Zero Brake Switch Leaking!

[Guest Dickie]

I thought I'd have a go at the brake pipes this afternoon, all was fine until I filled the system & found the brake light switch leaking at the four way union. I have removed, refitted & tightened as much as I can, but it still seeps out.

Does it need a washer? ptfe? or putting in the vice to tighten?

[Shaft]

You will probably find you have a 3/8 unf brake light switch and a

M10 x 1.0 union. It's a common oversight as they do appear to fit, but

won't seal correctly.

HTH,

Nick.

[Guest mcramsay]

the brake light switch is a tapered thread, so technically a washer shoud not be used. on tapered threads the sealing is done by the clearance between the threads, obviously the more you tighten the tapered thread into the union, the clearance becomes less until oil cannot pass. if you have a mismatch of threads then no matter how much you force it in there will always be a leak path as the thread pitch might be the same but angle of the threads different. normally you would apply PTFE tape on tapered threads. washers/dowty seals are normally for parallel threads. if you have leakage and its tight, then as stated above, you prob have a mis match of threads. if you remove the sender you will prob see the threads on the brass union have distorted a touch. you can either, bang some PTFE tape on, and you will prob find it will seal, but its a bodge, you can get some loctite hydraulic seal which is great stuff. last thing is to get the correect threaded sender for the union you are using.

 

 

not ranting atall ! i just spend days at work watching apprentices putting PTFE tape on parallel threads and then wondering why the pipwork drips like a f**ked fridge when it gets a bit of pressure in it!

[Guest Dickie]

Thanks, I'll have another look tomorrow, bought both parts from GBS three weeks ago, thought they would match?

[Guest mcramsay]

they might well do, i always use PTFE on tapered threads, as sometimes they will leak without, it depends on the quality of the parts. stick some PTFE or thread sealant on, that will most likey cure the problem. if you use thread sealant, then clean the union of brake fluid with some degreasant, and then put some thread sealant on the sender, wack it in tight, and then leave to cure for a few hours before putting pressure on it.

[fry61]

 

 

 

not ranting atall ! i just spend days at work watching apprentices putting PTFE tape on parallel threads and then wondering why the pipwork drips like a f**ked fridge when it gets a bit of pressure in it!

 

Steady grand-dad, you'll be telling us next how it was before television.

[sj-bradley]

What's television?

 

 

Simon.

[biksz]

its a thing with black and white pictures i think.but no sound lol