[RS61]

Hey guys. I have a 2021 M5 Comp. It gets used on track a lot so I use Castrol SRF. Today it went in to get the brake fluid replaced and the garage said they got most of it out but the two front calipers both had seized inside nipples so they couldn't drain those.

How dangerous do we think it is to not go and get this sorted and finish the bleed of the inside of those calipers? I dont know the physics of the fluid, and whether the old fluid will end up mixing with the new one, or just sit there at the bottom of those calipers potentially boiling. The garage seems to think it's fine and they got most of it out.

Also is there any best practice here for tracked cars eg replacing the bleed nipples with every fluid change?

[Maverik259]

i'd be more concerned about air bubbles than old fluid. What did they do to try and get it off? Simply brute strength? I mean if its truly seized thats not how you get a bolt off.

[pbonsalb]

If the car gets tracked a lot, I would try to free up the inner nipples even if that means removing the calipers so they are easier to work on. Use a good penetrant and after some time, try to crack them free. If one breaks, take the caliper to a machine shop to remove the broken part unless you are really good at fixing this sort of thing.

[RS61]

Ok thanks guys. Update, have decided to fix this issue now as if I leave it those nipples in place now, they definitely aren't coming out next time, and I do want to be able to fully drain the fluid. Getting the calipers off and sending them to Pro Calipers to get the nipples extracted, and to replace all 6 with stainless steel ones. Will hopefully prevent them from seizing up in future.

[AHall]

Originally Posted by RS61

Ok thanks guys. Update, have decided to fix this issue now as if I leave it those nipples in place now, they definitely aren't coming out next time, and I do want to be able to fully drain the fluid. Getting the calipers off and sending them to Pro Calipers to get the nipples extracted, and to replace all 6 with stainless steel ones. Will hopefully prevent them from seizing up in future.

Pictures would be nice for others that may encounter this.

[RS61]

Final update on this.

I don't have pictures of the seized nipples because they look just like the normal nipple (the black screw thing at the top of the calliper) and the only difference is they don't turn and won't come out, so the only way you find out is when the garage tells you they can't do the bleed.

In the end I got the garage to take off both front callipers, took them to Pro Callipers (found their details on a forum), and Thomas there took out the nipples and replaced them. He also noticed that the seals had cracked from the track heat (see photo), so did a full calliper refurb to get them back to original condition.

The callipers are now back on the car, all six bleed nipples have now been replaced with stainless steel aftermarket ones, and the brake fluid has been drained and replaced, so we're back in the game.

Main takeaways - if you're tracking or driving hard, then after 3 years or so it's likely that the calipers will have issues and it's worth getting them serviced by a specialist, as well as swapping out the nipples for stainless steel ones before they end up seizing.

[RS61]

Quick question for you guys. I did a six hour drive just now after all the work was done. The brake pedal doesn't feel right. It has about an inch of travel before it bites. After that the brakes are strong and totally normal. So now I'm trying to remember if that's how it was before, or if the bite was immediately. My muscle memory is telling me that something is off (air etc). In your M5s, is the bite absolutely immediate, or is there a tiny bit of travel before the car starts to slow?

[FC]

Originally Posted by RS61

Quick question for you guys. I did a six hour drive just now after all the work was done. The brake pedal doesn't feel right. It has about an inch of travel before it bites. After that the brakes are strong and totally normal. So now I'm trying to remember if that's how it was before, or if the bite was immediately. My muscle memory is telling me that something is off (air etc). In your M5s, is the bite absolutely immediate, or is there a tiny bit of travel before the car starts to slow?

An inch of dead travel is definitely wrong and screams of there being air in the system. I would bleed the brakes again.

[Maverik259]

Originally Posted by RS61

Quick question for you guys. I did a six hour drive just now after all the work was done. The brake pedal doesn't feel right. It has about an inch of travel before it bites. After that the brakes are strong and totally normal. So now I'm trying to remember if that's how it was before, or if the bite was immediately. My muscle memory is telling me that something is off (air etc). In your M5s, is the bite absolutely immediate, or is there a tiny bit of travel before the car starts to slow?

Definitely immediate. Did you bed the new pads? Assume you’re not running ceramic pads (not ccb obviously).

[RS61]

Damn, ok that's what my muscle memory was telling me too. Didn't feel right at all. Ok going back for a third bleed..

[JamieCali]

Thanks for helping me out. You made my day.