My heater didn't work at any temperature setting, but I could not convince myself that it was the water control valve that was at fault.


I found one article that described the way this valve functions. It indicated that under normal operation the maximum voltage to the valve occurred at minimum temperature settings. This would stop all flow to the heater core. The minimum voltage to the valve occurred at maximum temperature settings. This allowed full flow to the heater core. If this is correct, a power failure to the water control valve would cause the heater to function at all settings. Mine did not function at all.


Also, the heat on each side of the vehicle is controlled by a separate valves. If one valve failed for mechanical reasons, the heat to its respective side of the vehicle would not function. Malfunction of the heat on both sides would indicate a mechanical malfunction of both valves. Since my water control valve appeared to be fairly new with no signs of corrosion, it is unlikely that there would be a mechanical malfunction in both valves.


This would imply that the most likely cause of the heating problem is an air lock in the heater core. This is a known problem in the S-type, and I have found several variations on procedures for bleeding the air out of the heater core. I have tried them all several times, but the heater still does not work. There must be a better way!


After scratching my head for a while, I came up with the following:


1. You will need the following materials (See the photo):


* one piece of 3/16 OD clear hose about 5 feet long
* one bottle (a 16 or 20 ounce soda bottle will do well)
* extra coolant
* some tape to wrap on the end of the tube to make it fit snuggly inside the bleeder valve
* a small bucket may also be useful





2. Begin with the engine cool enough to remove the filler cap from the coolant reservoir. Remove the cap so that all of the pressure in the coolant system is released. Find the heater bleeder valve located between the coolant reservoir and the break fluid reservoir. Remove the plug from the bleeder valve and insert one end of the hose. The end of the hose can be wrapped with tape to make it fit snuggly. This is not a high pressure system, so only a snug fit is necessary. (See the photo below.)





3. Let the other end of the hose fall over the fender, and place it in the soda container which is sitting on the ground. Poor a inch or so of coolant into the soda container so that the end of the tube is submerged. This will prevent air from being drawn back into the system - much like bleeding brakes. I often place this container in a small bucket to help keep it upright and to catch any overflow.








4. Make sure that the coolant reservoir is full and replace the cap so that coolant is not forced out the top of the reservoir. Start the engine and allow it to come to operating temperature. Set the temperature control to HI, turn off the A/C, and direct the air output through the upper vents so that it is easy to feel when the temperature changes.


5. Bring the engine up to about 2500 rpm and hold that speed for a minute or so. You may or may not see any coolant moving through the clear tube. Drop the engine back to about 1500 rpm and hold that speed for a minute or so. Repeat this process until fluid begins to flow through the tube. This will usually first happen when the engine speed is reduced. Once the coolant begins to flow, increase the engine speed back up to about 2500 rpm and hold that speed and then drop it back again. Experiment with variations on this pattern.


There will probably be gaps in the flow of the fluid where air is being forced from the system. If this should stop the flow of fluid completely, increase the engine speed for a moment and then drop it again. Keep repeating this process until there is a continuous flow of fluid. This can take a surprisingly long time. It took me almost 15 minutes to purge all of the air from the system.


DON'T FORGET TO REFILL THE RESERVIOR FREQUENTLY. Since the system is open, there isn't any pressure in the system, so the reservoir cap can be removed without worries. Don't forget to replace the cap. This will prevent fluid from being forced out the top of the reservoir. Also, the engine can be allowed to idle at any time. The fluid in the receiving soda bottle will prevent air from being drawn back into the system.


As air is removed from the system, water will begin to circulate through the heater core, and the heater should begin to work normally.


I hope this works for you as well as it did for me.

 

Bugga, now I gotta go out in the heat again and see if we have a heater bleed valve.

I dont recall seeing one on either car.

Both cars have no/little heat, and also the taps look newish to me.

Glad the beers COLD.

 

Mmmmmm, we dont have that either.

Different header tank, and hose set up totally.

Our tank has 1 hose for filling the system, and 1 smaller hose at the top for the single bleed hose.

My parts book shows the LHD set up, that is complicated in my opinion.

Anyway, thanks for the write up, but it looks like it is LHD specific.

 

The early cars are a bit different.

Can't a similar thing to a brake bleeding kit be done such that it fixes in place of the expansion tank cap? That would work with all the cars.

 

JagV8,


I suppose that such a setup is possible. I don't see any reason why it would not work.


Jim

 

JagV8,


I posted another thread about modifying the radiator bleeding system.
https://www.jaguarforums.com/forum/s...solved-108429/
That adapter could be modified by temporarily replacing the brass plug with another barb fitting. This would allow the attachment of a bleeder hose without modifying the coolant reservoir. However, I am not sure that this would help resolve an air lock in the heater core.


The bleeder valve for the heater core is attached to a pipe that comes from the return side of the heater core. This allows a more direct connection to the heater core and may be more efficient than bleeding the primary system.


It is possible that using the modification of the radiator bleeding system would help bleed the heater core as well, but I think the only way to know is to try it and see. Maybe someone with an older vehicle will try it and let us know.


Jim

 

OK, thanks. The reason I asked was that if a modified cap would do then it's much simpler. (It won't be suitable for the early cars as they have an extra bleed line that's not needed - or at least not present! - on the 2002.5MY-on.)

I've bled mine OK just by leaving the cap off. May have been lucky, though.

 

Several people have mentioned that their vehicle does not have a heater bleeding valve and have asked for a simple way to bleed the system without using the heater bleeding valve. I have used the following modification, and it appears to work. It is based on a modification of the main coolant system bleeding valve, which I posted here:


https://www.jaguarforums.com/forum/s...solved-108429/


This change requires two additional parts which should be available at any decent hardware store.


1 ea. Brass barb fitting 1/4 inch ID x 1/4 inch MIP
1 ea. fuel valve for a lawnmower


Install the modification as shown in the following photo.







After installing the modification, you should close the red fuel valve. Fill the reservoir with coolant and replace the cap. Start the engine and allow it to reach operating temperature. Open the fuel valve, and coolant and trapped air should flow out of the tube. When the catch bottle is almost full, close the red fuel valve and pour the coolant back into the reservoir. Add additional coolant as necessary. Repeat this process until air no longer flows from the system. Close the red fuel valve again. Bring the engine up to about 2000 - 2500 rpm and hold it there for a couple of minutes. Let the engine drop back to idle and open the red fuel valve again. Repeat this process until all of the air is removed from the system. Once the air is out of the system, turn the engine off. Open the reservoir cap to release any pressure in the system. Replace this modification with the original brass plug. Fill the reservoir with coolant and replace the cap.