03-31-2024, 07:31 AM | #1 |
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OG F87 Rear Brake Caliper Bleeder Screw Causing Fluid Leak?
Moved car to make space for a garage door repair job, found liquid on floor, felt something bad happened, checked, it was brake fluid, found rear left caliper leaking into inside of wheel and ground.
History - Did a brake fluid change on 20 Jan, didn't notice any leak when taking it out for a drive on weekends - Installed M Performance style brake pad cover, used some force to push the rubber into place, car was not started so the pedal barely went down Would this damage the brake system? - some research indicated may be use to some extend, but wouldn't cause any immediate damage. Question: would this increase the pressure (like pumping)? - a friend came over, helped to take the wheel off using professional tools (my impact wrench didn't work, no breaker bar) used brake cleaner to clean up things, removed the dust cap to observe and diagnose easier, applied brake multiple times to see if it leaks from the bleeder screw, no leaks found... - 99% sure bleeder screw was the only point of leak, no other point of leak (part #10 in the diagram) - opened reservoir cap to check fluid level, still in between min and max (did this release some pressure? - took it out for 15 mins drive and check again, no obvious leak, weird My friend recommended keep watching / observing for a few days. After some research, the bleeder screw can be stripped or damaged. I reckon the simplest potential one-shot solution is to replace the bleeder valve (may be stripped or damaged somehow - based on the paint chip-offs on the caliper - some rude brake fluid job done by some before...) with a genuine BMW one? https://www.fcpeuro.com/products/bmw...ew-34116780509 Is it a DIY job or better to get it done at a workshop? TIA, any advice is appreciated.
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Last edited by terrywang; 03-31-2024 at 07:37 AM.. |
03-31-2024, 07:34 AM | #2 |
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Initial discovery, even some sign of leak on the top of the caliper, once cleaned up with wheel off using break cleaner, haven't seen this again.
So far bleeder screw is the single source of leak identified...
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04-01-2024, 08:07 PM | #3 |
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I strongly suspect that you didn't quite tighten the bleeder enough when you did the fluid flush. Then, pressing hard on the brake pedal while installing the covers was likely enough to push fluid past the not-tight-enough bleeder screw.
If it doesn't leak anymore after re-tightening the bleeder, you should be fine. By 'tight', I don't mean crank down as hard as you can. I typically tighten to just snug, then give it maybe a 1/16 turn of an additional tightening. Would be nice if there was a torque setting for those screws, but I've never seen one. If anyone has one, please enlighten me. If you torque it down too much you risk deforming the seat in the caliper, or stripping the caliper screw threads. At that point you are looking at replacing the caliper. |
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04-01-2024, 10:48 PM | #4 |
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@ggggbmw you may well be right!
After tightening it a little bit with the wheel off, it seems to have stopped leaking... I found the torque spec for the ventilation valve (bleeder screw), it should be 10Nm. The guy who did the brake fluid replacement job for me said he had never torqued BMW bleeder screws using torque wrench (hardly ever saw any leaks, now he has...). 34 00 Brake test and brake bleeding Tightening Torques Type Thread Tightening specifications Torque 1AZ Vent valve F80 / F82 / F83 / F87 WAF 11 10 Nm And more specific ones (for Brembo made ones - I believe OG F87 fixed caliper + front 4 pistons / rear 2 pistons M Performance brake was made by Brembo) there is even more specific ones: front 18Nm rear 10Nm
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04-02-2024, 07:27 PM | #5 |
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terrywang Thanks for posting that TIS torque info. I'll have to try it the next time I bleed brakes. (Soon. It's almost track season and time to put the SRF in.)
I'm curious where you got the link and info. newtis.info has been shut down for a couple years now. |
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04-03-2024, 05:37 AM | #6 |
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UPDATE: I have bought a 5-25Nm 1/4" drive torque wrench and re-torqued the bleeder screw, took it out for a spin (15mins), checked, clean no leak but I'll keep an eye on it in the next 48 hours to see.
If it continues to leak, I'll replace the bleeder screw. Hopefully, the caliper thread is not damaged (screw is aluminium? I reckon the caliper is steel harder, screw will be the first to strip?). I used a crawler to keep an offline version of the newTIS for OG F87 (my build only unfortunately) before it was shutdown. I thought I was accessing the online version...
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04-13-2024, 05:24 AM | #7 |
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Purchased bleeder screws (a pair), replace the existing one with a new one, it performs even worse than the original one(thought to be stripped).
