I keep boiling brake fluid

[hostler]

For some reason (I think) I keep boiling my brake fluid. I can't really get my head around it. I've changed brake fluid plenty of times now and tried a few different ones. Latest one was Motul RBF600 but after 4 20 minute sessions on track (Assen) the pedal has gone soft again. There sessions had about 35 minutes in between them except for the last two.

I am using stock calipers with HEL braided hoses, Brembo HC discs and Carbone Lorraine RC6 pads in front. Brembo pads and OEM discs in the rear. I have brake cooling (without a deflector plate). It's a phase 1 172 with ABS.

I find the ABS system kicking in really late as well. When the brakes get hot I can brake as hard as I want but the ABS system is not doing much. It doesn't lock up the wheels though so that's good.

I'm thinking there's either something wrong with me (the driver) or a fault in the ABS system. I do brake quite late and hard. Also, Assen is quite demanding on the brakes but looking at the brake discs, pads, fluid and cooling you'd think I'd be fine.

I've read something about the ABS pump and it being hard to bleed properly but I doubt there's any air in it because just after changing over the brake fluid the pedal feels really good.

Has anyone ever experienced this? I'm moving to 4 pots brembo's soon but this might make it worse.

 

[JamesBryan]

RBF600 doesn't have that high of a wet boiling point tbh.

Try Castrol SRF, it's expensive but it has the highest wet boiling point of pretty much all the fluids around.

If the pedal is quite long then you also have air. You'll need to activate the abs pump whilst bleeding using Clip or the RSTuner ABS module.

 

[JB21]

Could just be the callipers sticking slightly creating more heat. Also is your brake fluid header open without any insulation between the manifold as this creates massive heat soak.

I've never once boiled even standard fluid on my 182 with all sorts of pads (DS2500, DS3000, DS1.11, CL5+, CL8, M1155) all coupled to HC discs, and like yourself I brake very late and hard at hard on the brakes tracks like Blyton even in hot weather so does sound like there's an issue somewhere.

 

[Scrooge]

If it’s not locking up then there’s no need for the ABS to kick in, the sensors pick up that wheel has locked then ABS kicks in to correct which wheel is causing the issue

 

[Knuckles]

Sounds like a sticky calliper to me

 

[hostler]

RBF600 doesn't have that high of a wet boiling point tbh.
Try Castrol SRF, it's expensive but it has the highest wet boiling point of pretty much all the fluids around.
If the pedal is quite long then you also have air. You'll need to activate the abs pump whilst bleeding using Clip or the RSTuner ABS module.

But if there would be air in the system this would cause the pedal to be soft all the time and not just after a trackday?

Thanks for the tip about activating the ABS pump. I don't have a clip but this is very useful.

Could just be the callipers sticking slightly creating more heat. Also is your brake fluid header open without any insulation between the manifold as this creates massive heat soak.

Good point about the caliper maybe sticking. I haven't noticed excessive wear on one side though but it's worth investigating further. I'll most likely not be doing any trackdays untill the Brembo 197 calipers are on so not worth rebuilding these.

Not sure what you mean with the insulation? The standard stuff on the bulkhead has all been removed. I forgot to mention this is a RHD car so the booster etc sits behind the battery.

Sounds like a sticky calliper to me

For some reason I didnt think about this. I recently replaced the pads and the pistons moved freely. Also cleaned and greased the sliders with some stuff (its white) that is more heat resistant than copper grease.

 

[Vaughan]

What's your braking technique? Short and hard is better than long and soft because it gives time for heat to dissipate.

Every time you go to brake, pause and think wehether you really need to. If you do need to brake you've waited a bit so brake harder for shorter time.

Little dabs on the brakes do little but heat them up and keep them hot. The longer they are hot the more heat conducts to the brake fluid.

Regarding your brake cooling: are you sure it's effective? I've been doing some reading on aero and cooling for intercoolers and brakse and it's common to make things worse.

Here is a link to somebody who added a bonnet scoop above their intercooler and found it didn't work as well as expected. They scienced-the-f**k out of it with differential pressure gauge measurements and discovered that at road speeds the scoop was sucking heated air out of the engine bay through the intercooler and out the boonet scoop -- making it worse. They fixed it with an under-bumper tray to control air flow and lower the pressure under the engine.

Part 1: http://www.autospeed.com/cms/article.html?&A=113176
Part 2: http://www.autospeed.com/cms/article.html?&A=113177

 

[JamesBryan]

One thing you'll notice with the 197 Brembo's is that the pedal travel will be longer.

I've heard that from a few people who have them. Nothing too major though.

 

[car.crash]

What sort of brake cooling are you using?

 

[Sam the man]

RBF600 doesn't have that high of a wet boiling point tbh.

Try Castrol SRF, it's expensive but it has the highest wet boiling point of pretty much all the fluids around.

If the pedal is quite long then you also have air. You'll need to activate the abs pump whilst bleeding using Clip or the RSTuner ABS module.

REACT Performance DOT 4 is a better compromise. I have used this on my VX220 turbo racing and never once boiled. unless you are racing a very heavy car with huge breaking loads SRF is not necessary