brake fluid loss at track-overflow??

gchappel · 11-19-2001, 09:15 AM

My 85 carrera just came back from 2 great days at Sebring- thanks PCA!!
Throughout the event I lost about 1/4 of the reservoir of brakefluid. I had a few drips on the ground underneath the front drivers area- right where the overflow tube is, but didn't think that was it. Everything else checks out- calipers dry, no fluid around MC, good brakes throughout. When I was tech-ing my car after the event, it is clear that a good deal of brake fluid came out the overflow tube, and coated the underside of the car.
Now I know I am a "GREAT" driver, and can pull many more G's than my car was designed for- yeah right. We were pushing it pretty good, this old car holds its own (especially for an everyday driver) in the instructor group, but nothing more than every other car out there. Is it normal to drain this much brakefluid out the overflow- maybe that is what it is for, but I don't see others with the problem. I fill the reservoir basically up to the top- to the top seam--am I overfilling it?? Is there sometype of valve or anything in the overflow system? Should I just clamp it off when I am at the track? Can I reroute the overflow tube someway, maybe looping it above the reservoir ?
Thanks for any help here- want to go fast, but more want to stay safe.
Gary

orbmedia · 11-19-2001, 09:38 AM

The fluid bowl was just a little too full, it's common. Just keep your eye on the level to make sure you're not losing fluid from the other seals in the calipers. You would notice streaks on the wheels. A tiny bit of seepage is not a problem when on the track.

gchappel · 11-19-2001, 10:56 AM

Thanks, that is what I thought but just wanted to confirm it
Have a good holiday
Gary

masraum · 11-19-2001, 11:59 AM

Just curious, being that you were at the track could the heat generated have caused the fluid to expand like our oil causing the overflow? That would explain why the level was low after the car cooled. Just thinking outloud.

lonewolf · lonewolf's Garage

he,s right
thats what happened to you . your brakes got so hot that the fluid as expanded or even boiled slightly . next time don,t have it as full, make sure you wash of the brake fluid .

Superman · 11-19-2001, 04:34 PM

Do not plug the overflow hose. I'd start with just a little less BF. And yes, it probably is caused by the violent forces dictated by your gifted and aggressive driving maneuvers, compared to the other drivers. At least that would be my explanation if I were you.

rfix'n · 11-19-2001, 04:40 PM

This leads to the question of how full the bowl should be? There is no fill line on mine.

gchappel · 11-20-2001, 04:30 AM

Can "boiled " fluid or heat from the calipers really make it back into the reservoir and increase the volume in the reservoir? I didn't think that hot or even boiled fluid in the caliper could effect the fluid or level in the reservoir on the other side of the MC.

rstoll · 11-20-2001, 04:44 AM

Quote:

Originally posted by gchappel
Can "boiled " fluid or heat from the calipers really make it back into the reservoir and increase the volume in the reservoir? I didn't think that hot or even boiled fluid in the caliper could effect the fluid or level in the reservoir on the other side of the MC.

Why not? The fluid level goes down in resevoir as pads wear, and comes back up when you renew pads.

orbmedia · 11-20-2001, 09:15 AM

I don't think brake fluid expands much when it gets hot. If the fluid actually boiled the pedal would have gone to the floor.