Sherwood,

I think you are making a mountain out of a mole hill. The small amount of brake fluid that might vent onto the track is not going to go airborne and land on the paint of the car behind it. It is going to stay on the track and will not cause any problems. We are talking, at most, drops at time.

Coolant does get vented to the ground often which is one reason why they don't allow anything but water or water with something like Red Line Water Wetter in radiators. The quantity is a lot more than you would ever see with brake fluid.

Gasoline gets vented to the ground.

Scott

If gravity acts as you describe, then why is there often a film of engine oil and other fluids on the windscreen and front end of race cars? Oil is more viscous than BF too.

I'm making a point that all fluids should be contained with catch can reservoirs and should be kept within the confines of a race vehicle. It's a safety thing. If NASA, AMA, IRL, MotoGP or F1 allow it, so be it.

... from the NASA pro racing website:
11.4.4
"There should be no fluid leaks from the engine. A radiator overflow of at least one-liter capacity should be used. Oil breathers or vents shall return the oil to the engine or shall terminate in a catch tank of at least one-liter. All hoses carrying fluids should be in good condition with no cracks or other damage."

Sounds like the intent of the regs is to prevent fluids from causing a safety hazard. YMMV.

Sherwood

I unintentionally misled you.

I just checked the routing of the brake fluid reservoir vent line in my race car. It does not actually come out underneath the car as I thought. It is a 3 1/2 foot long tube that is always above the reservoir and terminates in an opening located above and behind the right front wheel well.

So, the tube has enough capacity to handle any overflow that might happen and has gravity working it its favor. If it did overflow, it would most likely make a small mess in the aforementioned opening. The fluid couldn't go anywhere else.

Regardless, I am unaware of any rules that say you cannot have the brake fluid reservoir vent out the bottom of the car on to the ground. If they exist, I would like to see them.

Sherwood: A few drops of brake fluid on the track is a not a safety hazard. That is why the rule books don't specifically call out brake fluid reservoir venting.

Scott

Scott,
Granted, the NASA regs don't address BF spillage. Unsure about other race regs. As I said, BF is corrosive. If you don't mind even a few drops landing on your chassis or suspension or those behind you, up to you. Carry on.

Sherwood

question? I mentioned earlier that a new master cylinder eliminated the leakage problem I had. Can anyone confirm that they have replaced the master cylinder and still have the same issue of fluid going out the vent.

Given that the small reservoirs pre-87 are prone to drawdown/spitting fluid, i'd argue that the amount being expelled by a lot of DE "racers" is pretty substantial. Consider that a lot of these people bleed their brakes quite frequently and therefore top it off quite frequently. Since the factory routing is a straight run of hose & tubing, not a large loop of hose which is indeed a nice catch system (I have this on my fuel cell vent hose), I think a good portion of that fluid is a straight dump on the ground.

I don't have a direct comparison of master cylinder replacement. But I think your observation is a good one. My comparision is my 87 car which has gone thru various stages of brake fiddling. One change was a brand new 930 master cylinder. That reservoir was admittedly vented as factory but I never had any problems with the reservoir level dropping at all, even when freshly topped off. The 79 car started out with the small reservoir on it and its level dropped just like everybody else's- vented to a catch bottle. I just left the level at 1/2 full based on others' similar experiences

I recently switched to the later G50 reservoir and it didn't fix the problem. I left the catch bottle on there because I think it's good practice to have that means of collection- for track protection or bonehead protection (when I forget to clamp off the vent hose during bleeding). The catch bottle had a bit of fluid in it after my last race event. Less than with the older reservoir. So I think you're onto something with the master cylinder since my '79 master is an old 930 unit.

SC Overflow Defeated
 

OK - I am now convinced that the cause of fluid loss from the reservoirs of SCs (and 3.2s, if they are set up the same) is due to the position of the breather/overflow of the reservoir. Since it points out the left side, on hard right hand corners on a race track, fluid is going to be expelled from the reservoir. This seems to be the nearly universal experience, and guys with these cars are constantly checking, and from time to time refilling, their reservoirs.

I made this modificaton, so the breather exits the top.

http://forums.pelicanparts.com/uploa...1348121115.jpg

Wife and I ran hard for two days this past weekend with this setup. Spilled nary a drop. I should fabricate a more elegant holder for my low buck (no buck?) catch can.

Since the pre-power brake 911s didn't have this problem, I attribute that to the fact that their reservoirs (one shown in picture) vented to the rear. Mighty as our engines are, we don't develope the Gs going forward that we can braking or cornering.

On a different note, not having any Hawk Blue pads with enough material left, I decided to run a new set of Mintex street pads. Bad decision - fronts were worn to metal before end of weekend (one pad, others almost), and rears were down to a mm or so. I wonder if Textars or Jurids would wear equally as fast?

