Leaking Rad Tail

14 Jan 2005
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United Kingdom
Hi Guys,

I have replaced an old 960mm radiator with a new Type 11 600mm x 900mm rad, using 2 x 30mm tail extensions to fill the gap.

My problem is on one side where the rad tail screws into the extension piece. I am using both PTFE and jointing compound and just can't stop the joint weeping when I pressurise the system. I have no leaks at the extension/rad joint or at the valve. Its just the extension/rad tail joint.

I have wrapped 15 turns of PTFE (clockwise) and smeared it all with thread with jointing compound (White Boss). Should the rad tail/extension piece be screwed up to max effort? It is reasonably tight and didn't want to swing off it any more in case I damaged anything.

I'm just getting fed up with draining the rad each time to redo it. Would more PTFE turns fix it?

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I wouldn't use Boss White with PTFE - it may degrade the tape. Normally 15 wraps should do it, provided you've wound it on in the direction that screwing the extension in doesn't "unscrew" the PTFE. You could try:

a. Do it again with more PTFE.
b. Do it again with Loctite 55. Follow the instructions for use, and wind it across the threads in a form of random pattern, don't wind it purely with the threads. Better still if you rough up the threads on the extension with a file before applying, but don't overdo it. Rough a bit, try in rad with no Loctite, and stop roughing before it wont screw in with a bit of resistance.

In either case it needs to be tight. Use a 10" or 12" wrench and do it up until it takes a fair bit of effort to move it any more.

The threads on the extension should be tapered, those in the radiator will be parallel. The seal is formed by the wedging action of forcing the taper into the parallel.

Good luck
Thanks oldbuffer, I'll give the Loctite 55 a go first as a 'search' of the stuff seems to suggest its far superior to PTFE.
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