Pedal height after changing power booster
Thread Starter
Intermediate
Joined: Dec 2006
Posts: 46
Likes: 0
From: Bountiful Utah
Pedal height after changing power booster
I did the deed and changed the power booster in my '87 coupe. Helps to have little fingers. After installing though (and before reattaching the master cylinder...I pushed the brake pedal by accident and the pedal went down about 6 inches and wouldn't come back no matter how hard I pulled. This screwed up the brake light switch position, of course and now that I have put everything back together the pedal is near the floor before anything happens at all and the brake lights stay on. The adjustment thingy for the lights doesn't have anywhere near the adjustment to compensate. Anyone deal with this before? Thanks!
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Sounds like the actuator rod is way out of adjustment. This rod comes out of the booster and pushes the master piston. It should be about 1/8 inch from the piston when the pedal is up. New boosters usually need this adjustment however your travel is really excessive. Compare the rod length to the original. This would be for normal operation.
Now, make sure the part is correct and if it might be defective. Compare the two boosters to see if there is a difference in something.
Now, make sure the part is correct and if it might be defective. Compare the two boosters to see if there is a difference in something.
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
Sounds like the actuator rod is way out of adjustment. This rod comes out of the booster and pushes the master piston. It should be about 1/8 inch from the piston when the pedal is up. New boosters usually need this adjustment however your travel is really excessive. Compare the rod length to the original. This would be for normal operation.
Now, make sure the part is correct and if it might be defective. Compare the two boosters to see if there is a difference in something.
Now, make sure the part is correct and if it might be defective. Compare the two boosters to see if there is a difference in something.
If there is no relief for the fluid pressure with the brakes not applied, heat buildup under the hood can cause the brakes to gradually apply themselves (even though your foot isn't on the brake pedal) and cause brake drag that can ruin your day.
Tom Piper
Thread Starter
Intermediate
Joined: Dec 2006
Posts: 46
Likes: 0
From: Bountiful Utah
Yes, I replaced the m/c as well. In looking under again last night, the pedal is about 1.5 inches away from the brake light adjustment screw. I bench bled the m/c and realize that it will help to bleed all the brakes, but the question is about the excessive play right off the bat.
I'll give an update after bleeding the brakes this afternoon. I hope I am just worrying about nothing ....except for the gap that will have to be made up someway. I can't see how to adjust the screw either, too tight to turn it while the wiring is hooked up under there. Suggestins? Thanks!!
I'll give an update after bleeding the brakes this afternoon. I hope I am just worrying about nothing ....except for the gap that will have to be made up someway. I can't see how to adjust the screw either, too tight to turn it while the wiring is hooked up under there. Suggestins? Thanks!!
Thread Starter
Intermediate
Joined: Dec 2006
Posts: 46
Likes: 0
From: Bountiful Utah
Bled the brakes front and rear as well as the m/c. Pedal still has the same free play as before. The pedal stops (going back) 1 and 1/2 inch from the brake light adjuster and about 6-7 inches freeplay (going down) before it feels good. And yes, I did a very thorough bleeding. All this happened when I changed the power booster. If I can't figure it out, I guess I will have to change the booster out again. I got it at NAPA by the way. Any suggestions would be great. Thanks!
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Sounds like a defective booster. The master cylinder can't prevent the pedal from coming back up, and I don't think it's possible for the booster pushrod to be short enough to give 6" of slop in the pedal. Remember, most of these "remanufactured" parts are assembled overseas by people with no education.
Racer
Joined: Sep 2004
Posts: 258
Likes: 0
From: Coram NY
CentralCoaster is right, I just went through the almost the same thing (pedal wouldnt come back up all the way)and it was a bad rebuilt Power booster, I tested my 2nd unit before I even installed it. what you do is connect the vacuum line (outside) and start up the car, you should be able to push the booster in with your finger and when you release it, it should go back to neutral (exactly the same place as it started from).
I gambled the the 2nd one would be good and it was, a mechanic friend of mine told me he has received 2 in row that were bad.
- Tom
I gambled the the 2nd one would be good and it was, a mechanic friend of mine told me he has received 2 in row that were bad.
- Tom
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