# Brake Pedal drops to the floor after exiting track ..............



## 91 a2vr (Jun 13, 2002)

Here's a bit of a background on my old Mk2. I've had it for 15 years and never tracked it. I drive the car no more than 5,000km per year for the last 10 years. I did a vr6 conversion on it 8 years ago. The front brakes were upgraded to Corrado VR6 calipers and rotors (running Hawk HPplus pads) but I've left the rear stock drums.
I took the car out yesterday and spent the afternoon lapping it. After completing about 6 laps of complete abuse I would get off the track & park the car to let it cool off. The brakes felt fine during the race but within 5 minutes of exiting the track my brake pedal would get spungee and go to the floor before I had any brakes. I let the car sit for about 40 minutes and then I would start to regain brakes again. 
What would cause this ????? Is it possible that I boiled the stock brake fluid which I changed 4 years ago??? And if so, what brake fluid do you guys recommend I use if I decide to continue tracking the car.
Thanks.









_Modified by 91 a2vr at 2:08 PM 8-17-2009_

_Modified by 91 a2vr at 2:09 PM 8-17-2009_


_Modified by 91 a2vr at 2:14 PM 8-17-2009_


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## greyhare (Dec 24, 2003)

*Re: Brake Pedal drops to the floor after exiting track .............. (91 a2vr)*

Are you doing a cool down lap?
From your description the fluid in the calipers is boiling from heat soak.
Four years is too long; the brake fluid should be flushed every two years minimum.


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## GTijoejoe (Oct 6, 2001)

*Re: Brake Pedal drops to the floor after exiting track .............. (greyhare)*

Sounds like you are exceeding the boiling point of the fluid.
I would suggest Motul 600... forget that superblue crap, it has been known to develop problems in OEM brake systems and stain basically everything.... many ppl ignorantly swear by it, and some ppl have had really good experience with it.


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## 91 a2vr (Jun 13, 2002)

*Re: Brake Pedal drops to the floor after exiting track .............. (GTijoejoe)*


_Quote, originally posted by *GTijoejoe* »_Sounds like you are exceeding the boiling point of the fluid.
I would suggest Motul 600... forget that superblue crap, it has been known to develop problems in OEM brake systems and stain basically everything.... many ppl ignorantly swear by it, and some ppl have had really good experience with it. 

Thanks for the info. Have you heard anything about the Ford Heavy Duty brake fluid. I happen to mention my problem to a co-worker of mine and he says he has heard of people using that stuff for racing application. Any ideas????


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## greyhare (Dec 24, 2003)

*Re: Brake Pedal drops to the floor after exiting track .............. (91 a2vr)*

I have had good results with the Motul RBF 600. Dry/wet boiling points 593F/420F.
http://www.stealth316.com/2-brakefluid.htm
From the linked article.

_Quote »_Ford Heavy Duty brake fluid is cheap ($6/liter) and has a very-high dry boiling point, making it a favorite for the weekend racer that changes brake fluid frequently. However, the DOT 3-rated wet boiling point makes Ford Heavy Duty less than desirable for street usage.


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## GTijoejoe (Oct 6, 2001)

*Re: Brake Pedal drops to the floor after exiting track .............. (91 a2vr)*

As stated, it really depends on the boil point rating of the actual fluid. DOT3 and 4 are just regulated specs, the actual fluid specs can be greater.... it just depends. 
You can use the heavy duty fluid no problem, basically you'll have to change it frequently so the wet boiling point doesn't sneak up on ya in the long run with driving on the track. 
I'll tell you a secret about brake fluid, you actually never need to change it, but it is not the smartest idea. It will reach the saturation point of absorbing water, and corrosion is inevitable in a brake system which leads to build up and system failures, the compressability of the fluid over time will get worse, but it will still work....poorly....so <$10/liter why wouldn't you change it


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## Urbanfundamentalist (Aug 21, 2009)

*Re: Brake Pedal drops to the floor after exiting track .............. (91 a2vr)*

Probably two problems. 
Your 4 year old brake fluid is 4 years old, and you probably need a longer cool down period.
Given that you were lapping fine, it sounds like your fluid was in decent shape, for which you are very lucky. 
VW recomends changing the brake fluid every 2 years on a street car. When I was autocrossing I would change my fluid a minimum of every year, more frequently depending how much track time the car saw. If you are doing frequent track days, you may need to replace it more than once a season. Either way 4 years is way too long with or without track days (even if the fluid doesn't boil, it's absorbing moisture and rotting the lines from the inside). 
I've had great luck with Castrol GTLMA (Low Moisture Activity). I'd advise against race fluid if this car is also your daiy driver. Typically (but not always) race fluid has a super high dry boiling point, but a much lower wet boiling point, and it's usually not designed to resist moisture absorption (why ATE superblue gets a bad rep, works fine if you change it frequently). Essentially it's intended to be replaced frequently (like before every race weekend) and therefore doesn't have to stand up to the time, bad weather, and heat cycling of a daily driver. 



