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  #1  
Old 01-19-2012, 01:16 PM
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Default 98 XK8 Heater not working well

On my 98 XK8, the heat inside the cabin is less than luke warm, even after being run for awhile. I can regulate the temp from freezing (a/c) to a little less than what I consider warm with the A/C controls, fan speed works fine. This is the first time I have really driven car in the cold since my ownership of it. I have seen some posts for common heater pump or valve problems. I found the pump on the driver side firewall and when the car is running I can touch the pump but do not feel/hear any noise. Is there a certain time when the pump should run? I have tried having heat and fan at various settings.

Some questions:
Does it sound like a heater pump to you guys?
To check the obvious, which fuse controls the heater pump?
If the pump is bad, how in the world do I get to it? It is buried way in there... Anyone have a how to diagram or something?

Thanks in advance.
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Old 01-19-2012, 01:35 PM
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Hi does it get any warmer when the a/c is off? I run mine at 23c and it keeps the cabin snug without any condensation.

Good luck Al
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Old 01-19-2012, 03:14 PM
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Let the search button be your friend. Here is the same question posed within the last couple days with more replies:

Heater issue

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Old 01-19-2012, 03:23 PM
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I can regulate the temp from absolute freezing with a/c on to slightly less than warm with a/c off, temp on hi (one button press above 90F). I will have to check temps of the 4 houses on the heater valve and the two on the heater core with my new laser temp gun. The heat is almost warm at best. I would expect to be roasting with a heater set on hi. I have checked coolant, squeezed hoses, its full, and appears clean.
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Old 01-19-2012, 04:08 PM
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If you can get some heat at high engine rpm then it's probably the heater pump.
This from the uk jag forum....
Hot water for heating the cabin air is supplied from the engine coolant system via a solenoid operated control valve and circulated by an electric pump. The pump is energised in all running modes except low coolant temperature of in panel off mode. The pump is off with ignition on and engine not running. The water valve is used to regulate water flow to the heater matrix and so regulate outlet air temperature. so if you check the pump the car will need to be up to temperature At low engine speeds the water flow in the engine is lower than that produced by the electric water pump therefore the non return valve is positioned in the engine cooling system. This is to prevent the electric pump recirculating water to the inlet side of the heater, against normal engine coolant flow. A second non-return valve is positioned in the heater circuit to prevent hot coolant convection back into the heater after the engine has been switched off.
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Old 01-19-2012, 04:45 PM
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I've been experiencing the same thing this winter...thought it was my imagination. So, I should check out the little pump I guess.

CJ; I hardly drive mine so let us know what you find.
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Old 01-20-2012, 02:05 PM
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Have you recently, or since the last time you knew the heater worked right, had the coolant flushed and re-filled? If the heater is air locked from a coolant drain and refill you'll need to push the air out. Some of these cars never see the high side of 2500 rpm.

Note that you wont get any heater circulation until the engine coolant is above 120 or so. Easy way to know when the pump comes on is to put the HVAC control in AUTO and temperature to HI while the car warms up. Once it reaches temperature the fan will kick on and you can assume the heater pump is trying to run.

Assuming the pump and valve still work:
  1. When cold check your coolant level and make a note how full it is. Use your IR temperature gun to note the temperature.
  2. Set Heater controls to HI and AC off. Fan at some speed (NOT OFF).
  3. Warm the engine up then run engine at about 3000 rpm steady for a couple of minutes. (you might suddenly find you have heat).
  4. Let the car cool completely down and check your coolant level to see if it has dropped -- Do this at the same coolant temperature that you did in #1
  5. If the coolant level was reduced then you had an air locked heater core.

The easiest way to access the valve and pump is to remove the throttle body. Not as hard as it sounds. And, don't forget that fancy cable operated hose clamp tool. Well worth the $45 at sears.

My heater will burn my feet on a cold day with the top down.

Mike
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Last edited by OregonJag; 01-20-2012 at 02:15 PM. Reason: Added warm up note
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Old 01-20-2012, 03:18 PM
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I chased my tail for weeks trying to diagnose the problem with my heater, I could only get hot air at high rpm.
Was it an air lock, a stuck valve, a kinked hose, the wrong antifreeze (can turn the coolant to jelly apparently)?
It turned out to be the electric heater pump. The dealer said most likely the valve on an S-type and the pump on the XK.
You may have a different problem of course, this forum is mainly for folks to fix their own cars but it helped me to understand the set up when I finally gave up and got the dealer to fix it.
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Old 01-24-2012, 01:53 PM
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Ok, I did some investigating, and pardon my crude diagram. My heater valve pump does not appear to be running at any air conditioning or heat setting with engine on. I can put my hand on the little pump, and feel nothing at all. I hope that the culprit has been identified.
I also noticed that (when looking at the firewall from the front of the car), the top right hose (Valve "C") is not warm at all. This hose goes to the right most connection on the heater core and is not warm, and appears to have even collapsed somewhat. I assume this is the source of coolant flow from the valve to the heater core, and therefore interior cabin heat. Does anyone happen to know the flow of coolant through the valve so I can increase my understanding?
Heater Valve/Pump
PUMP
*******
___| |_____
A__ __---->C
| |
___| |_____
B__ _____D
| |

