No brakes!!! Gravel trap

[jonbarrett]

Had great day at Brands. First half of morning session all fine. Into pits for a 10-min break and back out. Brake into Druids and, nothing! Pedal hits floor, 360, car full of gravel. Marshall said I locked-up but I didn't agree.

First half of afternoon session fine. Into pits for 10-min break and back out. Check brakes before jopining circuit and pedal hit floor again.

I've never had this before and don't want to experience it again. Is this likely to be boiled fluid?

Having let the car cool down for 30-mins brakes seem fine. Drove home no problems.

Fluid level is OK.

[jammy_basturd]

Could be fluid boiling. Stopping for 10 minutes would leave your brakes with little cooling air travelling over them, allowing them to soak the heat, some/most of which would be transferred into the fluid.

Definitely no leaks though? Nothing getting past the master seals?

[jonbarrett]

Fluid is full, no leaks obvious.

[GreenV8S]

Sounds like you boiled the fluid to me. Sometimes you will get extra clues such as brake fluid blown out the top of the reservoir. Although they will often start working again once the fluid has cooled down and condensed, the fluid will never be the same afterwards and will need to be flushed through. Also check for heat damage to the pads and rotors while you're there.

[TT Tim]

At a guess, boiled the brake fluid.

Get it changed - soon!

Edited to add: When did you last get the fluid changed, brake fluid is hygroscopic (absorbes water). Water and brake fluid = bad news.

Tim

Edited by TT Tim on Wednesday 29th July 10:46

[ridds]

Definetly boiled fluid. It'll have lots of moisture in it. Do you use 5.1?

[Nefarious]

TT Tim said:

brake fluid is hydrascopic (absorbes water).

[Pedant]It's hygroscopic[/pedant]

Counter-inituitive, I know, but my mechanic chap picks me up on it every time I accidently say hydro...

[jesfirth]

i use Castrol SRF 600 - its boiling point is ridiculously high and it is expensive but despite the abuse my car gets it has never failed - if you take you car on track you should change the fluid at leat once a year - i do mine twice a year

[jonbarrett]

The fluid has not been changed since I bought the car three years ago. My insurance does limit me to 5,000 miles per year so I have probably done about 12,000 miles since I bought her. She was serviced just before I bought her but I don't know if the fluid was changed.

I do three or four track days a year.

I tend to change the oil before a track day but never considered a brake fluid change!

I'll change it now and replace when I do the engine oil. What is the best you can buy? I seem to recall that replacing brake fluid with a different type could cause problems if they mix.

[ridds]

Castro SRF or CL fluids are good.

I spent out on some funky 5.1 stuff once and it was full of water within 12 months.

I'd stick with 4.1 high temp.

[jonbarrett]

Thanks chaps, a flush and new fluid it is.

[TT Tim]

Nefarious said:

TT Tim said:

brake fluid is hydrascopic (absorbes water).

[Pedant]It's hygroscopic[/pedant]

Counter-inituitive, I know, but my mechanic chap picks me up on it every time I accidently say hydro...

Don't know what you mean, looks okay to me.

Tim

[Brummmie]

Ignore DOT ratings, go on fluid boiling point to see how robust your fluid will be trackdaying, 300C+ is where the good stuff is.

[GreenV8S]

jonbarrett said:

I do three or four track days a year.

I tend to change the oil before a track day but never considered a brake fluid change!

I'd say that was your problem.

You should flush the fluid any time it has been overheated, and also each time you change the pads. (I suspect you're getting through a fair few sets of pads if you're doing that many track days.)

[Omerta]

SRF is the undisputed daddy of brake fluids, but if the price makes your eyes water there are somewhat lesser but waaay cheaper options that would be fine for your road/track use.

There's a good article about brake fluids explaining DOT ratings, hygroscopic properties effects on boiling points, etc. here:

http://www.stoptech.com/tech_info/wp_brakefluid_1a...

[Omerta]

Brummmie said:

Ignore DOT ratings, go on fluid boiling point to see how robust your fluid will be trackdaying, 300C+ is where the good stuff is.

... and unless you're going to do a full bleed more than annually, pay more attention to the wet boiling points than the dry.

ETA: Brummie - what are the wet and dry specs for your stuff?

Edited by Omerta on Wednesday 29th July 23:00

[MackemPete]

I just put halfords high temp in mine. The specs are in the same league as more expensive stuff i.e. 300+ boiling point but the price is a lot less. Had no problems with the abuse i gave it at the ring.

I'm probably about to get slated for using halfords products

[Brummmie]

Omerta said:

Brummmie said:

Ignore DOT ratings, go on fluid boiling point to see how robust your fluid will be trackdaying, 300C+ is where the good stuff is.

... and unless you're going to do a full bleed more than annually, pay more attention to the wet boiling points than the dry.

ETA: Brummie - what are the wet and dry specs for your stuff?

Edited by Omerta on Wednesday 29th July 23:00

Info here.

http://www.carbonelorrainebraking.co.uk/fluid.html

[jesfirth]

chaps - IMHO the cost really irrelevant - think of the consequences if your brakes fail. the SRF 600 boils at yes youve guessed it above 600 degrees