Here's one that is stumping my father, he has a 1951 Ford that came with drum brakes but has been converted to disc brakes all around. The brakes are dragging and no one can figure out why. The master has been replaced along with the booster and proportioning valve. I suggested that maybe someone used DOT3 instead of DOT5 not thinking about the conversion, causing the rubber lines to get gummed up. All four wheels are dragging, not just one or two. The proportioning valve was replaced with the correct valve for 4 wheel discs. They removed a vacuum line but no significant change was noticed. The car has been at the shop for about a week and they can't figure it out either. My suggestions are- 1- check the lines for signs of using the wrong fluid. 2-put a return spring on the pedal itself and see if that does anything. 3-ummm, I guess I only have 2 suggestions. Is there anything that we are overlooking? Thanks for any suggestions, Ron
DOT 5 fluid is generally only recommended or racing cars but in any case it is compatible with all brake components. Brakes that don't release are usually cause by one of two things. 1. Bad hoses that have internally failed or 2. The push rod from the brake pedal to the master is too long. Even the slightest pressure will not allow the brakes to release fully. #2 is really the most likely cause as a result of a conversion. The rod needs to be adjusted a bit shorter to ensure no pressure is applied to the master cylinder while also allowing a full stroke when applying the brakes.
X3 A 1/2 turn too far into the master cylinder will cause that exact problem. The key to proper push rod length is "0" preasure on the MC piston and "0" slop(free play)
Sounds right to me...or a colapsed rubber hose. But doubt all could be colapsing at same time. Most likely those hoses are new or were when conversion was done.
All good suggestions. I think you hit the nail on the head with the pushrod length. I will let you know as soon as someone figures it out. I thought all new vehicles use DOT5? My motorcycles use 5. I know that if you mix 5 with 3 it will cause the inside of the hose and any other rubber pieces to disintegrate. The car is at the brake shop and they are only working on it sporadically, I am hoping they have it figured out by the end of next week. Again, thanks for the replies. Ron
Dot-5 Too expensive for mass production but I like it just for the "0" moisture factor when I do or re-do ah "keeper". Do it rite once and you'll be toes up before it needs to be done again
I vote for #2 also. If all 4 are dragging it is the only common link between the two reservoirs. Crack the bleeder valves and relieve the pressure. If the brakes free up then the pushrod is most likely your culprit. If not there is a chance the pads are too thick or rotors are too thick.
They figured it out. Evidently there is some kind of adjustment in the booster or between the booster and master, not the pushrod but some other kind. I didn't get the details, but the brake system is some kind of kit that you can buy, the discs are pretty small. I was thinking it was a system off of a more modern car. The car was at a pro brake shop, you would think that they would have some kind of an idea about there being some kind of adjuster. Maybe it was a kit they had no experience with. Anywhoo, I appreciate the replies. Thanks, Ron
-There is also a short rod between the booster and the master. Probably too long. Also the master sould be for disc brakes. Tell dad to get out and cruise tonight!
