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Discussion Starter · #1 ·
I had a very weird event about a week ago and google wanted me to stop searching about it so much that chrome decided to crap out on me.
After some spirited driving, I usually let the car cool down by driving at lower speeds with low revs (shift at 2K).
It was all fine and I parked it around 1PM at my place. Until around 7~8PM, when I was about to have my first meal of the day.

I start the car, let the SA pump do its thing and I set off. The car slows down quickly as soon as I let the foot off the throttle. Maybe the engine brake is stronger than usual :unsure:

I get out on the road and immediately, I almost stall the M5 at the light. And at this point I'm like WTH!

I made a three point turn and parked the car again. The front right brake is blazing hot and I almost burnt my finger. (Never touch a hot brake rotor with bare hands. Actually don't ever)

Anyways, I assumed it was a sticky caliper where the pistone couldn't retract and am looking for front calipers. And since we don't have a lot of E39 M5s here, I was wondering if I could steal 540i/530i brake parts and fit them to the M5 such as caliper pistons and guide pins (bushings). Is this a possibility?


The only weird thing is that after that incident the car acts fine now. Brakes feel okay and no torque steer or whatsoever.
 

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Discussion Starter · #3 ·

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I had a very weird event about a week ago and google wanted me to stop searching about it so much that chrome decided to crap out on me.
After some spirited driving, I usually let the car cool down by driving at lower speeds with low revs (shift at 2K).
It was all fine and I parked it around 1PM at my place. Until around 7~8PM, when I was about to have my first meal of the day.

I start the car, let the SA pump do its thing and I set off. The car slows down quickly as soon as I let the foot off the throttle. Maybe the engine brake is stronger than usual :unsure:

I get out on the road and immediately, I almost stall the M5 at the light. And at this point I'm like WTH!

I made a three point turn and parked the car again. The front right brake is blazing hot and I almost burnt my finger. (Never touch a hot brake rotor with bare hands. Actually don't ever)

Anyways, I assumed it was a sticky caliper where the pistone couldn't retract and am looking for front calipers. And since we don't have a lot of E39 M5s here, I was wondering if I could steal 540i/530i brake parts and fit them to the M5 such as caliper pistons and guide pins (bushings). Is this a possibility?


The only weird thing is that after that incident the car acts fine now. Brakes feel okay and no torque steer or whatsoever.
Just a side note- You don’t want to start it and “let the SA pump do its thing”.
950506
 

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Discussion Starter · #5 ·
No worries 🤣
My SA pump is pretty loud and I don't want people to think I have a old diesel car. Unless they do already 🤔
I usually start the car, buckle up, play a music through BlueBus, and then I set off. Which takes about ~40 seconds. Unless the manual wants us to drive immediately, immediately.
 

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Sorry I wasn't clear. I was wondering if parts of the calipers such as pistons or guide pins would be interchangeable from 540/530 variants and the M5 ones so I could use it to rebuild it.
530/540 parts are relatively easy to acquire whereas on the M5 side, there is no possible way to get a brand new pistons.
Pistons and guide pins are the same size in 540 and M5. Calipers itself are different, imo.
Just rebuilt my front calipers with packet what was mentioned to be 540.
 

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You might want to diag that properly before you jump down the rabbit hole. A stuck caliper is a good idea but it can also be the ABS hydraulics. Take the offending wheel off then try and pry the caliper open, next break the bleed screw while prying, close the screw while still prying. Then start the car press the brake and repeat with the car running. If the caliper releases easily when you open the bleed screw then it is likely not the caliper.
Note the details in the different tests and report and I can likely give you more insight.
 

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Discussion Starter · #8 ·
You might want to diag that properly before you jump down the rabbit hole. A stuck caliper is a good idea but it can also be the ABS hydraulics. Take the offending wheel off then try and pry the caliper open, next break the bleed screw while prying, close the screw while still prying. Then start the car press the brake and repeat with the car running. If the caliper releases easily when you open the bleed screw then it is likely not the caliper.
Note the details in the different tests and report and I can likely give you more insight.
Hey Sailor,

Interesting. I will be fitting akebono pads while taking a look at the calipers. I didn't order any parts except for the boot which seems to be something that can be done preventatively.
I will report back with the results on the test.

The weird thing is that I'm pretty sure all four brakes locked up.
Thinking back, I didn't get any sort of torque steer at the incident. I only touched the front right brake as that was the one that was squealing and originally assumed that was the culprit.
So it would be either all four, or at least one from each side.

ABS hydraulics eh? Finicky electronics? What's a good search keyword for that issue? I thought most ABS problem was abs electronic problem, not the hydraulic section.

Cheers,
Gabe
 

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Discussion Starter · #9 ·
Pistons and guide pins are the same size in 540 and M5. Calipers itself are different, imo.
Just rebuilt my front calipers with packet what was mentioned to be 540.
Thanks for sharing your experience.
I'm also pretty low on budget, but I can take free parts out of the for parts e39 which my mechanic owns :).
The parts e39 is usually a 530i or 540i, so I might be able to score a good OEM piston at no cost!
 

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Discussion Starter · #10 ·
@Sailor24
I'm at the shop right now. Every other thing works and the front left caliper isnt getting any fluid. I pulled the DSC pipes and V is getting oil from the cylineer. VL isnt getting any fluid from dsc.
vr seems to be getting fluid.
 

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Thought that might be what you found,not specifically, but... Brake calipers don't seize in the conditions you reported and they usually make the car shake like crazy and un seize when given a small break once they are hot, at least the first time the symptom appears.
There was a recent thread where someone tried to fix the hydraulic unit. Not sure if it will help or not as I have never tried it, I have only done there first step and bought a complete unit and switched out the module to reuse the one that was in the car after testing it to make sure it is not a fault.


[SOLVED] Stuck ABS module valve - can it be rebuilt at home?
 

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Discussion Starter · #12 ·
Thought that might be what you found,not specifically, but... Brake calipers don't seize in the conditions you reported and they usually make the car shake like crazy and un seize when given a small break once they are hot, at least the first time the symptom appears.
There was a recent thread where someone tried to fix the hydraulic unit. Not sure if it will help or not as I have never tried it, I have only done there first step and bought a complete unit and switched out the module to reuse the one that was in the car after testing it to make sure it is not a fault.


[SOLVED] Stuck ABS module valve - can it be rebuilt at home?
Hey sailor. Thanks for your reply.

Do you think a E60 dsc hydraulic will fit the E39?
I know the electronics dont.
 

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There are options when searching for just the hydraulic part, I just don't remember any of the details. I have not touched an M5 in a few years now, I am pretty much only doing things to RS4s now and not much of that, just old age, wrenching is not as much fun any more.
 

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Discussion Starter · #14 ·
There are options when searching for just the hydraulic part, I just don't remember any of the details. I have not touched an M5 in a few years now, I am pretty much only doing things to RS4s now and not much of that, just old age, wrenching is not as much fun any more.
Just pulled a 540i hydraulic and mated with my electronic bit of DSC. Worked like a charm. Apparently the mechanic never, ever saw this issue on any other E39's. He mostly fixes 530s and 540s.
Interestingly, on my way back home, I get multiple misfires and another heck from the M.


Cheers,
Gabe
 
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