911 brake fluid breather hose

[Max911]

Good afternoon Gentlemen

I kindly ask your help for the brake fluid breather hose: is it really necessary and where it is originally meant to drop?

My car is a 2,2 T my1970

When I bought the car the brake fluid breather hose went from reservoir to front wing left panel or better between external wing and internal...

Geniously providing a MEGA corrosion...

After my restoration I used the car with the short hose plugged so no breathing
(The car was controlled also by a Classic Porsche dealer and they told me nothing about that)

Then I put ,as Porsche built it, with a long hose trying to get it dropping on the road in a zone far from precious new paint.

Nevertheless I discovered is impossible to find a position where let it drop without spreading before or then some brake fluid on the underside of the car

Disappointed, I removed the hose again and plugged the reservoir. The braking power obviously doesn’t change nor any other feeling on brake pedal or whatever.

On any porsche manual I didn’t find the correct location: so my question for you expert is: shall I let it plugged or is there any potential issues or problem?
Are you able to provide me picture if any of you let it drop anywhere safe and far enough not to spread brake fluid on painted part underside the car?

Thanks again very much
Max

[Lightweight_911]

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I never liked the idea of 'dumping' excess brake fluid to the outside - to be blown onto underside of the car (or the front of a following car) - so in my early 911's I always routed the hose to a small 'catch tank' sited in the smuggler's box ...

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[Max911]

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I never liked the idea of 'dumping' excess brake fluid to the outside - to be blown onto underside of the car (or the front of a following car) - so in my early 911's I always routed the hose to a small 'catch tank' sited in the smuggler's box ...

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Thanks a lot!!

I have the same opinion...

I think that more that in excess is the oil that due to shaking of the car while driving that goes out...
I’m wondering if the plug on reservoir could in certain condition damage the reservoir causing pressure that could cause problems...

[Gary71]

Some brake fluid caps have a tiny breather hole rather than a separate hose. I’m planning to block the pipe and drill a hole if it doesn’t already have one.

[911hillclimber]

^^ Did this to my 73 T when converted to RHD 27 years ago, all good.
I capped-off the original outlet as hard cornering can induce fluid to come out.
Hole in the top is really small, about 1mm.
It only allows for the very small volume changes during use and pad wear. Girling master cylinders have the same vent.

[Max911]

Precious advices as always!

Thanks!

[Mark A]

I'm just thinking about this on my 73T resto. Is there not also moisture exposure in having it open to the elements, strikes me that we all know about brake fluid absorbing moisture but then have a system thats open to the air? Can the system be left plugged or does it need expansion room?

[911hillclimber]

Zillions of cars have this small hole to allow air pressure to equalise as the fluid level drops due to brake surface wear over the years.
Nothing to be concerned about.