Leaking joint on Aluminium radiators

SMB · Jan 22, 2019

Hi,

Where the valves screw into the aluminium rads has started to leak (all be it not that much). The system is a ordinary pressurised sealed system. The leak is hardly enough to drop the pressure. The system has been fine for 4yr+, I guess that the rubber gasket has started to fail. I have tightened the joint a bit, seemed to work for 6 months.

Obviously (rad) the system needs to drained down and the joint sealed. What is the best sealer to use on the treads?

steadyon · Jan 22, 2019

1. Be careful, many aluminium radiators have left hand threads on one end, usually the right hand side. It's to make sure tightening up the tail nuts doesn't unscrew the connectors between sections.
2. The best seal would be cleaning the mating surfaces and replacing the rubber rings (normally "O" rings) with new ones.
3. If new seals aren't practical, I'd use Loctite 55. You'd need to rough up the male threads gently with a file.
4. If you can find the make / model of the radiator you can probably find the installation instructions on-line.

Stigster · Jan 22, 2019

SMB said:
Where the valves screw into the aluminium rads has started to leak (all be it not that much).

Do you mean the leak is at the threaded chrome "tail" that joins the valve to the radiator end caps or are the end caps themselves leaking where the caps screw in to the rad?

SMB · Jan 22, 2019

Thanks for your reply.

The leak is between the end cap and the radiator, not the chrome tails.

If I replace the o ring, what type of rubber should it be made of.

Stigster · Jan 23, 2019

To be honest I don't know what type of rubber they are made from (also some brands of rad use a flat fibre washer instead). If you go to a plumbers merchant and ask about aluminium radiator bushings and seals they may be able to supply them.

I'll admit that when I don't have any to hand I build up a washer/gasket with PTFE tape, not on the threads themselves but build up a seal by putting a load of wraps of tape at the flange and I've never had a problem with them leaking.