[dvas]

I've noticed during track days, that I sometimes have a few drops of clear fluid hitting my driver's side windshield, usually just after some hard braking. It seems to be coming from under the hood and, more specifically, from the brake fluid reservoir area, leading to the obvious conclusion that it's brake fluid.

This has occurred on 3 occasions out of 10 or so days this year. It always seems to happen in the first morning session only, going away by session 2 and not occurring again throughout the day. It doesn't seem to affect braking.

I've checked the reservoir and don't see any obvious sign of leaks. I keep the reservoir filled just at Max and try to avoid over filling. I run SRF fluid wt PFC 08s on stock calipers/rotors.


Anyone experience this, or ave any thoughts?

[Polo08816]

Originally Posted by dvas

I've noticed during track days, that I sometimes have a few drops of clear fluid hitting my driver's side windshield, usually just after some hard braking. It seems to be coming from under the hood and, more specifically, from the brake fluid reservoir area, leading to the obvious conclusion that it's brake fluid.

This has occurred on 3 occasions out of 10 or so days this year. It always seems to happen in the first morning session only, going away by session 2 and not occurring again throughout the day. It doesn't seem to affect braking.

I've checked the reservoir and don't see any obvious sign of leaks. I keep the reservoir filled just at Max and try to avoid over filling. I run SRF fluid wt PFC 08s on stock calipers/rotors.

Anyone experience this, or ave any thoughts?

Test the fluid on your windshield on your paint. If it removes your paint, it's probably brake fluid.

[dvas]

Originally Posted by Polo08816

Test the fluid on your windshield on your paint. If it removes your paint, it's probably brake fluid.

Thanks, that's helpful. I might as well close the thread now...

[look585]

Just a guess. Maybe overfilling the res.? or maybe some fluid that has spilled and is being sprayed on the windshield at speed.

Sure you tighten the cap enough.

[dvas]

Yeah, I checked the reservoir. Cap was tight, didn't see any loose hoses, fluid was right at the max level. Not sure if there is a breather valve or something there?

[ZM2]

I’ve always heard not to fill to Max bc the fluid expands under heat. Maybe true? Maybe not?

[rjn]

Are you seeing actual evidence of fluid on the reservoir?

Maybe too simple, but since you mention it only happens in the morning, if the car was outside overnight, seems like it could be water condensation coming from somewhere, and just whipping up on the windshield, until there isn't anymore. I mean, water like that can come from about anywhere.

If it's brake fluid, I've never experienced nor heard of anything like this. Good luck sorting it out

[dvas]

Yeah, I can see that the reservoir area is wet, while every other area is dry. So definitely not just condensation. I'm thinking it's just a function of having topped off the reservoir too high when installing new track pads and essentially a non issue.

[CosmosMpower]

Never had this issue

[Noel911]

I haven't had this issue either. Sorry.

[paradoxical3]

I have never had it splash on my window, but it's very common for BMW's brake fluid reservoir to leak under hard track use. It did it on my X1 and it does it on my M2. Seems to be fluid pushing out from the vent hole.

Since I updated to Essex AP Racing brakes it stopped, presumably due to lower brake fluid temp.

[TimOudin]

Are you sure it's brake fluid? When I took my car out for the first couple of events I got a clear fluid splashing up onto the windshield, leaving some scary streaks. Fortunately, I had 1/2 of the local BMW tech crew around. They were all convinced it was nothing to be concerned about and just a spray on coating BMW covers something under the hood/the underside of the hood with. I forgot the name, but cosmoline sounds familiar. It stopped after a few hot days in which I presume I melted it all off. The diagnosis sort of makes sense as it would only show up when I had gotten the car properly hot.

[dvas]

Originally Posted by TimOudin

Are you sure it's brake fluid? When I took my car out for the first couple of events I got a clear fluid splashing up onto the windshield, leaving some scary streaks. Fortunately, I had 1/2 of the local BMW tech crew around. They were all convinced it was nothing to be concerned about and just a spray on coating BMW covers something under the hood/the underside of the hood with. I forgot the name, but cosmoline sounds familiar. It stopped after a few hot days in which I presume I melted it all off. The diagnosis sort of makes sense as it would only show up when I had gotten the car properly hot.

Not 100% certain, but fairly sure it was brake fluid.

At any rate, Did a bleed last week and made sure not to overfill the reservoir. Did two days at Palmer without any issues and brakes felt fantastic all day with the flush. Problem solved.