'04 XJ8 w 111,000 miles.

Three years ago I had Jag replace the entire air mixing unit in the dash due to cold air coming out of the driver's side in winter weather and heat only from the passenger side vents.

It's happening again.

That repair was $1500 parts for the entire air unit + $1000 labor.

Ideas? Suggestions?

THANKS

Norm

 

Heater core is a common problem causing cool drivers side. Replacement is the usual cure although a very few have had luck reverse flushing.

Stu

 

Dang, exactly the same symptoms as mine.
1. I shall have to go down the flush route I suppose.
2. I have heard that someone on here do heater core refurbishments, so will look into that too.
3. I can leave it as it is and close the drivers vents and leave open the passenger vents to get heat.. Texas doesn't have that many cold days.

 

That's what we have to do.

I don't understand why the heater core would affect only the driver's side vents and not the passenger vents. ? ?

THANKS

Norm

 

Be sure to check the aux cooling pump. This is an electric pump under the coolant expansion tank. Try to run in 2nd or 3rd gear or at 3 or 4,000 rpm for a few minutes after it has warned up. If you get more heat you have a aux pump failure. This electric motor is on all the time and wears the brushes out. Can rebuild or similar units are used on VW and meets are used. For some reason the jag ones are more expensive.

 

FWIW, I did a search on this forum on this issue and read a lot of posts and the flush doesn't seem to be very successful much of the time.

Norm

 

Could this pump cause the driver's side to blow arctic cold while the passengers side is basking in Caribbean warmth?

 

Ah, well maybe not the flush route then. I will check the aux pump though just in case, but if this didn't work would it not affect both sides and not just the drivers?

 

Certainly in my case. I understand that the way the air and water are routed, low flow takes the heat out most to the passengers side. Fixing the pump fixed my heart.

 

Check all of the fuses. There are individual relays that control flaps that in turn control the flow of air. Have you also tried turning off the dual mode for climate such that one temperature adjustment controls both sides of the car? If you are in dual mode, can you turn up the heat on the affected side to max and the non-affected side to min and get anything different?

 

I tried Dual Mode, without Dual Mode, and every possible combination of modes and temp settings and all to no avail ... arctic air on the left side, hot air on the right side.

I've got an appointment to take the car in this week. The tech says they'll check out other "stuff" before they dig into the heater core to make sure what it is. The tech says he's skeptical that it's the heater core since in 15 years he hasn't seen that to be a problem. Hmm ... he obviously doesn't read this forum.

 

We wait with baited breath!!

 

What nobody has ever told me, or put on the forum, is what causes the heater matrix to silt-up. Where does the silt come from ? Surely the casting and machine shops don't leave crud in the castings before engine assembly ?

 

precipitation from the coolant as it ages

 

My Jag indie told me it is some kind of mechanical failure in the core itself, a baffle of some kind collapses in the core preventing the flow of coolant to the drivers side. I replaced my core myself and the heat works perfect on both sides. The original core was pretty clean inside, I flushed it and only got a little discolored water out. I threw it out before I talked to my indie about it when I took my jag in for a trans service. In hindsight I would have liked to sectioned it but I was totally fed up with all the work by the time I was done I just wanted to be rid of it.

Stu

 

SO here's the challenge !

Could the next guy who replaces his heater matrix due to blockage, please section it and put a photo on here, please, so we can all see what the problem looks like.

 

UPDATE: Jag dealership called and after some troubleshooting the tech decided that is was the heater core. When I took it in I told them that the forum wisdom pointed to the heater core. Oh well, I paid for some time troubleshooting but that's Ok. The tech was able to test the blend doors on some kind of computer and determined they were working Ok.

Also they said I was consuming a wee bit of oil on startup so recommended a replacement of the PCV and a throttle body service. I could have done that but it's winter here in the North Country and decided to be lazy and let them do it.

About $1300 for the heater core (which probably included some troubleshooting time) + almost $400 for the PCV related issue.

They have to order parts so I should get it back in a few days.

 

Has anyone had the opposite issue, cold air on the passenger side and warm air on the driver? My wife was complaining that the car doesn't get warm enough, and I'm thinking how hot do you want it. I then rode on that side and it is significantly cooler. I left the driver setting at 72 and put the pass side to max 89, and the air never got any warmer and still was much cooler than the driver side.

 

Interesting. It seems like the problem is always on the driver's side but maybe someone will come in here with a story similar to yours.

Our heater matrix fix is suppose to be done tomorrow.

 

It is a mystery to me why the passenger side problem rate should be much different.
As far as I can see the heater core is split---it has separate sections for the passenger side and the driver side.


Each side is fed through a dedicated pipe and valve( the DCCV is actually 2 separate valves).


Each side has a dedicated hose coming from the the DCCV.


There is a common return header on the heater core and a common return hose.


Similarly the air distribution system is split to match the split heater core.


So logically failure of the auxiliary water pump should affect both sides equally


problems with engine thermostat should affect both sides equally.


Failures which could affect just one side ---failure of one side of the DCCV,failure of air distribution doors, either electrical actuators or the connecting arms, and preferential deposts of sludge in one side or the other.


The reason I bring it up is I was in a 2005 Vanden Plas yesterday where the drivers side upper vents were sort of cold,but when air was switched to the drivers footwell it was hot.At the same time the passenger side was uniformly hot.(All with the same temperature setting).