stevieweavie Posted October 29, 2012 Report Share Posted October 29, 2012 Been having trouble with my brake bleeding nipples. They first started playing up when I tried bleeding the brakes, once cranked open they started letting fluid out past the thread, so I replaced them with some new ones. These though started to weep a tiny bit out past the threads even when done up tight (the brakes were given a bit of abuse as i was blasting round cadwell). Any ideas how to stop this, or does it mean the thread on the calllipers are knackered Link to comment Share on other sites More sharing options...
blow_away Posted October 29, 2012 Report Share Posted October 29, 2012 Sounds like the thread in the caliper is worn out. You can try putting some PTFE tape around the bleed nipple as a temporary repair. EDIT - DO NOT DO THIS, read the thread below. Link to comment Share on other sites More sharing options...
Superdunc Posted October 29, 2012 Report Share Posted October 29, 2012 The thread on the calipers does not seal the bleed nipple. If brake fluid is weeping past the threads, it's because the seat at the bottom of the nipple is worn, damaged , or has dirt in it. Check there is not dirt in the caliper on the seat, and that there is no scoring on the nipple seat or the caliper seat. PTFE tape is not a repair. Sorry Al. Link to comment Share on other sites More sharing options...
theo Posted October 29, 2012 Report Share Posted October 29, 2012 Weld the fucker together. If you think that aluminium wont weld to a steel bleed nipple, you arent using enough heat. Link to comment Share on other sites More sharing options...
Cibbersicks Posted October 29, 2012 Report Share Posted October 29, 2012 The thread on the calipers does not seal the bleed nipple. If brake fluid is weeping past the threads, it's because the seat at the bottom of the nipple is worn, damaged , or has dirt in it. Check there is not dirt in the caliper on the seat, and that there is no scoring on the nipple seat or the caliper seat. PTFE tape is not a repair. Sorry Al. Yep, the conical seat is either damaged or got dirt in it. To be fair Al did say temporary, and it would stop it leaking to be fair, but wouldn't actually solve the proper problem. Link to comment Share on other sites More sharing options...
Superdunc Posted October 29, 2012 Report Share Posted October 29, 2012 Yep, the conical seat is either damaged or got dirt in it. To be fair Al did say temporary, and it would stop it leaking to be fair, but wouldn't actually solve the proper problem. Sorry wasn't meaning to be rude to Al or anyone else. Not keen on temporary repairs to brakes though. Link to comment Share on other sites More sharing options...
kanerdog1x1 Posted October 29, 2012 Report Share Posted October 29, 2012 could it be that you have bought new nipples and that they are stainless? i have found that stainless ones are hard and dont always give enough to seal nicely. i have mostly gone back to zinc plated steel ones, oe are best, after flirting with the trick ones...... Link to comment Share on other sites More sharing options...
Bernster Posted October 29, 2012 Report Share Posted October 29, 2012 Well mine's as clean as a surgeons finger nails but the rear on the race bike still weeps. The constant bleeding appears to have bored - out the thread so PTFE tape is the only way to go unless you tap the thread out to the next nipple size and fit a larger one, which will be my next move should the PTFE tape need too many layers. Link to comment Share on other sites More sharing options...
Superdunc Posted October 29, 2012 Report Share Posted October 29, 2012 Well mine's as clean as a surgeons finger nails but the rear on the race bike still weeps. The constant bleeding appears to have bored - out the thread so PTFE tape is the only way to go unless you tap the thread out to the next nipple size and fit a larger one, which will be my next move should the PTFE tape need too many layers. The seat is damaged, the threads do not seal anything. PTFE tape is not a suitable repair for brake systems. Sorry to sound like a broken record, but I find brakes to be fairly critical to peoples well being. Link to comment Share on other sites More sharing options...