_Modified by Urbanfundamentalist at 10:37 PM 8-20-2009_


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## lonepatrone (Jan 22, 2005)

*Re: Brake Pedal drops to the floor after exiting track .............. (GTijoejoe)*


_Quote, originally posted by *GTijoejoe* »_As stated, it really depends on the boil point rating of the actual fluid. DOT3 and 4 are just regulated specs, the actual fluid specs can be greater.... it just depends. 
You can use the heavy duty fluid no problem, basically you'll have to change it frequently so the wet boiling point doesn't sneak up on ya in the long run with driving on the track. 
I'll tell you a secret about brake fluid, you actually never need to change it, but it is not the smartest idea. It will reach the saturation point of absorbing water, and corrosion is inevitable in a brake system which leads to build up and system failures, the compressability of the fluid over time will get worse, but it will still work....poorly....so <$10/liter why wouldn't you change it









_Quote, originally posted by *GTijoejoe* »_As stated, it really depends on the boil point rating of the actual fluid. DOT3 and 4 are just regulated specs, the actual fluid specs can be greater.... it just depends. 
You can use the heavy duty fluid no problem, basically you'll have to change it frequently so the wet boiling point doesn't sneak up on ya in the long run with driving on the track. 
I'll tell you a secret about brake fluid, you actually never need to change it, but it is not the smartest idea. It will reach the saturation point of absorbing water, and corrosion is inevitable in a brake system which leads to build up and system failures, the compressability of the fluid over time will get worse, but it will still work....poorly....so <$10/liter why wouldn't you change it









I disagree with your statement about never needing to change brake fluid. If you track a car the heat exposure to the fluid allows it to better absorb water, which lowers the boiling point more quickly down to the wet point temperature rating of the fluid. I just came back from the track today, and when I measured my rotor temps on the front I was at 400 degrees and around 350 in the rear. I know I was closer to 600 degrees at the rotor at the end of my braking zone. 
Long story short, if you go to the track put in fresh high temp brake fluid and upgrade your pads to a more aggressive pad. It's the only way to enjoy time at the track.


_Modified by lonepatrone at 6:48 PM 8-23-2009_


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## GTijoejoe (Oct 6, 2001)

*Re: Brake Pedal drops to the floor after exiting track .............. (lonepatrone)*


_Quote, originally posted by *lonepatrone* »_
I disagree with your statement about never needing to change brake fluid. If you track a car the heat exposure to the fluid allows it to better absorb water, which lowers the boiling point more quickly down to the wet point temperature rating of the fluid. I just came back from the track today, and when I measured my rotor temps on the front I was at 400 degrees and around 350 in the rear. I know I was closer to 600 degrees at the rotor at the end of my braking zone. 
Long story short, if you go to the track put in fresh high temp brake fluid and upgrade your pads to a more aggressive pad. It's the only way to enjoy time at the track.

_Modified by lonepatrone at 6:48 PM 8-23-2009_

Your statement is true, but I think my point was taken incorrectly. The fluid acting obviously as a hydro fluid will still work. There are downsides to not changing the fluid, and my point was never intended or pointed towards a vehicle that will see track braking events... it was just general knowledge..... and like I stated I would never recommend never changing your fluid.... does that make sense








Case in point: The Mits dealership some how forgot to put my brake resevoir cap back on after replacing my FR calipers on my Evo, I drove ~400 miles over 2 months before I noticed (last saturday).... Wed. they will replace my cap, and I am forcing them to flush the fluid from it prematurely absorbing water with no cap.
Change your fluid regularly http://****************.com/smile/emthup.gif


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## 91 a2vr (Jun 13, 2002)

*Re: Brake Pedal drops to the floor after exiting track .............. (91 a2vr)*

thanks everyone for your info. I came a cross a good deal and bought some Motul 600. Hope this stuff works for me.
Cheers.


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## chois (May 12, 2000)

also consider providing additional air flow to the front brakes


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