With engine running brake pedal goes to floor, very minimal stopping power.

MARKBOYCE

MEMBER
1994 CHEVROLET VAN
98,000 MILES

With engine running brake pedal goes to floor, very minimal stopping power. Calipers and wheel cyls replaced recently. Front and rear brakes still have decent amount of material left on pads, rotors, shoes and drums. Front rubber caliper hoses are dry, rear rubber ”T” block hose is dry. Havent started troubleshooting m/c or booster yet but guessing problem might be in one of those. Well I changed out rear brake hardware, bleed brakes and same thing brake pedal went to floor. I noticed when wife was pumping brakes (engine on) that mc was bubbling up in resivor. But when engine is off have very strong brake pedel. So confused on where my issue is booster or mc
Thank you

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

It does sounds like an issue with the master cylinder. If the seals inside the master cylinder is bad it will not hold pressure and the pedal will go to the floor.

Here is a helpful guide:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Keep in mind that if you have dry rotted hoses, they need to be replaced as well as when the hose gets worn it can break and you will not have any brake pressure.

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.

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