Heat works only on passenger side - Page 2 - JK-Forum.com - The top destination for Jeep JK Wrangler news, rumors, and discussion

Notices
Stock JK Tech Bulletin board forum regarding issues with OE (original equipment) components of the Jeep JK Wrangler (Rubicon, Sahara, Unlimited and X) such as factory suspension parts, engine, transmission, body parts, interior fixtures and the on-board computer.
Sponsored by DV8 Offroad
Click Here

Heat works only on passenger side

 
Old 12-31-2018, 06:29 AM
  #11  
Super Moderator
 
Rednroll's Avatar
 
Join Date: Apr 2010
Location: SE Michigan
Posts: 3,821
Thanked 91 Times in 85 Posts
Default

Originally Posted by sjm2011 View Post
Just dealt with this problem the last few weeks. Daughter bought a 2011 Wrangler that she loves. We had to fix a few things here and there but for the most part has been a good vehicle. Cold weather hit here about 6 weeks ago and she discovered little to no heat out of her driver side vents. I checked coolant levels, thermostat, etc and the only thing we noticed was that the radiator and reservoir seemed to have some gunk. Took the jeep to our local mechanic and he did a thorough coolant flush. Still no heat on the driver's side. I warmed up the jeep to operating temps and hit each one of the heater core hoses with my IR thermometer. Inlet temp was around 180 degrees and oulet was about 90 degrees. Figured the heater core was plugged and would need replaced. I backflushed the heater core with the garden hose. Surprisingly I didn't get much gunk or discolored water and had good flow. As a last gasp effort, I switched the input/output hoses to the heater core. Topped off the radiator and took it for a test drive. Drivers vents had more heat than before but still not 100%. My daughter drove it this way for 2 or 3 days and whatever blockage was in the heater core must have come loose when we reversed the flow direction. She has full heat now to all vents. I realize that whatever was blocking the core is now in the coolant but doing another flush is much easier than changing out the heater core. Fingers crossed that it continues to work.
Based upon your original description of "gunk" being present, I would venture to guess you may have had the Hoat/Oat coolant mixture problem which causes a gel to form. The heater core has the smallest passages throughout the system, so it is likely the gel was blocking the passages in the HC. Reversing the hoses sounds like a good idea. That way you essentially got a reverse flush using hot coolant. However, whatever was in the coolant blocking the HC is now somewhere running through the system.

Rednroll is offline  
Old 12-31-2018, 07:01 AM
  #12  
JK Newbie
 
Join Date: Dec 2018
Location: Chicora PA
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Smile

Originally Posted by Rednroll View Post
Based upon your original description of "gunk" being present, I would venture to guess you may have had the Hoat/Oat coolant mixture problem which causes a gel to form. The heater core has the smallest passages throughout the system, so it is likely the gel was blocking the passages in the HC. Reversing the hoses sounds like a good idea. That way you essentially got a reverse flush using hot coolant. However, whatever was in the coolant blocking the HC is now somewhere running through the system.
The gunk did have a gel look and feel to it and the mechanic commented about how much stuff was cleaned out during the flush. I'll do another coolant flush in a couple months to get rid of any remaining residue. I think that if the clog was the casting sand a lot of the other Wrangler owners have had problems with, my core would have been toast and needed replaced.
sjm2011 is offline  
Old 12-31-2018, 08:21 AM
  #13  
JK Jedi
 
resharp001's Avatar
 
Join Date: Jun 2013
Location: Willow Park, TX
Posts: 4,058
Thanked 193 Times in 188 Posts
Default

I haven't had to research this, so probably a dumb question.....but if the whole heater core is clogged (implied by inlet temp of 180 and outlet only 90), how does heat get to one side of the vehicle? I'd think neither side would be getting hot air?? Again, I've not had to look at the heater core on mine before....am I missing something obvious?
resharp001 is offline  
Old 12-31-2018, 08:36 AM
  #14  
JK Newbie
 
Join Date: Dec 2018
Location: Chicora PA
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Default

I watched some youtube videos of other Wrangler owners with the same symptoms changing out their heater cores. When they cut apart the old cores, the driver's side had the blockage. The inlet/outlet tubes are on the passenger's side so there must be some flow even with the restriction. I'm not sure of the flow pattern thru the core but so far it has helped us get heat into the Wrangler without any extra cost.
sjm2011 is offline  
Old 12-31-2018, 08:39 AM
  #15  
JK Jedi
 
resharp001's Avatar
 
Join Date: Jun 2013
Location: Willow Park, TX
Posts: 4,058
Thanked 193 Times in 188 Posts
Default

ah, thank you.
resharp001 is offline  
Old 01-01-2019, 06:32 AM
  #16  
Super Moderator
 
Rednroll's Avatar
 
Join Date: Apr 2010
Location: SE Michigan
Posts: 3,821
Thanked 91 Times in 85 Posts
Default

