SprintCarDriver

A while back I was discussing how brake fluid had disappered. Figured that it leaked into the booster from the master cyl as there are no visible leaks anywhere. Checked the vacum to the booster and it seems to hold for awhile but not much more than 15 min. after I shut off the engine.

Tonight while I was adjusting the carb, I was going to put the car in gear and as I pushed on the brake pedal, the engine rpm's increased. I seem to remember that was a sure sign of a bad brake booster. Anyone out there concur? Anyother tests that I can do to see if the booster is trash before I order parts and try to take it out of the car

Sure is driving me nuts to have this new/rebuilt 6" rod motor humming and I cant take the car out for a spin...

Thanks

lyonsh

Generally, if your rpm increases when you push the brake pedal, that indicates a possible leak in the booster. My guess is that if you got brake fluid in the booster, it "ate" the diaphragm.

You can test the booster's ability to hold vacuum with a mityvac vacuum pump. Connect to the booster vac line, pump it up, and see if it will hold the vacuum.

woodworkr

From past experience I have found that there are 2 ways of knowing if the booster is going bad. First the obvious is that you will hear air when you press on the brake pedal (that is if the diaphram is totally gone). If there is a slight pin hole or the seal is bad the pedal will get rock hard, and I do mean rock hard, to the point that you almost need 2 feet to get the car to stop. As was said in a previous post, if the seal between the master and booster is bad that will eat up the diaphram. If it were me and I was changing out the booster I would change out the master as well. A classic case of the "while your in there" :crazy:
JoeB

SprintCarDriver

Thanks for the info. Thats what I thought. Replace them both, especially with the history on this machine. If I dont do it now, I will have to within the week. Thanks again...