Hello all,

I haven't got a chance to talk to my local MINI mechanics, but I wonder if any of you have this problem. When I open the hood and look at the break fluid tank, I almost always see small amount of yellow break fluid spilled over the tank. I usually wipe it off, but a week later or so, it's there again. I unscrew the cap and put it back on, and no change...

The causes I can think of:
1. Defective cap?
2. Defective tank?
3. bad break fluid???

I do autocross on weekends, and I do "spirited driving" around the city on weekdays as well. I wonder if I can resolve the problem if I bleed the break fluid (for better one) like Randy suggested. Am I pushing my MINI too hard?

Sorry, it's not really a mod question, but I value everyone's expertise on this forum the most. Thanks in advance.

 

Kazu,
I think when you do Autocross you are using your brakes alot and boiling the brake fluid so that it leaks out of the top of the brake fluid reservoir.

So change the brake fluid to something with a higher boiling point. ATE Super blue or go to RandyBMC's site.
Did you change the brake pads yet?
Have you noticed brake fade? Usually due to boiling fluid and overheated brakes.

Here is a test. At the beginning of the day of Autocross clean off the brake fluid reservoir. Then after each run raise the bonnet to cool everything and look at the reservoir and check for leaks. Should not be hard to find one.

 

>>Here is a test. At the beginning of the day of Autocross clean off the brake fluid reservoir. Then after each run raise the bonnet to cool everything and look at the reservoir and check for leaks. Should not be hard to find one.

Thanks!

Good point. I'll try it this sunday.

By the way, I guess I should have post this thread in "beneath the bonnet" forum. I just realized right after I clicked on "submit." Sorry!

Kazu.

 

I don't think that the brakes can get hot enough to boil the fluid at an autocross. It takes a lot of long, hard use to boil fluid, like at a track/driver's ed event. It's more likely that you are sloshing the fluid arond in the tank and the cap is leaky.

 

>>I don't think that the brakes can get hot enough to boil the fluid at an autocross. It takes a lot of long, hard use to boil fluid, like at a track/driver's ed event. It's more likely that you are sloshing the fluid arond in the tank and the cap is leaky.

This is a good point. Track sessions that last for 20 minutes each time are much more likely to cause brakes to overheat and for brake fluid to boil. To check for a cap leak you can start off you regular day and clean the brake fluid area then when you get to your destination check for any leak. If none then wait till the end of the day and check for a leak. If you detect a leak then take it to your dealer and have them check it.

I was on the track one day two sessions and I boiled my brake fluid as did several other MINI owners. I didn't really feel the brake fade was that bad but it was there a little. When I took in my MINI to the dealership they said that because I had lowered the suspension the people that did that install might have caused the brake fluid to spill out of the brake fluid container.

These days I have the better brake fluid better pads and rotors.

Under normal use the brake fluid should not be going outside the cap area.

 

When I took in my MINI to the dealership they said that because I had lowered the suspension the people that did that install might have caused the brake fluid to spill out of the brake fluid container.

Yeah right, and the stickers on your car cause flat tires.

 

Every MCS I've EVER seen has this leakage or "sweating" around the cap of the fluid reservoir. Something I've noticed is that the threads have a slit in them and the fluid seems to slowing come out of that slit. At a track event yesterday all cars seems to have this problem including mine, I'm running AP Racing brake fluid and Ferodo DS-2500 brake pads on my car and know for a fact that I didn't boil the fluid. I've noticed this at autocross events as well as just looking under the hood of an MCS.

Can someone who has NEVER tracked or autocrossed their car take a look at their fluid reservoir, I'm pretty sure you'll see the same thing.

Cheers,

Paul

 

Paul, how can you "know for a fact" that you aren't boiling your fluid? I had never had a "sweaty" brake fluid reservoir until last week at the track, when I'm pretty sure I was boiling my fluid....

 

>>Paul, how can you "know for a fact" that you aren't boiling your fluid? I had never had a "sweaty" brake fluid reservoir until last week at the track, when I'm pretty sure I was boiling my fluid....

"Know for a fact" might have been a little strong but I've seen this on SOOO many MINIs that just about every MINI in existance would have to be boiling their brakes for this to be caused by boiling fluid. I know that my brake feel didn't change on track last Sunday at all and had the fluid boiled I would have felt at least a slight feel change if not all out brake fade. Didn't experience even a minor change in feel to the brakes. The Ferodo DS2500s I'm running and the semi-fresh AP Racing brake fluid that is less than 2 months old ran great!

Second, I've seen this leaking on multiple MINIs even at autocross events and I can assure you that unless you've got the worlds fastest solo2 event you'd be hard pressed to boil even stock fluid in a run that takes 60 seconds.

Finally there is that "slit." The reservoir doesn't look to completely seal so I believe in the course of driving, especially spirited driving the fluid finds it's way out the slit.

Try this, wipe your fluid bottle dry and check it in a few days. If you see fluid after normal street driving you can be pretty damn sure it wasn't caused by boiling fluid.

Cheers,

Paul

 

Good idea--I like experiments! I too find it very hard to believe that even the most spirited of AutoX driving could boil fluid. I would think that hard street driving (lots of quick starts and hard braking) could be even more detrimental to braking than your average AutoX...but what do I know? While running stock pads, rotors and fluid, I definitely felt fading on my faster runs, especially toward the last lap or two (20 minutes sessions)--the car just wasn't responding as well to braking at speed...I'm sure it was a combination of pads and fluid, though it could have been pads only...I dunno. I noticed quite a bit of fluid outside the reservoir, and I hadn't noticed it on my first two runs (reasonably low speed with much more moderate braking).

Cheers!

 

I autocrossed this w/e and either sloshed or boiled some out. Maybe will change fluid since I did get hard on brakes a lot. Didn't lose braking but maybe they got hot. Never hit ABS limits before the w/e, but now know what it feels like. Esp. braking in a turn.

BTW, when I frequented the E30M3 board on roadfly, someone mentioned using the following brake fluid:

Ford Part No. C6AZ-19542-AA (DOT3HD - 550deg. boiling pt.
Supposed to have been necessitated by hi brake tems in a ford truck. Anyone know about that?

It's probably lots cheaper than the european stuff. Don't know adv/disadv or how they compare.

 

it's the cap leaking because i had the same problem before.