Vented brake fluid reservoir?

[V12StealthHunter]

My car has the two little bottles style reservoir with a cap that looks like this;


While cleaning them out one day I noticed that the cap is vented through the center. Is this intentional or has that rubber/plastic seal in the center of the cap just worn out?

I thought brake fluid was hydrophilic as in it likes to absorb moisture from the atmosphere. Or was this not an issue with brake fluid in the 70s?

[azruss]

That's how they are built. That button it pretty tight so it may be just a plug for a cap without a low fluid sender.

[baltobernie]

I don't see any vents; maybe the volume of "make-up" air required is tiny.

I think your cap is missing the membrane button and contacts for low-level warning. Mine looks like yours underneath the orange switch.

[131]

I thought brake fluid was hydrophilic as in it likes to absorb moisture from the atmosphere.

Hygroscopic, so in theory should be replaced annually. The reservoir has to be vented or the fluid level can't fall as the pads wear. Modern vehicles use a flexible seal that can expand into the reservoir as the level falls, but still excludes the outside air.

[V12StealthHunter]

Hygroscopic, so in theory should be replaced annually. The reservoir has to be vented or the fluid level can't fall as the pads wear. Modern vehicles use a flexible seal that can expand into the reservoir as the level falls, but still excludes the outside air.

Ah good to know. Had no idea thats how it is on all cars.

[vandor]

> I think your cap is missing the membrane button and contacts for low-level warning

His Spider never had that, Fiat started that in mid-77.

> Modern vehicles use a flexible seal that can expand into the reservoir as the level falls

You can have that for your Fiat too with these two parts:

http://www.autoricambi.us/product/BR9-0 ... er-Insert/

http://www.autoricambi.us/product/BR9-0 ... rvoir-Cap/

[131]

http://www.autoricambi.us/product/BR9-0 ... er-Insert/

What a top idea, never seen one of those for an early Fiat.