I inspected the original one, it definitely has had better days (I can see marks of abuse by mechanics worked on it) but the treads are good. I used brake cleaner to give it a good clean and wipe, put it back in and hand tight, then torqued it to 10Nm, stepped on brake pedal immediately after several times, no sign of leak around the screw neck. One thing I noticed: there was blue threadlocker like stuff at that the original bleeder valve screw's neck (right below the hex that goes into the caliper threads). Does anyone know if blue threadlocker is used on bleeder valve screws? cc F87source Thanks in advance.
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04-13-2024, 05:38 AM | #8 | |
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I suspect the threads are likely damaged. My advice is try to tighten the valve by hand a bit more and see if the leak stops. If it doesn't then it's likely the caliper threads are unfortunately damaged. This means you'll need to either rethread it with a larger thread or helicoil or timesert it. The blue color you're seeing could be paint from the caliper body.
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05-21-2024, 07:11 AM | #9 |
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Update: May 2024
The car was left in the garage when I was travelling, for about 17 days. Upon my return, when checking the container around the inner wheel (as a bowl container), nothing, good sigh. Not even a drip, just a little bit of seepage around the screw neck, which wasn’t too bad at all. I was able to use kitchen paper to absorb it. Took it out for a couple of drives, check the screw neck every, it consistently seep that much (not up to a drip) around the neck and caliper screw hole, now using kitchen paper to wipe it off every time after a drive (thanks to the ramps) as temporary workaround. While in search for a permanent solution, I found some interesting screw designed for Brembo caliper ventilation valve leak issue (owner stated it is already the 3rd gen product). I'll order some (if they have the size (M10x1 30mm) anyway and ship it over to try(will be carefully check the threads before using it to avoid further damage to threads). Has anyone seen such design? Does it actually work? NOTE: pressing the brake pedal should be able to push the copper head / washer and o-ring out, right?
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05-21-2024, 07:12 AM | #10 | |
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Since it is not really leaking (rather, it is seeping slowly), I'll see alternative way (e.g. the new design screw) before taking it to professional brake / caliper workshop.
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06-14-2024, 11:08 PM | #11 |
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After researching and testing, I realised that 10Nm was for a different type of screw.
The bleeder valve used by OG M2 is made of steel, so 17Nm is closer to the range that Brembo recommends for M10x1 17-20Nm for car (12-16Nm for motorbike). I'll try 15Nm and observe. Reference: https://www.bremboparts.com/europe/e...caliper-280503
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06-26-2024, 11:56 AM | #12 |
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terrywang how's this working out for you? I have an M340i and was always torquing all to 10 Nm. Always got some dribbles that eventually stopped. Now I see in ISTA that front Brembos are 18 Nm and rear painted calipers (single pistons) are 17 Nm. I'm going to try this out, even though it's nearly double what I previously torqued at.
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06-29-2024, 05:53 AM | #13 | |
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Today I took the wheel off and torqued it to 17Nm, I'll continue monitoring it and see if the seep/weep goes away completely. NOTE: I've consulted many who work on cars / motorbikes, especially with Brembo brake systems, they all agree that 17Nm sounds about right for this type of steel bleed plug (M10x1), therefore the action today.
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08-10-2024, 06:34 AM | #14 |
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After several months of adjustments, trial and error, tightening the bleed plug (screw) to 17Nm seem to have been the solution - today I checked again after a spirited drive, no leak at all around the bleed plug neck finally.
This torque setting aligns with both the official technical manual and Brembo's specified range for M10x1 30mm bleed plugs, which is 17-20Nm. This suggests that 17Nm is the proper tightening torque, at least for me. Thanks F87source for echoing on this.
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08-13-2024, 07:52 PM | #15 |
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Thanks for the ongoing feedback on this topic. Never really thought about torque for the bleed screws before this. (Not sure why, I torque wrench nearly everything else.)
I have been using 10Nm since the early part of this thread, and that was about as tight as my typical hand tight. No leaks, even with multiple track days. But with the later info, I'll probably bump that up a bit the next time I bleed fluids. |
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08-14-2024, 12:39 AM | #16 | |
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Yes Brembo says you can torque up to 20 something NM and it'll be safe, but my personal opinion is to use the lowest amount of torque possible, and BMW has spec'ed anything from 10 NM up to 18 NM. So only increase torque if you find it is leaking and it needs more torque, otherwise stick to 10NM and increase only if necessary.
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