BudgetBoy Posted October 29, 2012 Report Share Posted October 29, 2012 Have to agree with Dunc on this.The seat its the bit that is damaged NOT the threads.By putting PTFE tape around it may stop the leak but the overall problem will still be there.. One day when you need the brakes your TEMP repair will (possibly) give way to a shower of brake fluid and no brakes. I have found on various calipers i have done for people that the bleed nipple can vary on the seating bit profile.Easybleeds are different to the bog standard ones.If the angle is different on the seat is damaged it will leak and the only repair is a new caliper or machine it again/fit bigger bleed nipple. Heres some pics.if you look closely you can see there is a slight difference in angle on the nipple seat.If you new nipple is identical to your old one then the seat is ruined. Link to comment Share on other sites More sharing options...
blow_away Posted October 30, 2012 Report Share Posted October 30, 2012 The thread on the calipers does not seal the bleed nipple. If brake fluid is weeping past the threads, it's because the seat at the bottom of the nipple is worn, damaged , or has dirt in it. Check there is not dirt in the caliper on the seat, and that there is no scoring on the nipple seat or the caliper seat. PTFE tape is not a repair. Sorry Al. Every day's a school day! Thanks SD. So, what to do next? I've got the same problem on the steelie calipers using stainless steel nipples from HEL. I've not been riding the bike, but I was thinking about sticking it back on the road. I can't see that tapping out to the next size nipple is going to solve the seating problem, and I guess that buying some second hand calipers is going to be a lottery, chances are they are going to be in the same state as mine? I'm minded to try some brand new OEM nipples first as the easiest potential solution. If that fails what should I try next, given that new calipers will blow the budget completely? I guess what I am asking is if anyone knows what method is used to machine the seat into the caliper, and if it is possible to machine the seat slightly deeper to achieve a good seal? Link to comment Share on other sites More sharing options...
stevieweavie Posted October 30, 2012 Author Report Share Posted October 30, 2012 Thanks for all the replies. The new nipples are, as kanerdog suggested, stainless, so i'll get some steel ones, plus I'll check for dirt or damage on the seating face. I'll check the angle of the face compared to the old ones too, since i kept them somewhere. Link to comment Share on other sites More sharing options...
Superdunc Posted October 30, 2012 Report Share Posted October 30, 2012 Al, get an old bleed nipple in a lathe and drill ot the centre to 5mm, you can then use this as a drilling jig. care fully grind a 5mm drill to the same angle as the bleed nipple seat. Srew your modified belled nipple into the caliper then with the reground drill bit at a very slow speed you can recut the seat in the caliper. Link to comment Share on other sites More sharing options...
Pat Posted October 30, 2012 Report Share Posted October 30, 2012 Going back to wrapping PTFE tape around the thread dodge, I don't see how this would make any difference anyway. Surely for the fluid to get to the threads it has to first get past the seat & if it can do that then it would just flow out through the bleed hole of the nipple as normal as this is located in the unthreaded portion of the nipple. As this is open to the atmosphere (OK, with the exception hopefully of a dust cover) it's the path of least resistance & wouldn't allow any build up of pressure required to force fluid through the threads? Link to comment Share on other sites More sharing options...
RonniB Posted October 30, 2012 Report Share Posted October 30, 2012 The tape only really keeps air from entering the caliper during bleeding, not keeping fluid in.. Link to comment Share on other sites More sharing options...
lorenzo Posted October 30, 2012 Report Share Posted October 30, 2012 As has been said PTFE tape is a nice way of making the bleeding process easier, preventing air being sucked back in past the threads and/or, fluid leaking out instead of into the tube or whatever's on the end of the nipple. It's the seat that does the sealing, not the thread. Brake cleaner and an old cable tie to try and shift any lodged in grot from the bottom of the nipple hole. I just said nipple hole, something I never thought I'd say. Hmm. Link to comment Share on other sites More sharing options...
Bernster Posted October 30, 2012 Report Share Posted October 30, 2012 F***k me! PTFE tape is stopping my fluid coming out and any air going in as my rear works and bleeds air when undone, well it did at Darley, Donington and Mallory. Having said that, to keep the peace I'll go get a new nipple and fit it, if it's still leaking, I'll .... put PTFE tape around the new nipple too. *Edit: PTFE & not PETF. Link to comment Share on other sites More sharing options...
blow_away Posted October 31, 2012 Report Share Posted October 31, 2012 Cheers Dunc I was thinking about this, I suppose my mind had tricked me into thinking that my bodge became a permanent fix. Fortunately a long dig into my big pile of crap masquerading as a valuable spares resource turned up a pair of calipers, so I now have three ways of fixing the problem. Link to comment Share on other sites More sharing options...
Bernster Posted November 1, 2012 Report Share Posted November 1, 2012 New one arrived, see photo below. Fitted it, even though it's new the tip of the taper is considerably less pronounced on the new one, either way no weeping tits as of yet. Link to comment Share on other sites More sharing options...
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