Before I go digging, I would like to get a few opinions...

2005 XJR, quad zone climate control. I just did the valley hose replacement (had to disassemble and reassemble twice, don't ask but it sucked...) The car was apart for a few weeks as I can only work on it at night.

It is now running fine without leaks, but the front driver side vents and one of the rear vents are blowing cold and the other 2 are fine. i have read many threads that point to either a gunked-up heater core, bad auxiliary pump, or the dual climate control valve. I don't think it is the pump because 2 of the vents work fine, but I could use a few more professional opinions before I start ripping stuff up again.

 

The easiest way to test the pump is to feel it. You can feel it running. Second step, and also easy is to put an infrared thermometer on the intake side and the output side. Temp should be the same when running.


You can do this with the heater core as well but it's a bit trickier because coolant will still flow through a partially blocked core.

Are you sure you bled all of the air out? Easiest step here is to drive it up on ramps and bleed the air out by opening the SC cooling fill. I think that's the highest point in the car when up on ramps. Other should confirm my assumption.

These are simple tests you can do that don't require you disassemble anything.

Air in the system would be my first suspect since you had the cooling system open.

BTW, you can point the infrared thermometer into each vent during operation to get a good sense of the difference in temperature on each side.
There is a DTC for the RH or LH air mix servo. Code B2834. Is that what you mean by dual climate control valve? Are you referring to the servo?

 

"or the dual climate control valve"

Sounds like the valve in the S type.

It's not used in the XJ

 

Thanks Meirion. I thought I was having a senior moment.

 

Yeah you're right, I'm confusing this car with my old STR. I did a lot of that while changing out the valley hose which I did on the STR years ago... Same engine? Sort of, but that would be too easy.

 

At what point should I open the SC fill? Before the car is started or somewhere during the warmup process?

 

Sorry if I misled you. Don't have anything open during the warm up process. The proper bleed procedure is as follows:

6. Remove the coolant expansion tank bleed screw.
7. Fill the cooling system up to the MAX mark on the coolant expansion tank using a fifty percent mixture of Jaguar Premium Cooling System Fluid or equivalent, meeting Jaguar specification WSS M97B44-D and fifty percent water.
8.CAUTION: Do not over tighten the coolant expansion tank bleed screw. Failure to follow this instruction may cause damage to the vehicle.
Install the coolant expansion tank bleed screw. • Tighten to 3 Nm.
9. Install the coolant expansion tank pressure cap.
10.CAUTION: Do not RUN the engine with the coolant expansion tank pressure cap removed. Failure to follow this instruction may cause damage to the vehicle.
START and RUN the engine.
11. SET the heating system to MAX heat, the blower motor to MAX speed and the air distribution to instrument panel registers.
12.CAUTION: Observe the engine temperature gauge. If the engine starts to over- heat switch off immediately and allow to cool. Failure to follow this instruction may cause damage to the vehicle.
Allow the engine to RUN until hot air is emitted from the instrument panel registers, while observing the engine temperature gauge.

13. Switch off the engine.
14. Allow the engine to cool.

15. Release the cooling system pressure.
• Remove the coolant expansion tank pressure cap.
16. Fill the cooling system up to the MAX mark on the coolant expansion tank using a fifty percent mixture of Jaguar Premium Cooling System Fluid or equivalent, meeting Jaguar specification WSS M97B44-D and fifty percent water.
17. Install the coolant expansion tank pressure cap.

As you can see in step 14, allow the system to cool!!! Again others should chime in but I think the SC fill is the highest point (I no longer have my SV8), but once on the ramps, you can squat down eye level with the top of the engine and spot the highest point in the cooling system, so in theory you can top it off there but there's no reason the recommended procedure above wouldn't work. Please just don't open the SC fill until the engine is cooled down.
Having the car on ramps will allow the air to the top of the system more readily.

 

So I did the purge and now the back seats are blowing hot and the front is blowing cold. Any other ideas?

 

Forgive the obvious questions but you never know:
Front and rear controllers both in Auto?
What happens if you change the temp from max cold to max hot manually, any change in air temps?

It took mine ages for the coolant reservoir to settle after a thermostat change so I wouldn't discount air in the system yet. Have you taken it for a decent drive with all the seats set to full hot?

 

Well I've been driving it for a few days now, and I've tried a few different ways... First I drove around with full heat on all four seats set to panel and floor. Then I put the whole car on auto but it dropped it to 89 degrees instead of HI heat of course, but I drove it for a while like that anyway. Now since it is actually cold out I have the back seats on 89 at full fan panel and floor and the front on 89 panel and floor at the lowest fan setting so it isn't blowing cold air everywhere.

So this morning it changed, since it was 35 degrees outside I am now able to tell that what I thought was hot air is actually lukewarm air and it is once again doing the crisscross thing, cold on driver front and passenger back, and lukewarm on the passenger front and driver back. Judging by the seemingly changing patterns I am not ruling out air bubbles, but I hope it isn't a clogged heater core or something. Do you think maybe I should get a full chemical flush? I just flushed with water when I reassembled everything.

 

Have had a look in the workshop manual but it doesn't give any fault diagnosis for air temps, just codes. Getting the codes read might be your next step but given that the faults are transferring I still think it may be air. Have you tried manually selecting a gear to keep the engine RPM @ 3000 for a mile or two - the increased water pump pressure and flow may be enough to help any bubbles out. Do this with the heat on hi all around.

 

I will try that, but from everything that I am reading on other threads I am beginning to suspect the auxiliary water pump. Do you know if there is any way to test it without removing the coolant reservoir?

 

Second that aux pump. The exact same thing was happening to my SV8 last year. I changed the heater core, that helped, but still cool rear lower vent and front side one. One sure way to tell if the pump is bad is to put you hand next to that floor vent and rev up the car to about 3000 rpm or so. Hold it there and see if it gets warm again. Without that pump working, the water pump can't push enough coolant through the system at idle. Actually, I just noticed my car doing it again today! I usually don't drive in stop-and-go traffic so my car is rarely idling and I was always nice and toasty! But today, I was on my way to the university and I got stopped and had to wait for a few minutes to get in (Profs are on strike and picketing, but that's another story). I noticed I wasn't as toasty warm after a few min and checked the rear floor vent (since I recognized the symptoms). Guess what, cold/cool air. So I revved it up and it got warm again. Looks like the pump I put in is shot again (I did install a used one). Unless there is a fuse for the pump, which I can't seem to find) to check, I would say replace the pump! I'm going to have to do it again, but it's an easy job (done it a total of 4 times between our STR and SV8). I'm just SO glad they didn't use that stupid DCCV in our XJ's. Now those are a pain to change out!

Just noticed the Auxillary coolant pump is fuse 8 in the trunk. I'm going to check mine today.

 

Thanks, I am going to try that when I get out of work. By the way, rockauto has the aux pump for like $100 new, which is not too much more than I've seen the OEM used for... and you can look up the the 5% rockauto coupon online for a little extra savings. It is an aftermarket brand, but maybe it's worth a try?

 

Ok, so i first discovered that the aux pump fuse was blown, but replacing it did not correct the issue. So I replaced the aux pump and now the car gets toasty with the heat on. However, the driver seat is still blowing cool. Everything else works, so I think I can live with it, but it is still annoying. I am suspecting a clogged heater core, which I really don't want to do.