Ok, new member here.. I just got this XJ8 a week or so ago. I've had this issue from day one. I purchased the car without testing the heater as it was a warm day. When I turned heat on, I realized at a stop there was zero heat, just cold air. As I get up to speed, the passenger side heat gets really warm, and the driver is luke-warm. I drove the car from Kansas City to Wichita this way, and had no other issues. It never overheated, but I could hear the cooling fans running at full speed when I came to a stop. (A/C NOT ON).

I have worked on cars all my life, and decided to poke around, as I suspected a cooling system problem, and IME most likely an air pocket. I read this forum and others, and attempted to bleed / burp the system. I drained the radiator, refilled with distilled watter 8 times (drive / drain cycles) = 8 gallons. Upon last drain I refilled with 2 gallons of DEX-COOL Prestone antifreeze (full stregnth). It took 2 gallons because I lost almost an entire gallon to bleeding. I filled the expansion tank to the full mark, ran the engine at 1500RPM (cap on, good pressure on hoses), turned on heat with same poor heat results. I let her cool, opened the tank, and it was full. I then found a "bleeded screw" on the expansion tank, and opted to remove it.. I started the car (heat & A/C off), cap off, bleed screw removed, and let it idle. Soon I had antifreeze and tons of bubbles, and volcanic eruptions of antifreeze from the bleed hole. This was a violent sight.. Steam was spewing, bubbles, antifreeze.. I thought she was overheating, but the temp guage was normal. Several times after this eruption the expansion tank would completely drain in to the engine to empty (cluster read "engine coolant low". I refilled with DEX-COOL. Then eventually the magic happened.. All this violence ended, and a steady stream of coolant was pouring from the bleed hole. The temp guage went from dead middle to approx one needle width below center, heat worked great from all vents. PROBLEM SOLVED!!! NOPE!!

After all this, I drive her 800 miles to Indiana.. No issues at all during this trip! Checked coolant level the day after I arrived home, cold, and it was full and orange. I decide to visit my dad (45 mile drive), and no issues until I put it in park. I notice driver side heat going cool, then passenger went cool. Temp guage is fluctuating between the middle mark, and the mark just below the middle. Little to no heat at all. I also hear the fant running on full speed again. I let it cool, check coolant, and it's still full. So I open the bleeder screw, and cap, let her idle, and we go through the mess of spitting bubbles and steam again. After 20 mins or so of this (ONLY OUT OF THE BLEEDER HOLE, HEAT / A/C OFF) and the routine of adding coolant as it sucks it down, and blows it out, she stabilizes. Heat now works great, temp guage back to just a hair under ceter..

My thoughts are possibly a head gasket leaking combustion gas in to the cooling system, but I'm praying this is not so. I can not afford such a procedure after dropping close to $10K cash on this car. I did the "balloon" test after it stopped acting out, and the balloon never inflated at all after 20 mins. So that almost rules out the head gasket.. I am now asking for your input. Water pump?? Thermostat? I'd greatly appreciate any help in this matter. If I can't get this issue resolved, she will be going back up for sale and I'll have to cut my losses. I, however won't hide her problem from any new prospective buyers.

I have to take her to the dealership at some point for free recall issues. One is break "pipes" and the other is a reflash for emissions.?.? I will be posting another thread for my only other issue: Harsh 2-1 downshift from long drives to a dead stop. Doesn't do it all the time, but it's annoying.

Thank you all for taking the time to read my novel!

 

New member here, 2nd post in the "help me" section lol. I have done hours of reading on this issue, and am here for advise. My 04 XJ8 has 101K miles, and after highway driving almost always surges from 2-1 downshifts. Normal city driving doesn't seem to affect it. However after highway driving it will continue to downshift harsh (2-1). I have an appointment at a local Goodyear Service Center (There are NO Jaguar dealers within over 100 miles of me) for a transmission flush. I have read forums for HOURS on this subject, fluid types, etc. This shop is doing a complete exchange (no filter / pan just the fluid). They will use Castrol Multi-Import Vehicle fluid. After researching, this seems to be 100% compatible, and no ill results from others that used it. I read on roadfly forums that if these ZF trannys get even slightly low they will act this way. I also read that this could be an adaptive driving issue witht the car, and it may need flashed as well. I will order the pan / filter online, and have it replaced as well shortly after the fluid exchange. Any idea on how much it will be to "flash" this system to the latest firmware? There is a recall sticker under the hood from 2004 for a TCM flash. I called Jaguar and there are two active recalls on my car. One is brake pipes, the other is a flash for the emissions. I asked about flashing the transmission, but the lady didn't seem to think they would do that. Any ideas, or advise is more than welcome. I love this forum, and thank you in advance!

 

Silting-up of the heater core in the climate control box is a known fault, and can produce the symptoms you describe of heat one side and none the other. If its not that, it is a fault with the air blending flaps. Each side is independent of the other.

 

A TCM reflash is fairly routine and costs little, mainly the time, about 30 minutes. The software is downloaded from the Jaguar JDS. Reflashes are needed as the box wears over time. If your car has never had one, then its overdue for that mileage.

However fluid change would be beneficial too.

 

Thank you, I appreciate your input. However, it heats absolutely even, and perfect so long as the guage reads a hair under middle. When the heat gets erratic, the cooling fans hit high speed, and it will spit antifreeze, air, and steam from the bleed screw when opened (after cool down, and at idle.) The 2 times I've had this issue bleeding the system has resolved the uneven heat. I believe this is something else, but thank you for taking time to submit your advise. I will make a video of exactly what happens IF this issue resurfaces.

 

Also as stated above, whenever the heat goes cold, the temp guage will always fluctuate between dead middle, and the line below dead center. The radiator fans always come on high. The guage never reads hot, and the info center never says engine temp high.

 

Thank you for that benificial information!

 

Another question just hit me. Would it be safe to remove a batterty cable and let it sit for a few hours? Maybe that would clear the "history" of the prior owners driving habits. IDK if this would work or not, but I am a new owner, with my own driving habits, so maybe it can relearn my driving style once reset. LMK what you think.

 

You have put a lot of effort into solving these problems and have made progress but you have had the car a very short time.

Can you not take it back to the dealer and ask for your money back?

 

I bought her private party and paid cash. I drove 400 miles to pick her up. Unfortunately the nearest dealer is over 100 miles away, and after dropping almost $10K cash (no financing) I'm in no position to pay dealer shop prices this soon after shelling out this kind of dough. On top of the purchase price I paid gas for 1 car there, and 2 back, almost $90 for a Mobile 1 oil change, approx $75 for coolant & distilled water, and a tire rotate & balance, new wiper blades. New SilverStar Ultra headlights were $54, and a few misc bulbs out around the car. Phew....

 

Pressure in the cooling jacket after the engine has cooled down does indicate HGF. However, have you thought about the thermostat failing, or starting to fail ? For HGF, most shops should have a tester that checks to see if there is any combustion products in the coolant.

 

I have yet to get it in to a shop. However, the cooling system loses pressure after a good 30 minutes or so after shutdown. Hoses become soft, yet still warm. The cap can be removed and no pressure at all is in the expansion tank after she cools down for a half hour or so.

 

So no HGF failure, or so it seems !! I would look at the thermostat. Others on here may have other things to check too, so wait to see if anybody else posts.

Water pumps on the early V8s were known to "lose" their vanes, but this was sorted before the X350 came out, or so I believe.

Other thing there is according to my Technical Notes of 2003, is the Auxiliary Coolant Pump which assists water circulation in the heater core. My V6 does without this.

 

Thank you for the additional info! Hopefully a few others will chime in and I'll get started ordering parts..

 

I'm just admiring the word 'Lurge' which is so nice it ought to be added to the dictionary to signify a lurking lunge/surge. 'The tiger lurged at me'.

Your transmission will learn your 'style' eventually but you can do a reset by removing battery earth and touching the earth lead to batt +ve for a few seconds.
Only do this if you have (or need) the radio codes.
If you look in the XK8 stickies there's a list of things to do after disconnecting your battery.
I'm not convinced your non-Jaguar dealer can reflash your TCM.
Changing the fluid will do nothing but good.
Keep us informed.

 

The ZF trouble shooting guide from Jaguar says:

"The transmission adaptations are NOT cleared by carrying out a hard reset. The transmission adaptations must be cleared manually using the dealer special tool."

 

Thank you, and I should have been more specific on the TCM flash. You are correct, the Goodyear Center can not do a flash, as far as I know only Jaguar can do this flash. Goodyear is doing the complete fluid exchange for $85USD using Castrol Multi Import.

 

That's interesting, I'm not at all convinced about that and it is not what JTIS leads one to believe.
As I understand things fully discharging the TCM capacitors will make it lose its 'adaptive' learning but not the programming.
Can you post or quote the document you got that from please?

 

Not sure if it is the same issue, but my thermostat was stuck open on my car and if stopped, the heat worked ok, but when on the highway at speed (with all the cold air through the radiator) no heat. It eventually set off a CEL. $20 part and should be an easy swap (mine still has warranty). Probably worth a shot.

I think you might have a different issue, namely, a coolant leak. I know you say the res is full, but the pressure loss so quickly after parking is suspect to me. I have been working on cars for eons, but new to jag so I am not sure what the most likely suspects are. If it were a land rover I would know where to look.

 

Yup, here you go.