Hi everyone,
The heater in my 98 xjr s/c v8 has gone, before I get a new valve or pump, I was thinking of flushing the system and matrix to be sure of no blockages! Any does or don't s or a thead to bleed system correctly?
Thanks Geoff

 

When was the last time you used your heater, and more to the point did it blow hot?

I'd guess the last time it was cold enough, i.e. months ago....9/10 it's the pump, if you remove it and strip it, regrease spareingly the nose of the spindle and button it back up, you can then rig it with a couple of lengths of hose to test it with a bucket of water.

If not then it'll be the valve, again these can be sticky if sat so a mild tap will energized can bring it back also.

Why look for more issues and potential airlocks with a system bleed? Check the parts and fix it before doing things like that and life is simpler

 

Thanks for the replying, I've only had the car for just over a year and it's the first winter with it. Was sort of warmish over this summer and into winter then a really cold morning here ( I work nights ) after work (6am) it was -2 on dash and no heating in car.
The advice your giving sounds great as I'll give it a go but I'm no expert, but I'm wondering if you need to bleed the coolant and the best way to do that ?
Thanks again Geoff

 

You will find instructions on bleeding the cooling system in the DIY Sticky.

 

Where would the valve be? My heater blew cold this morning and was working fine last year.

 

The pic shows the water flow through into the matrix. You'll need the special pliers to release the clips and backflush through the R/H pipe (backflow).

The valve is the black topped pot to the left. The heater pump is almost immediately below it on the chassis rail.

 

A yearly routine on my '01 : flush / backflush the heater core. Get heat back each time. I thought it was pump and/or valve at first. 4th winter in a row now where the flush does the job.

 

Just to clarify, and sorry if this is a stupid question, but when you say, "The heater pump is almost immediately below it on the chassis rail," you mean a separate, motorized pump that pushes hot water thru the heater coil box when the heater is on? Does this pump work only when car is on (or off)? I know some German car have an electric heater coil pump so that the heater will continue to work when the engine is warm, turned off, and only the ignition is turned to the on position.

I have has a low heat producing heater since I bought this car 3 years ago. I can get it "hot-ish" by turning temp all the way to high and then adjusting fan, but otherwise it/I never warm up.

 

The pump does allow water to pass through in "off" mode, if memory serves. However, when it's actually working, it pushes it a lot more effectively (just youtube the people testing them, you can see the giant jump in flow once power is applied). I had this same issue, and the pump was an instant fix once I replaced it. I believe the pump runs with power regardless of the car actually running, but obviously the temp will depend on the temperature of the coolant running through it, since it's only a pump, not a second heater. But if I turn my car off, but leave the heat on, I still get the heat so I'm pretty sure it's still pumping full without the car running.

 

Just a suggestion here... Unless the car isn't being driven, why not several times throughout the year turn the heater on full blast for about 5 minutes? Going on a long road trip over the spring/summer and you're by yourself? Open all the windows if it's hot outside and turn it on. It'll save a lot of aggravation when you really need it in the winter time and you won't have to flush it out.

 

+1 on this one!
That's what I do to maintain heat since I reverse-cleaned my heater core.
Kind of silly to drive in tropical temperatures with the heater full on, but I hope it will prevent the core from clogging again, and have heat for those few days it is required.

 

I agree, it is stupid to drive around in 90+F temp with heat on. It's because all other 'normal' vehicles already have hot coolant flowing thru the heater core year round and with just the engines water pump circulating it. I guess Jaguar didn't feel like adding in a blend door into the climate control box behind the dash board to seal off the heater core from the evaporator.