Seeping Nipples…

Hi all, I’m after a bit of advice. Have just replaced front right-to-left brake pipe on my 99 C4. Have done a fluid change / bleed. 24hrs later the bleed nipples are still seeping fluid. I did fully dry them off after bleeding in order to monitor. I did them up ‘wrench tight’ but is it likely I’ve just not tightened them enough? Should I remove them completely and check / clean the threads - if I do this; any top tips for avoiding losing loads of fluid? I’m hoping the calipers aren’t damaged - it didn’t take crazy force to undo them. The nipples were replaced relatively recently. I’m just paranoid about over-tightening and stripping the caliper. (I realise they don’t look pretty - that’s a job for later. I’m just trying to get it back on the road and driven for a bit before the salt arrives). Thanks in advance.

Not tight enough. Will only need the very slightest couple of degrees and it'll be fine. It's a case of clean it off, tighten a couple of degrees, press pedal HARD, check if it weeps, tighten a bit more if needed.

Clean the threads by all means but the seal is the taper that matches the caliper so make sure that's clean and not damaged.

I take it they didn't leak before so they should be correct taper for the Brembos. Strange that they are both leaking! They don't need much tightening at all in fact be very careful, you can easily strip the threads.

Thanks everyone. I’ll carefully tighten them a touch more and check. They didn’t leak before hand, and pretty much all are seeping. Odds are they can’t all be ruined, so likely me being too cautious. I’ll report back.

I'll be honest, my heart always misses a couple of beats when I do mine and I always have the same problem where they weep until I get it just right.

I've just changed the brake fluid on mine. I never do them that tight as over a couple of years they tend to get tighter by themselves due to corrosion building up in the threads. This time I had one that weeped and had to do it up tighter than I wanted to, still not that tight and far from snapping. It's impossible to know how tight you've done yours over the internet. There are a couple of possibilities, 1 you've done them no where near as tight as they should be and there's nothing wrong other than you need to tighten them a bit more. 2 you've done them to an appropriate tightness and there's dirt in there, or the pointy part of the nipple, or seat in the caliper is damaged. Tightening much further risks snapping them as they are not as strong as normal threads of that size due to being hollow in the middle. 3 your replacement nipples have the wrong taper angle meaning they need to be tighter than normal to seal. If you did want to take them out to inspect the nipples themselves and the threads in the caliper, put clingfilm under the reservoir cap. I bit of fluid will come out but not much and you won't get air in the caliper.

Good points from @Mac996t I will add: Sometimes they are tight enough but once they have a few heat cycles the residual fluid in the bleed nipple can creep and make it look like they are leaking. Clean down with brake fluid reduces the fluid creep mentioned above You can mark them before you crack them open so you know you are in the right ballpark. Always use a 6 sided socket to initially crack and to tighten them. Use a torque wrench to take the guesswork out of it, start not very tight and add a bit more until they stop leaking. If fluid IS getting out then air can get IN. Depress the brake pedal an inch or 2 to close off the feed from the reservoir to prevent much fluid leaking out if you inspect or slacken the bleed nipples (cling film only works if the cap is ventilated not the reservoir) With any of the above assume a bit of air has crept into the calipers so an extra bleed maybe necessary. Good luck.

Ok, update. Thanks all again for answering the call. Some really useful tips and there and information to weigh up the next steps. As they were all weeping, I decided they were mostly likely not sufficiently tight so I set up to re-bleed. Before starting, I put the torque wrench on the ones that were weeping to get an idea of where I had got them to. I worked up to 15nm and got no further movement on them (however, suspect trying to tighten an already tight-ish nut from standstill gives a different result from moving it up for a less tight position…?) So after bleeding again, went to 15nm with the torque wrench. There was still a little seepage on some so then went another couple of mm, heart in mouth. Cleaned and dried everything up, stood hard on the pedal and all is good. Time will tell if I’ve overdone it. The car is new to me and the calipers have lived a full life. Looks like they’ve had heat previously (maybe when corroded nipples were replaced) and at least one of the caliper to hub mounting bolts has been helicoiled. Once it’s back on the road and I’ve exhausted some other jobs I’ll probably take one of them out and inspect the shape of the end, as 15nm+ does seem quite high? For now I’m just pleased to be another step closer to getting back on the road before packing up for winter. Thanks again

as Mac996T says if they're replacement nipples, and they're tight, which they are, in fact too tight they supposed to only need 6nm, then I suspect you've need new/correct nipples as the angle is incorrect and isn't sealing on these nipples.

........or the 25 year old Aluminium mating face has some corrosion.

Like all trouble shooting its best to look what’s new or changed.

Quotes source post: 2830705

Or some gorilla has overtightened them in the past and "rearranged" the taper in the caliper. You then fit new bleed nipples and the new nipples don't match up with the "rearranged" tapers in the soft aluminium of the caliper. Solution, ? As others have said, keep gently tightening them until they don't leak. Stainless bleed nipples seem to be more problematic than the OE mild steel items.