Brake fluid on exterior of reservoir after DE event.

Several months ago when my dealer was replacing my defective clutch slave I had my hydraulic system flushed and filled to the FULL line with Ate Super Blue brake fluid. About two weeks ago, when prepping my Cayman S for a DE event, I inspected the brake fluid and noticed that the exterior of the reservoir was clean and dry and the that cap was secure. My brake fluid level was about 1/8" below the FULL line as one should expect due to the wear on the brake pads after several thousands of miles of daily driving. About ten days after the DE event I inspected the reservoir to see how much fluid lowering there was relative to the DE event's brake pad wear. The fluid was down about about an additional 1/16" which I believe is appropriate. I then noticed that the entire rim around the exterior of the reservoir had accumulated some Super Blue brake fluid. I know that most brake systems have a venting system engineered into the filler cap (some hidden better than others, I believe the CS vent is a labyrinth style that is integrated along the thread of the filler cap) to prevent a vacuum from forming as the pads wear and the fluid lowers. Could the G-force repeatedly generated after hard end of the straightaways braking cause the fluid to creep out of the vent? Could it have been forced out by pressure that may have built up in the reservoir as the heated fluid expanded due to a plugged vent then aerosol-ed out under the rapid release as the vent-way cleared? Any other possibilities? Any reports of a similar experience or explanations would be appreciated! Thanks, Joe

Were you following any BMWs too closely? In my opinion, the amount of fluid you're describing around the cap is totally inconsequential . I personally haven't witnessed any around my Cayman's reservoir, but my Corvette (Also equiped with ATE Super Blue and Goodridge lines) does show the same exact level of residue you mentioned, particularly after hard driving/track duty. Probably related to some combination of the viscosity of the fluid, G-forces, cap design, and possible aerosol/fluid aeration effect. Considering your fluid dropped by a 1/16 of an inch, easily attributable to pad wear (Does anyone else here actually take measurements or mark their fluid level?) I wouldn't be even slightly concerned. Maybe it's just me, but so long as the reservoir has some level of fluid in it, hasn't exploded, and my brake pedal works, I could care less about a little residue around the cap. In the hierarchy of car problems, this one comes in just after "slightly dim glove-box light".

Hello Alex, I appreciate your thoughtful albeit somewhat critical reply however I believe you misunderstood my post. I made no mention of any fluid accumulating around the cap but actually described that the "entire rim around the exterior of the reservoir had accumulated some Super Blue brake fluid". This fluid accumulation is not totally inconsequential and would be considered as a leak of some type by anyone that would see it. So if any readers would be kind enough to open the cover that allows access to their brake reservoir, regardless of if you've participated in a DE event or not, and report back if they to have found the same fluid accumulation, I would appreciate it. Thank you, Joe

Two days on the track in June with stock fluid and I didn't see anything like that afterwords. I have another DE weekend next weekend and I'll check again.

Thank you Pete, I keep watching for additional reports. Joe

The only time I saw brake fluid outside of the reservoir was after I accidentally spilled some while topping off the system. Otherwise, it's been dry. I frequently bleed the brakes, and have changed pads several times, so I would have noticed any leakage by now. Is it possible that you might have installed new brake pads without removing some fluid from the system prior to depressing the caliper pistons, thereby overflowing the reservoir? May I suggest you just bring it back to your dealership and let them have at it? If there's a leak, it would surely be covered under warranty.

Joe, This is only my second post but my first one was on a brake topic too. I must admit in your first post your were clear in your decription of the events but I assumed like Alex that you were talking about a minor amount of fluid aroud the cap. I first opened your topic because I read on the home page only the first words " Brake fluid on the exterior" and I thought let's see how this guy is going to fix that. I had a buddy that just had his Pantera painted and less than a month later that is what happened to him. I did not follow up to ask how he solved the problem because it was rather a sore subject to say the least. I have never used the Super Blue fluid why did you switch to Super Blue and did you notice a difference after.

Thank you Croc'ed, I'll be taking my CS to the dealership to have Cargraphic springs (-20 mm) installed and an alignment; I'll have them take a look over the brake reservoir. OPTIMUS, I changed to Super Blue in anticipation of some track use when my clutch slave was replaced. Thanks again Guys, Joe

Just checked my car because it was driven hard on a mountain run last week and thought I might add some useful info. The reservoir is very full, more than I would fill it, with fluid actually lapping the flat top surface. The dealer probably "topped it off" at my two-year service a few weeks ago. And there is NO fluid on the outside anywhere, bone dry.

Very unusual, I'd chalk it up to either a defective cap or a cap not as tight as perhaps it ought to have been.

Are you on stock tires? Are you on R compound tires? Not to keep denigrating your issue, but this is something not uncommon on cars capable of pulling much higher G forces than stock. (My dad's car actually flips the brake warning light on during hard cornering)

This has happened on my car. I thought it was because I boiled the fluid. Is it possible that is what happened to you?

Not likely... Superblue has a pretty high boiling point, the entire reason it's used is to prevent boiling.

Hi Guys, I want to apologize for my lousy memory but I just realized that the evening after my DE, I removed a wheel and retracted the pads/pistons to see if my pads were equipped with the stick-on anti-vibration spacing disks (they were). My reason for doing this was to see if I would be able to remove and reinstall my OEM pads if I would use Pagid Yellows for the track. I established that I was unable to remove the pads without damaging the spacing disks. As Croc'ed suggested, I'm now beginning to think that the pad/piston retraction done on the front right caliper may have overflowed the reservoir and spilled some fluid. Does anyone else think this would cause an overflow? Thank you, Joe

I'd say yes - I see no other reason for the cause --

D'oh! LOL, uh, yeah, that would definitely explain it. Can't say anything, I've had my share of Homer Simpson moments...

I ask the guys at Vision Motorsports about the brake fluid overflow issue. They report that it is quite common in track driven cars and said they wrap the reservoirs of the race cars with a rag and a rubber band to absorb the overflow. The technician then took me to a GT3 cup car in the shop and opened the trunk, revealing two red shop rags banded to the brake reservoirs. For the system to function properly the cap must vent and it is apparently possible for the fluid to find its way out of the reservoir under hard cornering, braking, etc. Cheers,

Hello AlexMcNabb, After reading Krokodil's post (thank you Krokodil!) I'm not convinced that the fluid displaced by retracting both pads in one (1) caliper would be enough to fill the remaining space above the fill line in the reservoir and spill over. When I do my next DE event I'll look to see if it happened again. Also, the next time I retract my pads, I'll keep an eye on the reservoir! Thank you all, Joe