Heater Core Lines
Left Right (Hose "C" from valve)
O O

P.S. - Thanks for the tip on the cable hose clamp tool from Sears. My wife ordered it for me and it is on its way, it was even on sale! It looks like a handy tool for the man that has everything. I also managed to find the same heater valve/pump assembly from a breaker yard in the UK that had the same part # listed on ebay. It was about $45, shipped, can't beat that. I hope to receive the part soon, and install. I will post back when I fix it.
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Old 01-24-2012, 02:22 PM
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The valve and pump are two completely different units.
The valve is easy to see and reach, but not so the pump.
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Old 01-24-2012, 03:00 PM
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This is the picture of the part that I am referring to, I assumed the pump was attached to the valve assembly as a unit. Part # on mine is MNA6711AC.
Jaguar 97 XK8 Heat Heater Valve Control MNA6711AC The top right hose that feeds to the heater core from this valve is not warm.
If this is only the valve, where is the pump? so I can try check that too.
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Old 01-24-2012, 05:18 PM
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Yes that is only the valve, which is probably ok.
The pump is above the gearbox. The dealer charged me $800 to fix it, about 3hrs labour.
Look at FAQ part one XK parts PDF page 179 for a diagram of the system.
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Last edited by malbec; 01-24-2012 at 05:24 PM.
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Old 01-24-2012, 07:11 PM
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The pump sits above the tranny. I have pics where the tranny was out and the pump was replaced, but not removed from a top down position. But here's what it looks like from below. There is also a tutorial on how to repair/rebuild the pump if I can find it.


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Last edited by oldjaglover; 01-24-2012 at 07:21 PM.
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Old 01-24-2012, 07:50 PM
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Here: Jaguar XJ6 Aux heater pump
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Old 01-25-2012, 11:13 AM
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Thanks to everyone for all of their suggestions pics and diagram reference. This helped me understand more of what I was looking for. I jacked the car up, crawled under it and finally found the pump.
I turned the car on, let it run to operating temp and still did not hear any pump running. I tapped the pump with a long extension and hammer, no noise from the pump. Maybe I have finally found the cause.

Now, on to the fun part of removal. I can see the a few bolts that I should be able to get to from the underside of the car. In everyone's experience, is this the easiest way? I figure if you remove bolts from the underside, and possibly remove the throttle body, you may be able to wiggle your hand in there from the top of the engine bay enough to replace the pump and remove the two attached hoses. I bought one of those cable hose clamp tools, so when I get it, I can begin the process. It looks like the pumps run about $150+ used, but found a person on ebay selling rebuilt for $175, may be worth the extra.

I'll keep everyone posted, but it may be a few weeks until I find the part and get my tool and time to tear into it. By then, it might even be warm outside!
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Last edited by MR. CJ; 01-25-2012 at 11:15 AM.
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Old 01-25-2012, 12:10 PM
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Have you verified power all the way to the pump in both off and on? Sometimes the sensors and/or fuses/relays can be the problem.

Take a look at the repair link. It looks like an easy project once the pump is out. It is a two piece assembly with the motor pushing a magetically pulsed pump. If your current flow is good and your motor isn't turning you can replace the brushes very cheaply. The pump part can be cleaned and inspected.

Once again, Jaguar has taken a very simple principle and mechanism and turned it into a government-type experiment in unnecessary complexity. I'm sure it created a few more jobs, though.

Just a thought: What happens if you bypass the pump completely? Leave it out and join the hoses? Our systems have plenty of pressure to cycle water anywhere...unless the design of the heater core is so poor it takes a "boost".

Anyone?



Good luck.

Last edited by oldjaglover; 01-25-2012 at 03:33 PM.
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Old 01-25-2012, 02:07 PM
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I have thought about this too. Is it possible to bypass the pump altogether? Maybe to at least help me make it through the cold season. Would you just have to connect the two hoses feeding into the heater pump? I know the system may not be as "efficient" especially during the summertime, but it doesn't seem efficient to have frost inside the car with no heat working either.
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Old 01-25-2012, 03:32 PM
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Hmmmmm....

Ya know, it might just be worth a test if you have the motor/pump out, or if you can get a nipple to fit between the two hoses (or replace with one continuous hose). I seldom need mine, but the whole setup just seems unnecessary....especially with the amount of pressure our water pumps make.
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Old 01-25-2012, 04:38 PM
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The pump isn't a pulse pump but rather a centrifugal pump. The odd part is that the motor has no physical connection to the pump but relies upon magnetism to transfer motion from the motor to the pump. As such it will be very prone to clogging/sticking but the upside is there is no shaft seal to leak. One might try disconnecting the hoses leading to the pump and flushing forward and back through them with a garden hose to restore function.
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Old 08-08-2012, 01:56 PM
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Since I am waiting on some parts and tools to arrive for my chain tensioner project, I decided to go on a fishing expedition for the auxilary water pump that was the suspect part in my no heat issue. After about 2 hours of scraping my hand on every piece of metal in the firewall that I could find, using the wire clamp removal tool, some surgery with a knife, and some prying off of the hoses, I managed to remove the heater valve and heater pump assembly as a connected unit from the top of the engine bay. Removing the throttle body definitely made the job easier. I tested the valve and pump with 12V power and the valve opened and closed fine, the pump was dead and would not operate. The replacement pump that I bought was definitely whirring away when power was applied. I reinstalled everything carefully, connected all the hoses and everything looks good. I can't test the operation of everything until I get the tensioners done, but I am confident that the pump was the culprit. Total cost was $45 used pump from eBay, and about 2-2.5 hrs of my time, and of course the clamp removal tool that I already had, about $30. I don't want to think about heat just yet considering that its summertime, but it will be nice to know that I will have heat when it gets cold.

After completing this repair, I really wonder why the heating system had to be that complicated?
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Old 08-08-2012, 01:56 PM
 
 
 
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