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I own a 2001 S type which I love but is proving problematic in the heating department.
I had a new heater valve fitted 3500 miles ago and from memory everything seemed ok, I do 3000 miles per year, this winter I seem to have a problem as follows.
The heater starts to work after 5 to 6 miles' a long time after the temp. gauge is at normal, I recall before the new heater valve it started working as soon as the car came up to temp. Instead it now blows ambient air as if the sensor is telling it to blow hot to get the cabin up to temp, then at about 5 miles the blower switches off and hot air comes out without the blower on and the cabin soon gets up to temp.
After about 30 minutes the warmth stops and I am back to ambient air again even when I push the temp. up to high, it seems to do this for a few miles and then warm comes back.
I have seen the tip about blowing the sensor out just above the dash dimmer wheel, I will try that, in case it doesn't work has anyone got any other ideas.
I am not a mechanic by any stretch of the imagination so it will be a garage job but just want a few pointers if needed.

Robert

Hi Robert and welcome.

Have you checked that the the external temperature sensor is giving the car a realistic reading. If a high reading the system thinks no heat is required. When they fail they usually give a high temp reading.

Doug.

Thanks Doug, a good suggestion but I had a new one of those fitted about 2 years ago and it seems to be pretty accurate but I will double check.

Regards

Robert

There is also a cabin air temperature hot wire sensor behind a small grill to the left of the steering column.

Pull the grill off with a finger nail and look inside the aperture. The hot wire is to the right and is very delicate. This aperture can get blocked with dust, fluff and muck. Blow out with a piece of pipe or a kiddies straw or gently clean with a small paint brush. That might help.

Also check for a coolant system air lock. I`ve sucked and blown mouth to header tank before now to clear a stubborn lock. Please don`t swallow the antifreeze!

Mike

Hi Mike,

I am sorry to ask such a dumb question but where exactly do I put my mouth to suck and blow, I presume the header tank, but where is it and what does it look like.

Robert

The header tank on an early S-type is mounted to the rear of the off side top suspension mount, below and in front of the black windscreen scuttle panel. You will see the black plastic screw on cap on top of the clear plastic header tank itself. It is very close to the off side bonnet hinge. Do not confuse with the brake master cylinder cap which is mounted on the big short black cylindrical brake servo, lower down and more towards the centre line of the car.

Unscrew the cap when the car is cold and ensure the coolant level is up to the appropriate mark. With the cap off, warm up the car to full operating temperature and watch for any air bubbles appearing. With the cap off, it makes it easier for any trapped air within the system to be expelled. Watch also for a good coolant flow via the small pipe at the top of the tank. Investigate if flow is slow or non existent. Squeeze accessible coolant hoses as an additional air expulsion method. Refit the pressure cap ensuring it is fully tight and that coolant level is then on the hot mark. Only top up to the indicated mark as an air gap above the top surface of the coolant level is needed for coolant expansion. Now retry the heating in the car.

My suggestion of giving mouth to mouth suction to the tank to help evacuate air should not really be necessary if you carry out the above. Certainly to be avoided if at all possible. The slight possibility of mouth full of antifreeze is not really recommended as it is poisonous. A good garage should have a suction tool which is a much better method of getting airlocks removed.

See how you get on now.

Mike

Thanks Mike,

I think even I can follow those precise instructions, I will let you know how I get on.

Cheers

Robert

Hi Ken,
I am pleased that you mentioned that ethylene glycol is a toxic poison. There are cases of domestic animals being killed by walking through puddles and then licking their paws. As little as 30ml can be fatal to human beings. Now theres a thought!

As Robert was enquiring where the header tank/ stroke filler cap is, is it possible that the cooling system is simply low on content?

Doug mentioned that the outside air temperature senser (the one under the front bumper I presume) could be defective. Is this the same sender that gives the outside air temperature reading on the air con panel? If so, would you get a hint from that reading as to the serviceability
state?
Regards
Oldtimer

Hi Mike, done what you said, coolant level looked a fraction low, so topped up, heated to normal op. temp. then put the heating on, no difference I am afraid, the 2 pipes that come into the top of the tank were nice and warm so presume warm liquid going through them but no warm air in the cabin. I also blew the sensor out in the cabin as well. Outside temp sensor showing 5, which is about right today.

Any other ideas Mike or anyone

Regards

Robert

Following my problems with the heater I followed the advice and whilst I didn't think it had worked, it actually had. The upshot of it was I needed a new header tank, I hadn't seen any fluid on the garage floor so it was a very small leak, but a leak nonetheless. The new header tank is now fitted and everything is fine and working as it should be.

So thanks Mike for your advice.

Hi ritakins
I think you must have had an airlock from ths previous valve job. When the new header tank was fitted the right procedure was carried out to bleed the system.

Jeff.