Heater mystery - Solved

Thermostat perhaps, that could cause the flow to stop to the heater matrix, Could somebody confirm

Hi David,
What does the temp gauge do if you hold the revs up at 3,500 for about 20-30 seconds?

The temp gauges rises slightly and the radiator fan comes on.

Blockage in the radiator or a rad pipe?

Pipework seems all free flowing and the rad too.

The rad fan seems to be coming on quite a bit more than I'd have expected, considering we're into Winter.:shrug:

No ideas?

Today I was trying to track it down, and had the car ticking over for quite a while. The rad fan came on, but when I felt the radiator feed pipe it was cold.

No ideas, yet?

An AA man told me the head gasket's probably gone.

David Aiketgate wrote: No ideas, yet?

An AA man told me the head gasket's probably gone.

The AA man could be right!!! I had a similar problem on a 2.3 litre Ford Granada that I had some years ago, was loosing coolant in small amounts but no external leaks, fluctuating heater temperatures (it also had Air Con) hissing from expansion/header tank cap sometimes spraying out coolant. Local Ford dealership could not find anything wrong, uprated the values of the pressure caps on the radiator and header tank, replaced hoses and clips and changed coolant. The following day I did a journey to Bristol, M3, A303 & A36. Very very hot when I got there, hissing from header tank fluid spray around top and coolant level down. Topped up coolant before I left about six hours later. Was about a mile before the start of the M3, on the A303 doing 70mph and there was an almighty “Bang” with steam coming from under the bonnet and the temperature gauge dropped to zero!! Stopped as soon as I could and discovered that the rear core plug had blown out and had lost all of the coolant. Drove a short way to a filling station and called the RAC for recovery home. The engine would not restart to drive onto the trailer. The problem was quickly found when the head came off ~ the aluminium head had cracked on the centre two combustion chambers, between exhaust valves and a waterway. The exhaust gasses were pressurising the cooling system to the extent that the expansion cap was giving relief, and as the engine cooled down the coolant was being sucked into the cylinders and blown out the exhaust on restarting. The final straw must have been the uprated pressure caps so something had to give!!!! The engine was repaired by the leasing company (Ford Dealership) and sold at auction!!!
You may be faced with a head off job. :rant:

Simon had the answer. :yesnod:

David Aiketgate wrote: Simon had the answer. :yesnod:

Yes, yes..... so thermostat? Come on David a little more detail, photo's and a new how to surely If it is just the thermostat why where you losing coolant?

:yesnod: Anyway glad to see it's sorted. Fingers crossed.

The thermostat is stuck closed. :yesnod:

I thought the clue about the fan running even when the radiator feed pipe was cold would have given you it.:shrug:

Once I changed the cap the coolant loss stopped. May be the stuck thermostat had put too much pressure on the old cap.:shrug:



I have the PRT system fitted, and it seems that the bypass circuit is sufficient to allow enough coolant to circulate to prevent the engine overheating even with the thermostat stuck closed. With the normal thermostat setup the engine will tend to overheat more readily.

PRT replacement How to on its way!