Hello again, another HVAC question. Just FYI, I did a pretty extensive search, and I'm not seeing exactly my situation, but several close ones. (I'm seeing a lot of X-type HVAC questions.)
Mine is a 2005 VJ8 VDP. I've noticed the passenger vents blow pretty good heat when on. The two middle vents: 1 driver and 1 passenger, I can tell the driver's side is slightly cooler than the passenger side right next to it. Also - the left-most vent (to the left of the steering wheel) is quite cool when on max heat.

I've read about the heater core being plugged, but I'm thinking this is a blend-door issue.

I'm a rookie when it comes to this, so please tell me where to start the diagnosis. Oh also - please tell me this isn't a $2000 dealer repair. Thanks guys.

 

Due to the design of it, a partially blocked heater core is quite common, especially after 6 years, so I would try back flushing it first to see if that cures it.

I had mine changed last year ('04) which fixed my problem but wish I had tried back flushing it first. Some posts said backflushing wouldn't work as the debris in the core solidifies but I have since seen many people who have been successful doing it.

 

the car has dual heater cores, I would guess the driver side is blocked. Try backflushing it.

 

I understand your thought process, but in actuality the Denso Climate system has proven pretty bulletproof. The only 'common' repair really has been the module that controls the blower motor. Once in a while a backflush will help, but I'd be preparing for the heater core.

That's not to say you might not be correct, though.

Good luck!

 

Having paid a lot of money to have mine changed, I can confirm there is only one core, on a 2 zone system anyway.

The pipes enter and exit on the same (short) side, so one of the theories is that the flow is less at the far end so sediment collects there and eventually blocks it.

 

Just a bit of trick I did that worked. I had exactly same symptom - drivers side center vent blows lukewarm air when passenger side is hot.

I pulled the hoses off where they connect to hardpipe to core (sort of a sliding gate quick-disconnect, then with antifreeze still in system, I hooked up a can of Briggs & Stratton Pressure Washer Pump Cleaner to upper ("T") pipe and blew hole can in there. The mixture is benign mixture of antifreeze and lube under minimal pressure (it's designed to clean out Pressure Washer pumps to prevent seal wear/freeze). Not enough pressure in can to harm heater core. You can buy it at Home Depot or Lowes, and flex line on can almost seals tight to metal heater core inlet.

Knocked the crud right out, then I did a antifreeze change to be sure, and all works well now.

 

I stand corrected.. Somewhere in my past research for this issue I understood there to be a heater core on either side of the vehicle.. In looking at JEPC I see there is only one..

Regardless I would still try flushing it.

 

How do we ensure that the control valves are open when we do this back flow wash out?

 

Hey Anxious Jim, having same problem as you did you ever solve it? Flushed the heater core no restriction at all no debris on flush either so plugged core isn't the issue. Thinking blend door as well but no idea which one could be suspect can't find a good exploded view of the heating unit anywhere! The one on alldata sucks!

 

Hi a biigdog, yes, mine was resolved by a new core. However, 3-4 weeks later I'm noticing that the drivers side is slightly cooler than right after the repair, but only slightly.
FYI, my mechanic also flushed it first & found nothing. I pretty much insisted that he change it & that fixed it.

 

I have not had a problem with my heater but from reading many posts on this subject this is the situation as I see it:

There are no valves involved when you do the flush.

The hoses go straight onto the core.

There is only one core which can be partially blocked.

The blockage is composed of a brown gelatinous material with some solid particles in it.

When the core is flushed, since the bockage is partial, the outlet flow can appear to be full bore but may not be successful.

Depending on how sticky the deposit is some flushes work, some do not.

 

Hi,

I am new to this forum site and have an issue with my XJ6 X350 blowing warm air out of the drivers side and hot air out the passenger side, I am aware this is a common problem with the X350.

I have been looking into running a sharp shoot of compressed air through the matrix then flushing it with water.

Has anyone tried this method and had any positive or negative results from this because the last thing I want to have to do is replace the complete matrix due to a blockage or a leak in the core.

All your advice will be helpful.

Cheers.

 

Well all I can say is it might help and should not damage the core if the outlet is open.

We have seen the picture of a deposit on this forum when a member cut open his blocked core.

The thing to do would be to find something that would shift the deposit eg
a solution of dishwasher detergent in warm or hot water. Ideally this should be done on the bench with a sample of the deposit.

 

My problem was a burnt out heater auxiliary pump. It's not hard to get out at least for the 2004. If facing the front of the car it's on the left side of the radiator towards the bottom. Had to disconnect some hoses and loosen the radiator fill box if anyone wanted the gory details =)

Just hook it up to a power supply and see if it spins up if not then needs replacement. Was 222.00 and change from the dealer which, surprisingly, was cheaper then online prices once shipping was factored in.

Hope this helps anyone else looking for diagnosis, this certainly should be checked before you pull the dash apart to go after blend doors /shudder.

 

Great info!! Mine was cold on the driver side, and hot on the passenger. Several coolant exchanges later it hasn't given me any more issue. Not to say it won't malfunction again...

 

I'm having the same problem with my '04 XJ8. I will give this a try and see If that solves the issue.

 

I did my coolant exchanges myself. I had to do it 3 times before the issue went away. I didn't flush it, and my coolant looked new. The key to mine was bleeding ALL the air. I know they should self bleed, but mine was very picky.. USE THE BLEEDER SCREW on top of the coolant expansion tank, it is your friend.