soft brake pedal

57imposter · 2020-03-30 11:02

I have been fighting a soft brake pedal for a couple years. The car stops fine but the pedal is troubling. Since I have lots of free time, these days, I put it up and ran over everything with my vacuum bleeder. The right front caliper seems to be gulping air. Checked the entire system and every joint is bone dry. Next logical step is Google. Turns out a guy had the exact same issue on one of the boards and he got an answer from someone that makes sense. He said he is pulling air past the piston seal. When the brakes are applied, the fluid forces the seal out and prevents a leak but when the piston relaxes, if there is even a small defect it will allow air to pass. I have never experienced anything like this but I have two fresh calipers coming that should be here tomorrow. We'll see.

John Palmer · 2020-04-01 11:02

Yes, it can be frustrating.

I would not over look checking the rubber flex lines. The last time I fought a brake problem it was a hose that the rubber rotted "on the inside" and prevented the brake from fully retracting causing it to drag and it also had the spongy pedal feel. Four new hoses (it was on a swing axle VW) and all was fine again.

The quality of any replacement parts purchased today is questionable. The ethanol added to today's gasoline causes lots of problems in our old collector cars.

57imposter · 2020-04-01 17:49

Thanks, I have braided stainless lines so I'm pretty sure their ok. I have two fresh calipers ready to go on, as soon as I get a descent day. My hoist is outside and I am WAY past crawling around on the floor

mustang6984 · 2020-04-01 21:01

I have a buddy in Richland...he would be happy to crawl around on the floor!

57imposter · 2020-04-02 00:11

Quote from: mustang6984 on 2020-04-01 21:01
I have a buddy in Richland...he would be happy to crawl around on the floor!

Thanks but with the lockdown, there is really no hurry to get them on. He doesn't happen to have a 57 does he? I'm really needing to look at a car with the original bench seat.

mustang6984 · 2020-04-02 01:47

No he doesn't. He is a Festiva re-builder. My 2 '57's were not blessed with them either when I got them. The white one had just been retired from being a 1/4 mile car, and the other was turned into a hot rod. Sorry. When I get back to Port Angeles (I am in Branson right now and will be until this virus dies) I might be able to come up with one. There is an older guy near my shop in Dungeness (outside of Sequim) who has a sedan that still have a bench seat. I haven't seen him for awhile, (he put a bow-tie in the car

for a motor) but the rest is still stock. If you haven't located one by then I will try to catch up with him. I see him now and then at a car show in Port Angeles, and I do know roughly where he lives.
My friend does like cars though, and he does like my Courier. He has an appreciation for the '57's.

57imposter · 2020-04-08 17:26

Two fresh calipers and much bleeding later and I still have a soft pedal. The car stops fine and has a good firm pedal until I start the engine. then it all goes away. I friend has a good power bleeder which I will try as soon as I get the new seat risers finished....As Rosanna Danna said "It's always something."

mustang6984 · 2020-04-08 17:36

Do not feel alone. I have had so many annoying days where I bled until I couldn't stand the sight of a zerk fitting anymore...and still had soft pedals.
I have become a BIG fan of power bleeders...but I have not got one! YET!!! There is one in my future! Let me know how that goes. Bet you send me a string of ha[[y faces! LOL!!!

RICH MUISE · 2020-04-09 11:08

Doug...... The soft pedal is something you've always had, or a development down the road. What disc brake setup/brand do you have, and master cylinder? Vacuum booster or Hydroboost? residual valve on your back brakes? are the backs drum or disc? The bleed valves are at the top of the caliper?

57imposter · 2020-04-10 21:46

Quote from: RICH MUISE on 2020-04-09 11:08
Doug...... The soft pedal is something you've always had, or a development down the road. What disc brake setup/brand do you have, and master cylinder? Vacuum booster or Hydroboost? residual valve on your back brakes? are the backs drum or disc? The bleed valves are at the top of the caliper?

It's a stop-N-Drop front disc. This hasn't always been a problem but I can't remember exactly where it started. It is a new master cylinder and all other components are basically new. Now that I think of it, I had to relocate my proportioning valve when I swapped out my rack for a power box.That may have been around the time this started. Like I said I will try a good power bleed as soon as I get my interior projects done.

Fairlane62 · 2020-04-12 23:08

Sounds like a bad vacuum booster.

57imposter · 2020-04-13 10:33

Quote from: Fairlane62 on 2020-04-12 23:08
Sounds like a bad vacuum booster.

There is a good chance that I don't understand enough about the booster but I don't see how it could cause the problem. Any more info, would be appreciated.

57imposter · 2020-04-13 11:05

Quote from: Fairlane62 on 2020-04-12 23:08
Sounds like a bad vacuum booster.

Went to the ultimate info. source, GOOGLE, and they talked about the booster pin to master cylinder piston clearance. I'm familiar with that spec and it was set properly. I guess it's possible that the lock nut came lose and the gap opened up. Seems kinda far fetched but since I have access to the gauge tool, I'll check it before I go crazy replacing parts.

mustang6984 · 2020-04-13 11:08

How old is your booster? If there is a small vacuum leak, either in the booster or anywhere in your line, you will get the same issue you're suffering from now. Just a thought.
Hugh

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soft brake pedal