Brakes Brake fluid disappearing?

opihinalu · May 13, 2022

I gutted my proportioning valve and I replaced it with an adjustable one and it worked well for a few test drives (no leaks) and then I let my car sit for a couple months while I worked on it more. I glanced over at my brake fluid and it was obviously lower than it was before. Today I looked again and it’s almost empty. I haven’t driven the car. I checked all of my work and it isn’t leaking from anywhere. Is it possible for brake fluid to leak without and driving or any compression of the brakes? Anyone have any ideas?

limp · May 13, 2022

When you can't find a leak anywhere, its usually the Master Cylinder leaking into the booster which is then being burned in your engine, which is why there is NO evidence of leaking

Mustang5L5 · May 13, 2022

Yup. It's leaking somewhere.

Brake fluid doesn't really evaporate. If anything it absorbs moisture so your level should actually rise if you left the system open.

Like limp said, back of the MC into the booster is a common spot if you don't see any leaks out on the wheels or lines

General karthief · May 13, 2022

Two places to look for fluid leaking into the booster
Under the master cylinder traveling down the booster or more likely (since you see no evidence of a leak) into the cabin beneath the carpet, pull the carpet back from under the brake peddle.

opihinalu · May 13, 2022

General karthief said:
Two places to look for fluid leaking into the booster
Under the master cylinder traveling down the booster or more likely (since you see no evidence of a leak) into the cabin beneath the carpet, pull the carpet back from under the brake peddle.

Mustang5L5 said:
Yup. It's leaking somewhere.

Brake fluid doesn't really evaporate. If anything it absorbs moisture so your level should actually rise if you left the system open.

Like limp said, back of the MC into the booster is a common spot if you don't see any leaks out on the wheels or lines

limp said:
When you can't find a leak anywhere, its usually the Master Cylinder leaking into the booster which is then being burned in your engine, which is why there is NO evidence of leaking

Thank you guys for the super helpful info. Well check this out tomorrow.

Brakes Brake fluid disappearing?

opihinalu

Active Member

limp

wrap a little cheese around it and its a done

Mustang5L5

That is…until I whipped out my Bissell

General karthief

wonder how much it would cost to ship you a pair

opihinalu

Active Member

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Brakes Brake fluid disappearing?

opihinalu

Active Member

limp

wrap a little cheese around it and its a done

Mustang5L5

That is…until I whipped out my Bissell

General karthief

wonder how much it would cost to ship you a pair

opihinalu

Active Member

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