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Brake pedal to the floor after 4 laps. #1631686
14/04/2019 16:45
14/04/2019 16:45
Joined: Nov 2006
Posts: 1,563
Melbourne, Australia
Scuderia Offline OP
My life on the forum
Scuderia  Offline OP
My life on the forum

Joined: Nov 2006
Posts: 1,563
Melbourne, Australia
Took my Coupe to "The Bend", South Australia. What a fantastic facility! More to the point, brake pedal went to the floor after about 3-4 laps on my second run. My question is, can this be something other than the fluid? I haven't done anything different from the previous 4 track events, the only variable is the circuit, which I must admit is hard on brakes but still, it seems unlikely.

Brakes are standard Brembos with Winmax W5 race pads and super dot 4 brake fluid.

First time out I noticed the discs were glazed, noisy LF, a little vibration, nothing too concerning and good stopping power. I tip toed around for the first run learning the circuit, it was my first time out. I decided to try to push the brakes hard on the second run to see if they would come right - and they did, no noise or vibration, good stopping power so I then pushed on and set my fastest 2 laps and by the 3rd or 4th lap the pedal went to the floor all of a sudden. I still felt I was fairly easy on the brakes leaving a lot of margin.

It took 3-4 pumps to get any pedal and then when it came back it was very uneven, pulling to the left, even with the pedal very low the ABS was interrupting, I assume for one of the rears. Let the brakes cool, pedal came back, tried bleeding the brakes, no air. All seems fine again. 3rd run I took it easy for 3-4 laps without trouble, then a few hard laps the pedal went again, this time I continued slowly and the pedal came back up, basically if I was gentle on the brakes they were OK.

Any thoughts?

Re: Brake pedal to the floor after 4 laps. [Re: Scuderia] #1631687
14/04/2019 18:47
14/04/2019 18:47
Joined: Sep 2009
Posts: 4,640
ation
S
szkom Offline
Forum is my job
szkom  Offline
Forum is my job
S

Joined: Sep 2009
Posts: 4,640
ation
Sticky caliper. I had a road car something similar. Turned out the rear shoes were able to drag when hot which caused my fluid to boil.

Strip, clean, new fluid

Re: Brake pedal to the floor after 4 laps. [Re: Scuderia] #1631688
14/04/2019 19:29
14/04/2019 19:29
Joined: Jul 2007
Posts: 333
France
french_coupe Offline
Club member 773
french_coupe  Offline
Club member 773
Making a profit

Joined: Jul 2007
Posts: 333
France
Sounds like a fluid problem. Do you use high temp fluid and change it from time to time? If there was no air and no fluid loss then it cannot be anything else.


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Re: Brake pedal to the floor after 4 laps. [Re: Scuderia] #1631689
14/04/2019 20:28
14/04/2019 20:28
Joined: Oct 2008
Posts: 6,605
In the coupe.
magooagain Offline
Club Member 259
magooagain  Offline
Club Member 259
Forum is my life

Joined: Oct 2008
Posts: 6,605
In the coupe.
It's easy to boil standard brake fluid in a track scenario. High temp fluid is the only way to go.



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Re: Brake pedal to the floor after 4 laps. [Re: Scuderia] #1631697
15/04/2019 07:49
15/04/2019 07:49
Joined: Dec 2005
Posts: 17,122
Staffordshire
Nigel Offline
Club member 123
Nigel  Offline
Club member 123
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Joined: Dec 2005
Posts: 17,122
Staffordshire
How old is the Dot 4 fluid? It is hygroscopic, so you may have experienced the water content of the brake fluid boiling in the calipers, which will give the "pedal to the floor" effect.

Before changing any of the hardware, I'd try a fluid change. Make sure you use a top-quality fluid from a household name brand - eg Castrol SRF - there are lots of no-brand brake fluids that have a considerably lower heat range than some of the top-grade stuff


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Re: Brake pedal to the floor after 4 laps. [Re: Nigel] #1631699
15/04/2019 09:54
15/04/2019 09:54
Joined: Dec 2005
Posts: 436
Guildford
wink Offline
Club member 1453
wink  Offline
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Enjoying the ride

Joined: Dec 2005
Posts: 436
Guildford
Originally Posted by Nigel
How old is the Dot 4 fluid? It is hygroscopic, so you may have experienced the water content of the brake fluid boiling in the calipers, which will give the "pedal to the floor" effect.

Before changing any of the hardware, I'd try a fluid change. Make sure you use a top-quality fluid from a household name brand - eg Castrol SRF - there are lots of no-brand brake fluids that have a considerably lower heat range than some of the top-grade stuff


+1 old fluid boils at much reduced temperature

Re: Brake pedal to the floor after 4 laps. [Re: Scuderia] #1631704
15/04/2019 13:59
15/04/2019 13:59
Joined: Nov 2006
Posts: 1,563
Melbourne, Australia
Scuderia Offline OP
My life on the forum
Scuderia  Offline OP
My life on the forum

Joined: Nov 2006
Posts: 1,563
Melbourne, Australia
Thanks for the suggestions. I flushed the fluid prior to the event and I replace it yearly. I even flushed the clutch this time too. The clutch fluid was terrible too, I should probably flush it more often!

I've been using Castrol React Performance Dot 4 for the last 5+ years without issue. Boiling pt is 284C which is respectable for a dot 4, minimum is 260C.

SRF is 320C, will that make all the difference? I'm not so sure. I can try the fluid of course. Unfortunately that race track is 400 miles away so not easy to test it out!

Re: Brake pedal to the floor after 4 laps. [Re: Scuderia] #1631706
15/04/2019 15:20
15/04/2019 15:20
Joined: Jun 2007
Posts: 918
Carlisle
Rob40 Online content
Club Member 1717
Rob40  Online Content
Club Member 1717
Enjoying the ride

Joined: Jun 2007
Posts: 918
Carlisle
Are you using braided brake hoses? Old OE rubber ones can expand easily under heat and pressure.


This is how it should have come out of Torino!
Re: Brake pedal to the floor after 4 laps. [Re: Scuderia] #1631755
16/04/2019 19:46
16/04/2019 19:46
Joined: Oct 2010
Posts: 549
Bulgaria
Ferrarist Offline
Enjoying the ride
Ferrarist  Offline
Enjoying the ride

Joined: Oct 2010
Posts: 549
Bulgaria
Had similar situation 4-5 years ago........boiled brake fluid.....


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