Have a quick question for you more experience folks:

I think I may have boiled my brake fluid I am not quite sure what the symptoms are so I thought I would tell you guys what happened and see if what I describe makes sense…

I don’t think I have boiled fluid before, both the other cars I have track experience with are low hp <1,000lbs single-seaters that are easy on their brakes. One of the things I have be doing to try and get my times in the mini fast is compressing my breaking zones as I get more confident with the car. So the past weekend I was setting some personal bests, but when I came to stop I noticed smoke pouring off the front brakes (might have been occurring before but I hadn’t noticed fade per say) I couldn’t see the rears from the inside of the car. It was not an insignificant amount of smoke (at first I thought my head gasket was gone) and was sustained for a while before I decided to not be dumb and drive around for a while to cool them down. I was pleased with how the pads were performing though…

This was my first track time on these pads (Axxis ULT) only had some autoX that didn’t get them hot. Previously I had gotten some smoke using OEM pads on track and at MOTD but never quite this much (or while braking this late).

Anyhow, after all that I did some street driving in the same car yesterday and it feels like the pedal has slightly more travel than it did before to get the same amount of stopping power (just light street braking). I am sure you understand why this is a little concerning to me

Agree that is the fluid that went poof?

Parts are:
MINI OEM Fluid ~6-8months old)
Axxis ULT Pads (Stock Calipers, I would love to have track pads but I am still in school so budget is tiny lol)
Centric OEM Replacement rotors (put on new with the pads ~ 3 months ago)
Goodyear F1 GS-D3 205/45R16… at/beyond the wear bars now :-/
Lemme me know if any other information would be helpful

 

Did you pedal ever go soft during the run? I've boiled mine before and the pedal just went completely soft during the run and I would need to pump the brakes a couple of times to get some pedal back.

Street driving later felt exactly as you state, so it probably is the fluid. Decent brake fluid is pretty cheap so I would just go ahead and change it. Especially since you obviously track/autox your car every so often.

 

You most likely boiled the fluid and it will need a brake bleed at the minimum to restore the pedal feel. Before you go to the track again I'd recommend doing a complete flush with some proper high temp brake fluid such as Motul RBF600 or ATA Super Blue, both excellant fluids.

Since this is a heavier car than you are used to tracking a quick suggestion. At the end of a track session, try not to use the brakes to bring the car to a complete stop as this will leave the pads resting against the rotors and can warp them because they will not cool uniformly. Where the pads are touching the rotors they will not cool and the rotors will transfer heat to the calipers and brake fluid.

Try to bring the vehicle to a complete stop by just turning off the ignition and coasting to a stop without applying the brakes. This way the pads won't be touching the rotors as things cool off.

 

I would flush the fluid for sure...

Second, when the brakes are smoking hot, the last thing you want to do is come into the pits or paddock and hold them against the rotors, like Bilbo said. Otherwise, you'll get pad transfer. Use the brakes sparingly to get to your spot in the paddock and shut the car down with the clutch in, then let the clutch out to keep the car from rolling. Or, take a cool down drive (minimum 10 minutes, no stopping) and do the same. Do NOT set the e-brake for the same reason as above...

 

My pedal did get a tad softer, but I didn't have to pump the brakes to get them 'back' per say.

Yeah I know I should be using parts designed for what I do, but I try and destroy my stock parts first, last fluid change was a free dealership one lol.

How much would I need for a full flush? Assuming I don't spend 2 hours chasing bubbles looking for my rock hard pedal to return...

Luckily that was the last event I am doing this season, so I have lots to time to look around.

Yeah, I guess I hard a brain fart coming to a complete stop like that before cooling down I wasn't expected temps to be that much higher I guess, I should know better than to rest with the pads on the rotors. I do drastically cut speed to minimize braking on the last lap or 2. But I must admit to using the brakes to come to a complete stop after that short cool down...

I guess I should add some more cool down time as I get faster, I wish my car had as much telemetry as games like rFactor then I could see my rotors temps live while cooling down!

Thanks for the tips to help prevent me from putting on another smoke show!

Yeah I got smacked around, by some experienced folks, for using my e-brake instead of transmission to hold the car after fast running a year or two ago :-X so i got that part on lockdown

 

If you had new pads on old rotors, the smoke could have been old pad material embedded in the rotors getting burned off, otherwise the only way you could get smoke is burning the new pads or having a fluid leak, which should be obvious.

