Bleed Nipple Leaking - but through thread?!

[TonyHetherington]

Hi all,

We're building a kit car, and on the rear caliper we have a fluid leak. It's coming from the bleed nipple, but not out through the centre hole - instead, up through the thread. We've purchased new nipples - still the same problem. We can't now work out where to go with it, short of a new caliper (which will be a big problem as they're a few years old).

Any thoughts? It's not a huge leak, but it's enough to collect in a drop or two on the wheel after a few weeks - so more than we want!

So, really I'm asking are there any nifty suggestions or thoughts on how to go about solving?!

Thanks !

[Mr2Mike]

Sound more likely there is a fault with the calliper, perhaps a hairline crack in the body?

[Nick3point2]

yep will either be the sealing seat in the calliper or a fracture allowing fluid to wick up the thread.

[Nick3point2]

try using some PTFE tape to see if it stops, AFAIK PTFE is chemically inert so won't react with brake fluid.

Not a permanent solution of course!

[TonyHetherington]

Thanks guys - it does seem like we're fighting a lost cause against either a crack or a manufacturing fault.

As you say, PTFE Tape won't be the final solution, but it may solve it briefly. Are there any other tests / possible fixes or are we destined for a new caliper? (You can tell we really don't want to do this!)

Thanks

[freecar]

You could try using a countersink bit on the hole in the caliper, if there is a burr there it'll prevent an oil tight seal.

[MikeyT]

My Wilwoods came with PTFE tape on them when new (on the threads) ... well, that's what the stuff looks like anyway

[phumy]

The bleed nipple does not seal on the threads, it seals on the caliper sealing face contacting with the nipple end face, if you have already tried new nipples and the result is the same (still leaking), then its either the caliper sealing face damaged or there is a crack (as mentioned before) in the threads. Mabye you can shine a torch down the threaded hole to see if there is any damage on the caliper face, not sure it you can re-surface a seal face but worth a try at a small engineering compnay perhaps. Otherwise, if it was me i would probably go for a new/reconditioned caliper.

Good luck.

[TonyHetherington]

Thanks both - yes that's what we had, unfortunately, concluded, too. With the system bled and raring to go we are just so very loathed to empty the caliper

Indeed - another one, I think it is.