Did my brake fluid overheat?

TheMidnightNarwhal · 02-08-2020, 04:08 PM

I was drifting last night and throwing the car around in the snow and after my last donuts I parked it the clutch pedal wouldn't go back up.

So at first thought my slave or something like that broke and leaked. Fluid level looked ok.

I let the car idle a bit and after that all was working fine.

My questions are what exactly happened? What component did overheat to make it act like this? Because clearly nothing is actually broken right if all works now. My brakes also were working fine when issue occurs and still are. If the fluid was overheated wouldn't the brakes be full of air? Or could the fluid have heated up enough only maybe in the lines near the transmission to cause issues to clutch component but not to brakes?

TheMidnightNarwhal · 02-09-2020, 09:16 PM

I threw the car again tonight in a parking lot and similar issues. I wasn't even that hard on it.

Got a DCS (or ABS I think, yellow park light warning) warning disabled and also FTM error and my clutch pedal was starting to feel pretty stiff.

Is my clutch just over heating or what is over heating? Again, car feel perfectly good after wards of sitting.

Volasko · 02-10-2020, 12:29 PM

It doesn't make sense that the boiled brake fluid would anywhere close to the clutch line. Typically the fluid would boil in the caliper first. You'd have straight up set your car on fire for that temp to make its way back clutch line fluid. I'm a bit perplexed to the cause of the issue too, just thought I would throw in my 2 cents worth.

TheMidnightNarwhal · 02-10-2020, 01:19 PM

Quote:

Originally Posted by Volasko

It doesn't make sense that the boiled brake fluid would anywhere close to the clutch line. Typically the fluid would boil in the caliper first. You'd have straight up set your car on fire for that temp to make its way back clutch line fluid. I'm a bit perplexed to the cause of the issue too, just thought I would throw in my 2 cents worth.

Right? Having a hard time to thinking fluid over heated.

Other thing is maybe there is air in the clutch lines? But then again, how would that heat up in the first place. I'm not using my brakes when doing a donut or drift in snow.

bbnks2 · 02-10-2020, 01:25 PM

Quote:

Originally Posted by TheMidnightNarwhal

Right? Having a hard time to thinking fluid over heated.

Other thing is maybe there is air in the clutch lines? But then again, how would that heat up in the first place. I'm not using my brakes when doing a donut or drift in snow.

Air in the line doesn't have to come from heat. Bleed the slave and see if it happens again. Top off the brake fluid.

When drifting around it's possible the master cylinder sucked in some air from the fluid sloshing around in the reservoir. Same issue with oil in your sump and power steering fluideven. Fluids can cavitate and then be pumped through systems.

It's possible this could be the issue or a master/slave pulling in air. I'd think you would have external leak too though if that were case. You can cheat behind the clutch pedal for wetness.

TheMidnightNarwhal · 02-10-2020, 01:28 PM

Quote:

Originally Posted by bbnks2

Air in the line doesn't have to come from heat. Bleed the slave and see if it happens again. Top off the brake fluid.

When drifting around it's possible the master cylinder sucked in some air from the fluid sloshing around in the reservoir. Same issue with oil in your sump and power steering fluideven. Fluids can cavitate and then be pumped through systems.

It's possible this could be the issue or a master/slave pulling in air. I'd think you would have external leak too though if that were case. You can cheat behind the clutch pedal for wetness.

Yeah I never did bleed my clutch fluid originally when I did brake since it seems like such a PITA to do but now wouldn't be a bad idea with these issues.

If air was indeed sucked in, wouldn't my pedal not return to normal behavior though? Clutch or brake wise?

Tambohamilton · 02-10-2020, 01:30 PM

Nothing in the brakes affects the clutch, if the fluid level is good.

I'm guessing you'll be needing a new clutch release bearing soon, or something in that area.

bbnks2 · 02-10-2020, 01:30 PM

Quote:

Originally Posted by TheMidnightNarwhal

Yeah I never did bleed my clutch fluid originally when I did brake since it seems like such a PITA to do but now wouldn't be a bad idea with these issues.

If air was indeed sucked in, wouldn't my pedal not return to normal behavior though? Clutch or brake wise?

not necessarily

bleeding the clutch is the first place to start no matter what.

Antetokounmpo · 02-10-2020, 02:16 PM

Quote:

Originally Posted by TheMidnightNarwhal

Right? Having a hard time to thinking fluid over heated.

Other thing is maybe there is air in the clutch lines? But then again, how would that heat up in the first place. I'm not using my brakes when doing a donut or drift in snow.

