53 Roadmaster Kelsey Hayes master-booster unit

I'm restoring a 53 Buick 76 series with power brakes and have just solved a problem with the rebuilt power brake unit. 4-5 years ago I sent the brake unit to Karp Brake rebuilders in CA for a complete rebuild.Toward the end of last year I bled the brake unit at the wheels and master and had a good hard pedal til I started the engine. After a bit of engine operation the brake pedal sank to the floor and the brake fluid in the remote reservoir disappeared. I tried adding more brake fluid but it too disappeared.

I failed to find any hydraulic leaks in the lines or master so I removed the vacuum line at the master and found the 1 way valve was wet. Talked with Karp and he stated he felt the cylinder seals were leaking and asked me to return the unit. When I had the unit off the car I found brake fluid in the vacuum chamber which confirmed his and my suspicion.

In a phone call yesterday with Jeff at Karp he stated he stopped using a rubber parts supplier (parts) because their rubber formulation did not work out well. He is replacing the leaky seals with parts from another vendor and feels these new seals will do the job.

This setback was a disappointment but I hope we are headed toward a permanent Fix.

Chrysler products used the same unit but located it on the firewall which makes for much easier removal. I've had experience with several Chryslers with this unit with no problems with seals or operation.

Here is hoping noone else has the same luck.

Marty Lum

Thanks for sharing that Marty. May be something good for us 54 owners to know also.

Thanks Marty. I was told to junk my KH cylinder and get a 55 for our 53 model 76 but it is working well. I think it must have had the recall update or a 1990 rebuild with improved parts. The cups looked good. You did not say which fluid you use. I am interested to know? I use the silicone dot 5.There is a modern unit which some hot rodders use which mounts similarly and provides separated front and rear lines. I think I could make that work....but mine seems to be working. Do the judges look above the belly pan?

And thanks for your prior help. I have the back windows working now.

Pat

I'm restoring a 53 Buick 76 series with power brakes and have just solved a problem with the rebuilt power brake unit. 4-5 years ago I sent the brake unit to Karp Brake rebuilders in CA for a complete rebuild.Toward the end of last year I bled the brake unit at the wheels and master and had a good hard pedal til I started the engine. After a bit of engine operation the brake pedal sank to the floor and the brake fluid in the remote reservoir disappeared. I tried adding more brake fluid but it too disappeared.

I failed to find any hydraulic leaks in the lines or master so I removed the vacuum line at the master and found the 1 way valve was wet. Talked with Karp and he stated he felt the cylinder seals were leaking and asked me to return the unit. When I had the unit off the car I found brake fluid in the vacuum chamber which confirmed his and my suspicion.

In a phone call yesterday with Jeff at Karp he stated he stopped using a rubber parts supplier (parts) because their rubber formulation did not work out well. He is replacing the leaky seals with parts from another vendor and feels these new seals will do the job.

This setback was a disappointment but I hope we are headed toward a permanent Fix.

Chrysler products used the same unit but located it on the firewall which makes for much easier removal. I've had experience with several Chryslers with this unit with no problems with seals or operation.

Here is hoping noone else has the same luck.

Marty Lum