| [GMCnet] Sensitized Boosters Leaking problem solved [message #235283] |
Mon, 06 January 2014 15:51  |
Emery Stora
Messages: 959
Registered: January 2011
Karma:
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Senior Member |
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There have been a lot of posts on this topic recently.
I had put in a sensitized booster many years ago that I got from Bob Lamey when he was in business in California.
I had no problem with it and it did not leak.
I later installed a P-30 master cylinder and found that I had a slow vacuum leak at the booster. Later I put in a 34mm master cylinder and still had the small leak.
The bracket for the master cylinder was put between the booster and the master cylinder instead of at the front of the master cylinder since the bracket would not fit over the front of the master cylinder. I hen used a longer push rod. Leigh Harrison does sell a bracket that will fit over the 34mm master cylinder but I did not purchase one.
When I would apply the brake pedal it would slowly sink down. My vacuum pump would also start up as soon as I applied the brakes. I didn't think too much about it until I started hearing people talk about leaking boosters.
Dave Lenzi discussed the problem at one GMCMI convention and said the rubber seal between the booster and the master cylinder which the push rod goes through often leaks when people replace the booster or the original master cylinder. I got a new seal and it helped some but still did not totally stop the leak. At the Branson GMCMI convention Dave Lenzi indicated to me that he was now machining a plastic part that would go over the "nose" of the master cylinder and press against the rubber seal. I got one from him and installed it. It worked just as Dave said it would. It provided a good seal between the rubber seal and the rear of the master cylinder.
My problem was SOLVED! No more leaking.
Dave had explained that the problem occurred when boosters or master cylinders were replaced because of the differences in the dimensions of boosters and master cylinders. He pointed out that several people have also now used metric master boosters and that the hole is about 1/2" greater than the master cylinder "nose" diameter so that when the master cylinder is bolted in place it often gets "cocked" or mis-centered and doesn't seal properly. Other times the "nose" is too short to seal properly against the booster seal. Dave says that when he provides his machined plastic part he has to know the diameter of the hole in the booster and also the outside diameter of the master cylinder "nose" that fist into the booster. There are also cases where people have lost the rubber seal when they replace their master cylinder.
Dave is planning on putting on a seminar about boosters and master cylinders at the Montgomery Texas convention. It should be a good one and I am sure it will be very enlightening one.
I think we can now tell Bob de Kruyff that all sensitized boosters DON'T leak but very ofter the connection of the rubber seal with the master cylinder does leak do to a mismatch between the dimensions of the replacement booster and/or the master cylinder.
Emery Stora
77 Kingsley
Frederick, CO
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