PM
cDee63
Web Wheeler
 
cDee63's Avatar
2004 WJ 
 
Join Date: Mar 2018
Location: The Motor City
Posts: 1,505
Garage
Quote:
Originally Posted by HarryH3 View Post
I think that you may be confusing the two possible meanings of "cooling" in this thread. @cDee63 is saying that it has no adverse effect on engine cooling. It can have a huge effect on how well the HVAC cooling performs. The more your blend door seal leaks inside the HVAC box, the bigger difference you will notice in the air temp that your a/c can provide.
Thank you, I should have been more clear on exactly what cooling I was referring too. It helps, however I have to bite the bullet and do the blend doors/HVAC door seal trick on mine. In winter I have as much hot air coming through the gaps around the radio as I do the actual outlets...

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
1974 Ironhead Sportster, total custom
High speed, low drag
cDee63 is online now  
post #12 of 37 Old 07-18-2021, 04:22 PM
anotherheep
Registered User
 
Join Date: Jun 2020
Posts: 207
Hey , you two with the shut-off valve, that's a great idea. I'm all over that. I haven't had a chance to hook my A/C back up yet and notice the extra heat coming in. Didn't even think that's what it was, but makes sense
anotherheep is offline  
post #13 of 37 Old 07-18-2021, 04:43 PM
cDee63
Web Wheeler
 
cDee63's Avatar
2004 WJ 
 
Join Date: Mar 2018
Location: The Motor City
Posts: 1,505
Garage
Most older cars did just this to control heat. The real old ones like I learned on had an actual rod encased in a housing to control a valve under hood mounted to one of the heater core hoses. I think they did away with it to avoid stagnant coolant in the core in warmer climates where it might not be used very often causing corrosion failures.
anotherheep likes this.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
1974 Ironhead Sportster, total custom
High speed, low drag
cDee63 is online now  
post #14 of 37 Old 07-20-2021, 03:46 PM Thread Starter
jhawkins002
Registered User
2004 WJ 
 
Join Date: Oct 2017
Posts: 25
Garage
Quote:
Originally Posted by Golden-Arm View Post
i would question why the po looped it. my only guess would be, the heater core is leaking. if it doesn't, do what cdee mentioned. we add a 90 degree ball valve into the heater hose. it uses 3/4" nipples. close it when you don't want heat, open it when you do. install takes 2 minutes.
The po specifically said he looped it for summer running, and offered to hook the core back up for the sale. The loop is also set with thumb-twist clamps to make the conversion relatively straightforward. Its clear this is a common mod he did (adding/removing the loop), so I really doubt it was to work around a dead core. That said - I have not actually removed the loop to test the core so I could totally be proven wrong come this winter haha!
jhawkins002 is online now  
post #15 of 37 Old 07-20-2021, 03:58 PM Thread Starter
jhawkins002
Registered User
2004 WJ 
 
Join Date: Oct 2017
Posts: 25
Garage
Thanks to all the suggestions! I was aware I could just put in a cut-off and call it a day 👍 My interest is in installing something that keeps the coolant flowing through a looped bypass instead of plugging the connection as a cut-off would do. Might be totally irrelevant for our Jeeps but there's discussion on other vehicle forums that bypassing the heater core via loop is better than completely plugging the flow for various reasons. Given that there are many solutions for having a looped bypass valve thats either electronic or vacuum actuated, it just seemed logical to try and patch it into the HVAC control system somehow.
jhawkins002 is online now  
Reply

Quick Reply
Message:
Options

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:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











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



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