The last track event I did at HPT I noticed a definite "going away" of my pedal pressure, a couple of laps of much easier (and earlier) braking brought it back again, but next time I'll have ATA Blue in there (I was running stock street fluid)

Absent any leaks, I'd say new fluid at the minimum, and it might not hurt to have new rotors or those turned if they weren't new with the pads.

 

I did put new rotors on at the same new I put those pads on ~3months ago. I hope I didn't burn my pads. I am not familiar with this phenomenon. Would my pads be ruined? Can I tell by taking them off and looking at them?

I will also check around for leaks again, but I didn't notice any during my post event check.

Thanks for the help.

 

X2 for ATE BLUE. I haven't had fading brakes since I switched to it and I have the OEM brakes and pads. Then again I also added S/S lines at the same time.

 

You need at least 1L for a full flush...

 

Thanks, I think I will go ahead and do a full flush, 1L isn't that much unless it is Casterol SRF LOL. Any thing special I have to do going from 4.1 to 5.1? I have only worked on cars that started with 5.1 before, and have heard some funny things about mixing fluids, don't recall what types though...

 

Are you talking about the DOT spec? If so, Ate Blue or Typ 200 are both DOT 4... The MINI uses DOT 4. Other good choices are Motul RBF 600, Wilwood 570, etc. You do not want to use anything but DOT 4...

If you don't have a power bleeder (Motive Products makes a good one), you just add the fluid, pump and hold (or have someone else do it), crack the bleeder and run enough fluid through until you're confident it's flushed... Alternating between Ate Blue (which is actually blue) and Typ 200 (gold) is a super-easy way to tell if you have the system flushed. Just look for the color change! A power bleeder makes it uber easy to do this by yourself - my wife hates being the one who pumps the pedal.

Flush once, completely, then let the car sit 15 minutes. Then, flush again.

 

Yes, I was talking about the DOT spec. I just assumed when you guys were talking about track fluid it was DOT 5.1, oops my bad. I thought better=5.1. Good thing I asked! Also, I thought Motul RBF 600 was a 5.1? But I could be way wrong as I don't have a bottle infront of me.

Anyhow, yeah I have used the manual method before, but got a motive bleeder for the other car and it was a god-send. Think I will have to get one sized for the MINI aswell... Saves soooo much time and effort

Hadn't heard that 15min pause trick and the different coloured fluid sounds like a genius idea!

 

RBF 600 is DOT 4... Motul does make a 5.1, but you don't want that.

If you already have the Motive bleeder, you should just be able to order the kit that works for Euro cars and save some $!

 

Ahh oops! looks like i need to do a bit more learning/research about brake fluid types...

hmm quick google "Widely exceeds DOT 3, DOT4 and DOT 5.1 standards (except for DOT 5.1 viscosity at -40C)."
http://www.motorspotstore.com/morabrfl660.html

Those specs and your comments are starting to make a bit more sense now!

Thanks for all the help!

If only I had the cash for one of those BDM kits...
Maybe when I am older lol
i wish my r50 was as sweet as that one you guys run w/the getrag 6 and all...

 

All it takes is a lot of $ and hard work... lol... We did our's "on the cheap" by doing all the work ourselves and it was still expensive.

 

I've taken my pads out and scuffed them lightly with my belt sander - works really well if you've glazed your pads. Gives a nice fresh surface to bed in again and you don't have to take that much material off to clean them up so you really don't lose much mileage off them.................

 

Here's a how-to that I wrote for the Motive Power Bleeder on my MINI a few years back: http://www.metroplexmini.org/forum/s...r+instructions

 

PS: At my last track day, I pulled off of one session after 90% of the session was gone because of a tire issue. I didn't get the cool down lap like I usually did and noticed as the brakes were smoking once I held still long enough to ask the guys in the pit a question (foot was not on the brake). Heat transfers much better without the cool air rushing by, so while the brakes are very hot, keep moving!

 

haha yeah that money stuff always looking to hold me back with my annual car budget it will be a good chunk of years before I come close to being done LOL If only track days were free! Come to think of it... parts too! Though hopefully graduataition -> job -> more mini budget -> more fun

Ah yes, now that I think about it I remember doing a similar thing with some mountain bike hydraulic disk brake pads... after spilling brake fluid all over them, that was not a fun day pads don't work quite as well soaked in a lubricant like brake fluid... wonder why LOL

speaking of air flow that reminds me, my Heat Transfer exam is tomorrow!
One of the example questions is modeling the temperature of a 2 piece brake disc as the pad is applied and subsequent cooling (much much harder), seems kinda appropriate, i wish the brake pad covered the whole radius of the rotor would make the math tonnes easier LOL

ps thx for the link!