Brake pedal goes to the floor when I start the engine
03-02-2018, 05:49 PM
#1
Teching In
Thread Starter
Join Date: Sep 2009
Posts: 28
Likes: 0
Received 0 Likes
on
0 Posts
Brake pedal goes to the floor when I start the engine Howdy, been a while since I posted. Just recently when I start the car my brake pedal goes to the floor. It does not go the floor when not running. I have an ls1 in a 61 Impala. Any thoughts?
03-02-2018, 07:12 PM
#2
TECH Resident
Probably a small leak in the system. Check the fluid level then start the car and pump the brakes a bunch and check the level again. If it's lower you look for the puddle. If the fluid level stays the same then it's time to swap out the booster.
03-02-2018, 07:18 PM
#3
Teching In
Thread Starter
Join Date: Sep 2009
Posts: 28
Likes: 0
Received 0 Likes
on
0 Posts
So far there are no leaks. I have disk brakes all around and a 7" booster. Been fine for years, but now when I start the car the pedal goes to the floor. The pedal is strong (normal) when engine is not running. What's interesting is after driving for a little while the pedal gets better. I have no clue. What can go wrong with the booster, the diaphragm?
03-02-2018, 07:22 PM
#4
TECH Fanatic
Yes, I'm thinking brake booster. Remove the vacuum line to it and cap it off so there's no vacuum leak to the engine. Check brake pedal. My guess is that your brake pedal will be fine . . . . replace brake booster.
Rick
P.S. - I had a bad "hiss" during the vacuum leak once on an S-10 truck. Do you hear a hiss?
Rick
P.S. - I had a bad "hiss" during the vacuum leak once on an S-10 truck. Do you hear a hiss?
03-02-2018, 10:58 PM
#6
Wouldn't a brake booster or vacuum issue mean the pedal would NOT go to the floor because you'd have reduced or no power brakes?
I'm thinking leak, or air in the system. Bleed the brakes and make sure you get a solid stream out of each corner of the car.
I'm thinking leak, or air in the system. Bleed the brakes and make sure you get a solid stream out of each corner of the car.
Trending Topics
03-03-2018, 12:57 AM
#8
TECH Fanatic
03-03-2018, 11:50 AM
#10
Teching In
Thread Starter
Join Date: Sep 2009
Posts: 28
Likes: 0
Received 0 Likes
on
0 Posts
Ok good stuff. I had a master go bad about 4 years ago. I am running a Kugel 90o system under the dash. When first installed everything was normal. When the master went bad 4 years ago it was a master, so I guess we R&R the master and see if that fixes it. Thanks guys!
03-03-2018, 02:18 PM
#11
Teching In
Thread Starter
Join Date: Sep 2009
Posts: 28
Likes: 0
Received 0 Likes
on
0 Posts
Before I decide what to do I have another question. Why is the pedal ok when the engine is not running and the only thing that changes when I start the car is the power assist? In other words if the pedal is good without assist, why is it not good with the power assist? Does that indicate it is the power assist?
03-03-2018, 03:29 PM
#12
If you can pump the pedal with the engine off and get pressure, but it goes spongy or the pedal goes to the floor with the engine running, you have air in the system.
The booster decreases pedal effort, so you're applying more pressure to the hydraulics with the same amount of force to the pedal. Air compresses, brake fluid doesn't.
The booster decreases pedal effort, so you're applying more pressure to the hydraulics with the same amount of force to the pedal. Air compresses, brake fluid doesn't.