Leak at Heater control Valve - Herald 13/60

[Antonnick]

After removing the whole heater unit to test the heat exchanger for water tightness, I am now sure that the very minor water loss is where the rubber sealing ring is fitted. 

Before I refit everything - should or rather can the Rubber O ring be smeared with something to help it seal. Grease, vaseline, ????

[glang]

Hi, obviously the sealing surfaces have to be clean and smooth but nothing more needed for sealing. You could put a dab of oil to stop it sticking next time you dismantle it. The replacement o rings are not the same as the original rubber seal but I found them perfectly ok.

The other place the valve can leak of course is from the operating spindle...

[Antonnick]

Ok, thankyou Glang. The leak is most defiantely coming from the O ring and perhaps if I had known this before, it would have saved me the trouble of dismantling the whole heater unit. But never mind, it meant I could clean it up a bit. 

The leak was very small but I found that after maybe two weeks there was a drop in the coolant level of the radiator and some wetness inside the car at the air distribution unit.

Perhaps the flange nuts were not tight enough - at least I know for certain the heat exchanger is not leaking

[RobPearce]

On my Spitfire I cleaned the surfaces up with a bit of wet-and-dry then fitted a slightly over-sized O-ring that I had in a box of assorted sizes. Seems to have done the trick.

[Antonnick]

A bit embarassing really - upon reconnecting everything it and after a short run to warm the engine up - one of the hose clips to the heater unit was faulty. It appeared to be very tight but in fact had an obstruction in the mechanism and did not adequately secure the heater hose - hence the leak.

Oh well, at least I was able to clean everything inside the heater unit 😑