Brakes: 10 lb. residual pressure check valve failure

[dday392]

Hello all:
My modified Studebaker has developed a brake problem that I wonder if anyone else has seen. Because my brake peddle started going to the floor after sittng over night, but would pump up and hold steady after a couple of pumps, I suspected a check valve. By process of elimination, I found that the Wilwood 10 lb. residual check valve to the rear drums was not working. When I took the check valve out and inspected it I was shocked! I could see the spring poking through the little "duck billed" rubber check thingy. What could have caused this?
Thanks, Dave

[sweetolbob]

Hello all:
My modified Studebaker has developed a brake problem that I wonder if anyone else has seen. Because my brake peddle started going to the floor after sittng over night, but would pump up and hold steady after a couple of pumps, I suspected a check valve. By process of elimination, I found that the Wilwood 10 lb. residual check valve to the rear drums was not working. When I took the check valve out and inspected it I was shocked! I could see the spring poking through the little "duck billed" rubber check thingy. What could have caused this?
Thanks, Dave

Dave

I won't speculate on why the residual valve failed but Wilwood is a first class outfit that supplies a lot of high performance go-fast brake stuff. I quite sure they would like to know about your issue and help determine why it failed.

I'd get to their tech service ASAP.

Bob

[junior]

further to that, if Wilwood gets back to you with an answer, let us know the reason as those are the valves that are in the Turner brake front disc brake kit, so a lot of us would probably like to know if this is a freak problem, of problematic of the design itself. Thanks, Junior.

[dday392]

Hello again:
I got some tech help on the Wilwood check valve and the failure was my fault, not the valve itself. If the fluid under pressure can not get back to the master cylinder it can deform the rubber check valve because the drum springs are trying to push the fluid back . Two ways are possible. The check valves in the master cylinder were not removed, or the push rod was not adjusted properly. In my case it was the push rod. I had adjusted the push rod two weeks earlier (with my head up my ass appearently). No need for alarm, just don't do what I did.
Dave

P.S. I am replacing both Wilwood valves as the 2 lb. also shows some sign of deformation.

[junior]

Hello again:
I got some tech help on the Wilwood check valve and the failure was my fault, not the valve itself. If the fluid under pressure can not get back to the master cylinder it can deform the rubber check valve because the drum springs are trying to push the fluid back . Two ways are possible. The check valves in the master cylinder were not removed, or the push rod was not adjusted properly. In my case it was the push rod. I had adjusted the push rod two weeks earlier (with my head up my ass appearently). No need for alarm, just don't do what I did.
Dave

P.S. I am replacing both Wilwood valves as the 2 lb. also shows some sign of deformation.

Can you share with us how you incorrectly adjusted the push rod, chances are one of us dumb-asses may do the same... thanks, Junior.

[dday392]

Junior:
It turns out there is more to this than just a bad adjustment. When I found excessive play in the brake push rod I should have questioned "why all the sudden"? In hind sight, I've had dragging brakes for some time and didn't realize it. I've had to give more throttle to leave stop signs and brake dust on my wheels was more than in the past. When I pulled my master cylinder last night I discovered that the piston was not all the way back and, my adjustment of the push rod a few weeks back actually made it impossible for the piston to return all the way back.
Why wasn't the piston returning? Here's what I found. I had 3 washers on the push rod all of them inside the snap ring. One came with the new Jeep dual resivoir and sits inside next to the snap ring, the two others came with the stock push rod from the '53 master cylinder. Those two washers prevent the rod from being pulled out unless you remove the snap ring. I suspected that somehow one of those washers had gotten cocked and held up the piston. I don't remember why I left those two stock washers on the pushrod but now I can see they are not needed, the piston now returns all the way back after removing them.
Two new inline check valves arrive tomorrow and I will keep you posted when I am done.
Dave

[rocket1]

I think the brake fluid is just leaking past the master cylinder piston,usually if you have to pump the brake pedal to get more pedal it indicates a bad master cylinder

[dday392]

Back again and I have properly working brakes. I ended up replacing the front and rear residual valves plus the master cylinder. At first, I put everything back together with just the new residual valves but the brakes took 3 to 4 minutes to release. That's not good in stop and go traffic.
The master cylinder and all the parts inside looked great. No scoring or rust pitts and the cups look fine. I concluded that something must be stuck in one of the passages. Even though I clean the lid of the master cylinder before removing it, it's possible something from the bottom side of the floor could have fallen in the reservoir while manuvering the lid out from under the floor. From now on, I will clean everything in sight and use compressed air as well before flipping the bail.
I still have the bad master cylinder so I will get to the bottom of this.

Thanks for your comments, Dave

[junior]

thanks for the updates Dave. with that big old hemi up front it must be a good feeling knowing you have brakes that work. Junior.