Advice for leaked brake fluid from front lower caliper pin?
 

Hey all,



I recently returned from the track. This weekend while doing some maintenance, I noticed a small residue pool covered with dirt in the barrel of my Pass Front wheel.



After closer inspection, I noticed a dried dribble of yellow/orange fluid that appears to have come from the lower pin on the Pass Front brake caliper. There wasn't any other signs indicating that it could be motor oil or damper fluid.


The leak didn't appear to be continuous or ongoing as there was only a small pool on the wheel instead of a widespread spattering.


It may have occurred when I dropped the wheel off the track or caused by fluid boiling while the car sat in the paddock, as I got the brakes hot enough for them to be smoking. I didn't appear to have any issues on track or now with brake pressure. The caliper doesn't appear to be stuck either. The track was run CCW, so more stress on the passenger side is expected.



I'm going to continue to monitor for leaks and pull the pin to see if there are any issues. Would you all have any insight on what I should look for, precautions, or actions to take?


Thanks!


Standard 2 piston, Project Mu Club Racer Advance, Motul RBF 600

brembo's or standard dual-piston calipers?

i wipe it down, and keep a very close eye on both it and the fluid reservoir for the next few weeks.

yellow orange is an odd color for brake fluid unless it's contaminated-- it's also possible that some of the bearing grease in that front hub might have liquefied from the temps and the caliper was the lowest point to drip down off of.

Bearing grease is a good possibility. The residue on the wheel was pretty thick, way thicker than brake fluid would be, now that I think about it. And that could be why it didn't sling



I'll check the brake fluid reservoir. If I lost any it would be quite apparent

I'd probably flush that fluid if the brakes were hot enough to be smoking. You might also check to see if the pads are glazed.

Yeah I'll check. I'm not too concerned since they're track pads and fluid.

@gravitylover @soundman98


Pads seem fine. Fluid reservoir is a tiny bit lower than before track day, but I chalk that to pad wear.


Lucky for me, I broke a stud off in the process of swapping back to my street wheels. I took the chance to pulled the caliper out and take some pictures. See below for images.


I couldn't identify any clear grease trail from the wheel hub. Seems pretty localized to the caliper pistons and lower caliper pin. It might be the rubber grease from inside the caliper pin.



https://i.imgur.com/YBP9VVT.jpg


https://i.imgur.com/1U6mg1S.jpg


https://i.imgur.com/Y8YwkDp.jpg


https://i.imgur.com/H3SUyra.jpg


https://i.imgur.com/NNJ5npT.jpg


https://i.imgur.com/JDdt6r6.jpg


https://i.imgur.com/rdsH5sS.jpg


https://i.imgur.com/6LtibBa.jpg

Car is 100% fucked.
Burn car, it's not worth fixing at all.
Should have bought a better car.













Joking aside, simple answer is your brakes cooked the grease to its melting point, thus flowing the path of lest resistance and just oozed out a bit.
If it makes you feel better buy new boots and re lube those pins.

It is likely to be rust from a wet rotor transferring to the pad and dripping down on the rack.

Btw, the rust on the hub is horrific. Wheel hubs should be spotlessly clean and receive a thin coat of high temp grease to prevent rust from setting back in (I like either lithium grease or the permatex silicon-ceramic orange stuff, gray anti-seize goes on too thick and dries out too fast). Rust scales on a hub almost always put you out of spec for lateral runout on the rotor and are a frequent cause of wheel tightening issues.

But you have more pressing issues: one of the piston dust boots visible in your pic seems torn, and the friction material on the pad turning white is a sign the pad is being massively overheated, I usually see pads that color when I service neglected brakes that are totally seized. The fingers on the outer side of the caliper are also starting to change color, there is way too much heat being put into these brakes.

The rust could certainly explain the color. However, I think it's more than just water runoff here. I live in a very dry area (High Desert of Southern California), and the residue was for sure oily. If it were just water run-off, it would be dry and flaky like the rest of the components.

Thanks for that. I clean the hubs with wire brush and put antiseize on them when I can. The rust is unavoidable simply due to heat and enclosed environment. Wheel cleaner probably doesn't help either. I'll try a thicker grease and perhaps touch up with primer.

These see the track regularly, and that's the price to be paid. My pads (race pads meant to see the heat) always get their lettering seared off after the first outing. My friends were reporting the rotors were glowing faint red in the day time. The piston boots will never survive in that kind of environment. The pads work fine and still bite like they were new. There isn't anything more I can really do to help that other than take longer time cooling the car down and add temperature monitoring tape

Well if that is the case, you're probably melting the slide pin grease.

Maybe you should look into some brake cooling ducts because they're definitely not having fun being heated like that.

yeah, the piston boots are definitely starting to crack, a piston leak isn't that far into your future.

if your'e tracking the car consistently, track-spec calipers would definitely be a worthwhile cost.

Since the calipers have yet to actually fail, it's probably more economical to rebuild them: Piston seals and boots can be had for a very low cost, and while they're torn down, it would be a good opportunity for high temp paint to protect them, then going forwards, this seems like the exact thing that would be needed.

http://www.ft86speedfactory.com/velo...l#.XWPOinVKiUk

^
I agree
It looks like your cooked the grease in the guide pins. Or possible your bleeder valve was not torqued to spec?
I would make sure the guide pins can freely move, then make sure they are greased properly (with the right silicon based grease), clean the boots and make sure no damage is there. Also take out the guide pins and inspect those for any signs of wear or damage.


They don't look too bad to me. Are you talking about the piston boots or the guide pin boot?

I pulled both top and bottom pins, cleaned them, and put new OE rubber grease. Pins themselves looked okay. The lower rubber guide bushing was fraying, so I replaced it.

I think they are talking about the caliper piston boots.

Ordered some GT3 brake ducts to help with the cooling