desoto1939 Posted May 20, 2018 Report Posted May 20, 2018 Now that the warmer weather has arrived here in Valley Forge Pa. I have had some time to work on my brakes on my 39 Desoto. i puller the drum and found nothing leaking at the wheel cylinders. I did havea good pedal and then one day the pedal went to the floor. i was able to get pressure and a good pedal but a couple of days later it went soft again. Well i pull the front carpet out of the car, took out the two metal floor boards. Disconected the brake pedal linkage and removed the mastercylinder that is bolted to the frame. Did a rebuild. Took it all apart and there was no issues with the rubber seals and or any scares inside the MC. rebuilt it and then bench bleed the MC. It is now back inthe car with a good hard pedal all I need to do is road test. The other day I was looking at all of the internal parts and when i looked very carefully at the relief valved I then noticed a very small pin hole or tear in the rubber seal. After the air had dried the valve the hole was more visable. So the smallest compontnet is what failed after driving the car for 30 years. i rebuild the MC 30 years prior with Dot 5 fluid. i guess not too bad after 30+ years. Always look for the none obvious item. Rich HArtung desoto1939@aol.com, 2 Quote
Adam H P15 D30 Posted May 21, 2018 Report Posted May 21, 2018 Rich, just curious, was it the residual pressure valve? Rubber flap thingy that goes in just before the back bolt? I’m probably not being clear, lol. Adam Quote
desoto1939 Posted May 22, 2018 Author Report Posted May 22, 2018 22 hours ago, Adam H P15 D30 said: Rich, just curious, was it the residual pressure valve? Rubber flap thingy that goes in just before the back bolt? I’m probably not being clear, lol. Adam Adam The check value or residual valve sits inthe very front of the MC. It it near the hole that goes to the brake line. It is a push on to the spring then the rubber cup then the thin brass washer then the piston. The valuse control the flow of the brake fluid. this is on my 39 Desoto so each MC might be a little different. rich Hartung Quote
Adam H P15 D30 Posted May 22, 2018 Report Posted May 22, 2018 Sorry for the confusion, I think your master cylinder faces opposite of mine (forward) in your 39... Quote
desoto1939 Posted May 23, 2018 Author Report Posted May 23, 2018 10 hours ago, Adam H P15 D30 said: Sorry for the confusion, I think your master cylinder faces opposite of mine (forward) in your 39... yes you are correct. RichHartung Quote
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