I'm fairly certain the car is constantly applying brakes when drifting for the ediff, at least in my xi it smells like hot brakes when I finishing messing around in the snow, and I don't use the clutch obviously.

Tambohamilton · 02-10-2020, 02:37 PM

Quote:

Originally Posted by bbnks2

not necessarily

bleeding the clutch is the first place to start no matter what.

Sure, it won't hurt anything!

Yep, the e-diff will be working hard when doing that, and putting heat into the rear brakes. I just can't see that affecting the clutch unless the reservoir is sealed. Could be wrong though, as ever!

TheMidnightNarwhal · 02-10-2020, 03:34 PM

Quote:

Originally Posted by Antetokounmpo

I'm fairly certain the car is constantly applying brakes when drifting for the ediff, at least in my xi it smells like hot brakes when I finishing messing around in the snow, and I don't use the clutch obviously.

Quote:

Originally Posted by Tambohamilton

Sure, it won't hurt anything!

Yep, the e-diff will be working hard when doing that, and putting heat into the rear brakes. I just can't see that affecting the clutch unless the reservoir is sealed. Could be wrong though, as ever!

Ohhhhhh shit you guys are right I forgot about that. It still works when traction is off. That explains the brake error I got.

But yeah the clutch pedal remains a mystery.

feuer · 02-11-2020, 11:14 PM

Quote:

Originally Posted by TheMidnightNarwhal

Ohhhhhh shit you guys are right I forgot about that. It still works when traction is off. That explains the brake error I got.

But yeah the clutch pedal remains a mystery.

Slave cylinder. Is plastic. Gets hot from engine and transmission. Brake error is from rear wheels spinning lot faster than front. Nothing with brakes. All cars get these on dyno runs.

TheMidnightNarwhal · 02-12-2020, 12:51 PM

Quote:

Originally Posted by feuer

Slave cylinder. Is plastic. Gets hot from engine and transmission. Brake error is from rear wheels spinning lot faster than front. Nothing with brakes. All cars get these on dyno runs.

So all is fine. Fluid is still good?

feuer · 02-12-2020, 01:55 PM

Quote:

Originally Posted by TheMidnightNarwhal

So all is fine. Fluid is still good?

Probably you have failing clutch slave cylinder.

02-08-2020, 04:08 PM	#1
TheMidnightNarwhal Major General 2657 Rep 6,289 Posts Drives: 11' 335is DCT Join Date: Jun 2015 Location: Gatineau, Quebec iTrader: (0)	Did my brake fluid overheat? I was drifting last night and throwing the car around in the snow and after my last donuts I parked it the clutch pedal wouldn't go back up. So at first thought my slave or something like that broke and leaked. Fluid level looked ok. I let the car idle a bit and after that all was working fine. My questions are what exactly happened? What component did overheat to make it act like this? Because clearly nothing is actually broken right if all works now. My brakes also were working fine when issue occurs and still are. If the fluid was overheated wouldn't the brakes be full of air? Or could the fluid have heated up enough only maybe in the lines near the transmission to cause issues to clutch component but not to brakes?
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02-09-2020, 09:16 PM	#2
TheMidnightNarwhal Major General 2657 Rep 6,289 Posts Drives: 11' 335is DCT Join Date: Jun 2015 Location: Gatineau, Quebec iTrader: (0)	I threw the car again tonight in a parking lot and similar issues. I wasn't even that hard on it. Got a DCS (or ABS I think, yellow park light warning) warning disabled and also FTM error and my clutch pedal was starting to feel pretty stiff. Is my clutch just over heating or what is over heating? Again, car feel perfectly good after wards of sitting.
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02-10-2020, 12:29 PM	#3
Volasko Colonel 705 Rep 2,605 Posts Drives: 06 330i E90, 18 530xe G30 Join Date: Dec 2010 Location: Toronto iTrader: (2) Garage List 2018 BMW 530e M Sport [9.00] 2006 BMW E90 330i [8.28]	It doesn't make sense that the boiled brake fluid would anywhere close to the clutch line. Typically the fluid would boil in the caliper first. You'd have straight up set your car on fire for that temp to make its way back clutch line fluid. I'm a bit perplexed to the cause of the issue too, just thought I would throw in my 2 cents worth.
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02-10-2020, 01:30 PM	#7
Tambohamilton Brigadier General 3058 Rep 3,909 Posts Drives: E91 330d Join Date: Apr 2019 Location: Herefordshire iTrader: (0)	Nothing in the brakes affects the clutch, if the fluid level is good. I'm guessing you'll be needing a new clutch release bearing soon, or something in that area.
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