Originally Posted by sjm2011 View Post
I watched some youtube videos of other Wrangler owners with the same symptoms changing out their heater cores. When they cut apart the old cores, the driver's side had the blockage. The inlet/outlet tubes are on the passenger's side so there must be some flow even with the restriction. I'm not sure of the flow pattern thru the core but so far it has helped us get heat into the Wrangler without any extra cost.
Yes, mine was blocked with casting sand.
To add to this, here's what I feel is happening. Even with the majority of my HC caked with casting sand the inlet and outlet hoses had the same temp readings which originally made me think my HC was ok. Even with a brand new HC, what I found is that the driver's side vent will always blow cooler than all the other vents. I found it was 15-20deg F cooler once my heat was back to fully working good. The air has to travel furthest from the HC to reach the driver's side vent than any of the other vents and that air also passes over the blend door to get to that vent (there's very cold air directly behind that blend door in the Northern winter areas), so that's my theory on the reason the driver's side vent is always slightly cooler. Just loss of heat of the air due to thermodynamics of distance traveled and flowing over a cold surface (ie the blend door). Anyways, the heater core is about 12inx8in in area. With a partially clogged heater core the area of the HC which is actually getting hot is drastically reduced (think of it as now having a HC which is 3inx8in in actual area) and therefore the driver side vent will still be coolest but since it's 20deg cooler to begin with, it will be the most noticeable where you will feel cold air blowing out of it. Since the HC is not fully blocked when caked with casting sand, coolant will still pass through it and that is the reason the inlet and outlet hoses will measure the same temp as is what I discovered. The problem is that the hot coolant is no longer able to flow through all the slots inside of the heater core to be able to fill the entire HC. In the example above with the gel, it is likely many more of the tubes inside the core were blocked and is the reason for the inlet/outlet hose temp differences. Gel material is just much more easier to back flush out of the HC stuck in those tubes than casting sand which is packed inside of those tubes.

At least that's my theory and I'm sticking to it. I've had others doubt my theory and when I asked them for a better one they couldn't provide one. As many know I've spent a lot of time diagnosing my heater related problems, and I dissected and inspected my clogged heater core once I removed it, so I've grown pretty familiar with how the heater works in our JKs, so I feel pretty confident with my theory until someone provides a better one.

Last edited by Rednroll; 01-01-2019 at 06:35 AM.
Rednroll is offline  
Old 01-01-2019, 08:30 AM
  #17  
Super Moderator
 
Rednroll's Avatar
 
Join Date: Apr 2010
Location: SE Michigan
Posts: 3,821
Thanked 91 Times in 85 Posts
Default

I've never seen an actual JK HVAC diagram, but based upon the work I've done on my heater system and what I'm describing, I put this simplified diagram together to better show what I think is going on. The driver side vent, the hot air travels through the ducts the furthest and also passes over the blend door area on it's way to reach the driver side vent. Combine that with what sjm2011 described of the HC becoming more clogged on the side closest to the driver side and it all adds up to the least amount of heat from the driver side vent. Basic thermo-dyanamics at work if you ask me.

Last edited by Rednroll; 01-01-2019 at 10:04 AM.
Rednroll is offline  
Old 01-02-2019, 05:14 AM
  #18  
JK Jedi
 
resharp001's Avatar
 
Join Date: Jun 2013
Location: Willow Park, TX
Posts: 4,058
Thanked 193 Times in 188 Posts
Default

^^^That makes good bit of sense. Got me curious to run check the temps out of each vent now just to see how much lower my driver's vent is.
resharp001 is offline  
Old 01-02-2019, 02:58 PM
  #19  
Super Moderator
 
Rednroll's Avatar
 
Join Date: Apr 2010
Location: SE Michigan
Posts: 3,821
Thanked 91 Times in 85 Posts
Default

Originally Posted by resharp001 View Post
^^^That makes good bit of sense. Got me curious to run check the temps out of each vent now just to see how much lower my driver's vent is.
That's something I'ld be interested to see. No one seems to ever measure all their vents when the heat is working fine. They just notice the driver's side is the coldest when the heat starts performing poorly.

When I finally got things back to working with my heat, I measured all the vents. Heat was 20deg F lower from the driver's vent than all the others. I'm contributing this due to the air having to travel further and it also blows across that section of the ducts where the blend door is located. The way I measured it previously without a thermometer is that I remembered when it was really cold out I would I hold up my hand directly in front of one of the center vents and I had to pull it away after about 30 seconds because my hand was starting to burn. However, when I did that in front of my driver side vent, I could hold my hand there forever. Thus, proving even when it was new the driver's side vent was cooler than the other vents.

Here's my measurements, with a brand new heater core and a full coolant system which has been burped.
Driver's vent=155.5deg F


Center vent (Driver's side=173.7deg F)


Passenger's vent (Hard to read=172.9deg F) *Harbor freight thermometer screen blanks out at 175 deg F.

Last edited by Rednroll; 01-02-2019 at 03:23 PM.
Rednroll is offline  
Old 01-02-2019, 03:20 PM
  #20  
Super Moderator
 
Rednroll's Avatar
 
Join Date: Apr 2010
Location: SE Michigan
Posts: 3,821
Thanked 91 Times in 85 Posts
Default

And Prior to replacing my heater core here were the comparable measurements.

Driver side vent (bad heater core)


Center vent /Driver Side (bad heater core)


Passenger vent (bad heater core)


So in both instances, of good HC vs bad HC there was a 20 deg F difference between the center vent and the driver side vent. With the bad HC the passenger side vent was about 15 deg lower than with the new HC. I would contribute this to the fact that the HC is more clogged on the driver side, so it's performance is down, but not down as far as the center vent and the driver side vent which would be getting more of the air blowing across the HC section more towards the driver side which has more blockage.

Last edited by Rednroll; 01-02-2019 at 03:29 PM.
Rednroll is offline  

Quick Reply: Heat works only on passenger side


Contact Us About Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: