My heat works well on the passanger side but not on the driver side, the dealer said it must have a blockage in the heater core and wnats to put in a new core for $1000. Only 35K miles just out of warranty!!! I can't believe its the heater core blockage because I get heat on the passenger side.

 

I don't know the details of the climate control system on your model, so to me that explanation seems impossible.

 

I don't want to undermine your mechanic's diagnosis but with heat coming out that is a pretty darn good indication that the heater core is working to some capacity. As with all cars, you can check the two heater hoses that go into the fire wall in the engine compartment. After the motor warms up feel the hoses, if both are cold, heater core is probably dead, if one is warm and the other isn't then it's probably a circulation issue. If it was me, I would try to pull the heater hose and flush the core and then top off the coolant to see if that helps any.

 

It would have to have two separate heater cores, in my mind, and I doubt it. More likely they just split the upper and lower heater/ cooler rotary flapsand servo control them independantly. One side has a control or feedback pot problem, so it's not positioning correctly. But I don't know the hardware on this model, so all of this is just hot air.

 

usually is a problem with heater cores.. only on the R's not so much on xj8.. ive replaced maybe 6-7 already.. also had doors or the casing warped..

 

_genius, thanks for jumping in. It's one heater core that doesn't provide even heat? That sounds surprising.

 

our engineer told us the casting or mold for the heater core when its made.. gets stuck in the core.. and over time blocks it one half .. on this car there is no dual coolant control valve.. the core has 3 connections.. so top half and lower half.. and flaps adjust the ouput temp with a feedback temp sensor

 

_genius, thanks for that. bniland, looks like it's going to take more than my hot air to keep your feet warm.

 

jag_genious i have the same problem is exspensive to fix the problem?

 

couple hours.. to re-re dash.. i cant remember how much the part is..

 

I believe it is the heater core as previously diagnosed. The core is long and the drivers side is at the far end and is the first part to plug. If you actually measure outlet temp at each dash vent you will find the farthest left(LHD) the coolest with the temp going up as you move to the farthest right vent. You can back flush the core easily as the hoses are easy to access. At the same time you can reverse the hose connections at the core to continue the flush as you drive. Cheap fix for out of warranty cars. You may also want to examine the debris that comes out of the core. I've seen several plugged with casting sand and if that's the case all the flushing in the world wont stop the problem from recurring. I've replaced engines for this problem.

 

Thank you all for the advice Real-Tech I imagine from your response the best thing to do would be to replace the heater core? is the core itself very accessable? I found the core on line new for $135 how long should it take to replace it?

 

If you're an experienced technician the jobs not that bad. I think another tech said 2 hours but I feel that number is optimistic unless you've done 10 or so. The dash does have to come out or at least mostly removed to get the heater box out far enough to access the core. You could lay the dash on your lap and work over the top of it but any way you slice it a/c has to be discharged/recharged coolant drained, filled and bled and you don't want any mess in the car. I would do the back flush first and see what comes out of the core. If it's mostly black pieces that look like paint chips I wouldn't worry about it too much. If it is a white or coolant dyed white crusty crap I would pull every core plug out of the engine block and flush and scrub that sucker for days and after that is done replace the core and hope for the best.

 

Real_Tech,

What model Jaguars have you replaced engines in because of core sand in the cooling system? I presume this would only be necessary on a vehicle with a severe or recurring overheating problem, and I have not seen or read of this problem before on later Jaguar engines.

For a fact, this was true on early V12 as I have had to dig out chunks at the base of cylinder liners. What later engines have you seen that are similarly affected? Thanks in advance.

 

I've only seen it on '04 and newer XJ models and only a couple that required engine replacement. I swear I flushed these things with all core plugs removed except the one behind the starter for days, used chemical flushes and manually scraped any areas I could reach and replaced the heater cores. 6 months later the cores were plugged with sand again. I haven't seen one in a while like this and I assume specific VIN range is involved But I couldn't tell you the range as there is no bulletin or SSM for this. All were done under warranty with prior Jaguar approval. The most common blockage is a black plastic looking substance. I think it may be casting flash from the radiator tanks but it may be some sort of leftover from production. If you get the black stuff during the back flush it's usually fixed though a repeat may be necessary.

 

Thanks R_T,

I couldn't have gotten a better answer, and the same could be said by bniland.

 

I think I might have the same problem on my XJ8 2005. I have no heat on the left side and the right side is not very hot. At which connection are you guys flushing. I see a connection from the hoses to alum lines right near the ABS unit. Are you using tha connection and how does it come undone it looks like it does not use a hose clamp but a weird clip of some sort. Do I need a special tool?

 

I just bought an 05 XJR with same problem. Did you ever get a reply on where to disconnect hoses to flush the heater core? Thanks.

 

Very interesting thread. I've been very frustrated over the past month by a heating problem in my 04 xj8. Plenty of heat out the floor level vents but tepid to cool air out of the face level and defroster vents. Shop replaced the thermostat and housing but no improvement. Auto or manual control makes no difference. Would you think your heater core comments apply in this situation?

 

Follow-up. Took the car back to the shop and they tried to back flush the heater core. Weren't successful. Flow definitely restricted in one direction. New core being installed, thankfully under extended warranty. Not happy about taking the top of the dash apart but don't see a viable alternative. Will update as to whether or not this cures the problem and whether or not I have rattles or fit issues that weren't there before.