But no fluid issues.

All I know is new mc leak went away

I think it is simply a case of the fluid making it into and out of the reservoir vent from sloshing around. There's no pathway for the fluid to return. 2 suggestions:

Run a lower fluid level and investigate making a better baffle.

Change reservoirs.

For example, a motorcycle reservoir has a rubber accordian between the fluid and the lid. When fluid is displaced, the accordian moves, but it always acts as a barrier to prevent the fluid from reaching the vent hole. I would imagine there is a reservoir available from one of the brake manufacturers (Brembo, AP, etc) that might work better in competition. Using two reservoirs is also a possiblity.

JR

Guys, the solution is very easy. Create a small vent hole in the cap and clamp off the overflow tube (or remove it and cap the nipple). See post 39. Cover the cap with a pretty rag if you want, but I have never lost fluid out of the cap. There is no more moisture exposure this way than with the stock arrangement.

In my case the air rushing through the open brake duct hole of my new FG bumper and past the end of the overflow tube directly behind the hole created a venturi effect that sucked the fluid out of the MC much faster than the usual sloshing and dripping. In one 20 minute session at Mosport I lost 50% of the fluid. The mess under my car downwind of the vent tube was massive. I made my modification in the paddock, and it has been 100 % fine ever since, so I've never felt the need for anything more fancy or complicated.

I have a follow up question to this excellent thread. I want to know the exact routing of the brake fluid overflow tube. This is for a 1981 SC. I know it goes out the right of the reservoir, around the back of it via a clamp, then routes to the fender or tub on the right side of the compartment, then down into the wheel well, then to the front of the car.

But, I have not been able to locate the hole in the body that it goes through. The reason I care is because my hose is probably the original and I have cracked it (due to pinching it) with the crack being between the reservoir and body. I'd like to replace this hose but I can't see exactly where it goes through the body.

This is on a race car and there are many extra thick wires there for the electric cut off switch which is mounted back there behind the brake fluid reservoir. Is the through-body spot supposed to be easy to see and reach?

I found the answer in this thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/605293-help-brake-fluid-overflow-line.html

Bumping this old thread as I've been having the same issue, brake fluid escaping from the vent on hard right turns. After a spirited drive I'll notice a wet spot on the ground in front of the left front tire, just below the brake fluid vent exit.

My vent was 'incorrectly' routed from the res, directly left to the inner fender, then forward and out. I noticed on the PET that there is a metal clip that should secure the vent line in a flat 'U turn' behind the res. Not having the clip (and neither does Pelican) I used a solder iron to melt two holes in the res upper lip and zip tied the vent into a flat 'U turn'.

Will report back in a week or so if there is an improvement. Also, notice the height of my brake fluid in the picture, it is about 3/4" down from the top. It was full a few weeks back...

Also, notice the ruined paint, my original vent line was dry rotted and leaking fluid :mad:

http://forums.pelicanparts.com/uploa...1580260178.jpg

http://forums.pelicanparts.com/uploa...1580260178.jpg

Simply run the overflow line into a (1/2 pint) plastic bottle and secure it up front somewhere. That's what we did in all my 911 race cars, never an issue.

A follow up on my modification which was a microscopic drill bit to the top of the cap and blocking off the drain plug...

No noticable loss of fluid and no noticable fluid in the over flow containment area. It's been like that for 8 years or so with plenty of spirited driving.

I'm going to call the 'U-Turn' brake fluid vent a success. After 200 miles of my favorite twisty roads my brake fluid is no longer escaping out the vent.

Clearly the dedicated overflow bottle is superior for track work, but good to know that the correct routing (as engineered by Porsche) works just fine for spirited driving, straight shot to the fender, does not.

The vented cap like Kemo posted is probably fine as well, but would make a heck of a mess if you ever truly boiled your brake fluid...

http://forums.pelicanparts.com/uploa...1580860905.jpg

?? What king of pressure is that hose releasing to be able to lift the tires off the track? ??
Have you tried pointing it towards the rear to generate some propulsion/acceleration ??

:D:D:D:D

Turning in autocross. Hose is just hangin' there.

Full picture:
http://forums.pelicanparts.com/uploa...1580927521.jpg

For those who adhere to the factory outflow path of the overflow tube, keep track of the chassis sheet metal adjacent to that exit point. BF does an excellent job at removing paint which then exposes the underlying sheet metal to the elements.

S

I had this issue with my 85 911 running DE. at first very worried about where the BF was going.

once I realized it was out the overflow, connected a little bottle to the overflow line. and based on a suggestion made a couple loops in the line. those loops seemed to help reduce the amount. maybe by not providing any suction of the fluid going out and down an open tube.

sold that car.