OK, I have 4 wheel drum brakes, new 1" master cylinder dual 7" booster. When I first apply my brakes I can stand the car on its nose but then I lose my braking power right away.. The pedal is soft and I have to stand on the pedal in order to get it to stop. What can be my problem?
Sounds like the booster isn't getting enough vacuum to replenish it's needs...sometimes if you have a low vacuum problem you need a canister to hold reserve vacuum...double check to see that your check valve is working...sometimes it allows a back-feed and the booster can't maintain. There is a vacuum spec for most boosters that tells you how much you need coming from the engine to keep the booster working. And a final note...the booster, even though it's new can be defective. Sent from my iPad using Tapatalk
What I mean by that is that I can pull the car out of the garage and hit the brake and have great brakes, but drive 100 yards down the road and I have to stand on the pedal as it is almost to the floor to get it to stop.
I have a reserve canister and I have also tried an electric pump which made no difference. I replaced the master cylinder and booster because I had this problem with the old one and just figured to eliminate the old one as being the problem which obviously wasn't the problem.
Depending on the master you bought the residual valves should already be installed in the ports on the master? Do you have other valves as well? Sent from my iPad using Tapatalk
Old rubber hoses plugging on the inside? Heat to close to brake parts? Vacuum port dedicated to brakes only? Throwing darts at a wall till pic's show up!
Is this a ebay master set or reputable company. If reputable get a warranty xchange. Or like.post above bad hoses collapsing Or both bad master and hoses.
If by chance you got a master for disc brakes and then had one residual valve in backwards that could also account for your issues. Did you replace all the brakes hoses? Sent from my iPad using Tapatalk
Master cylinder from Summit Racing for Drum/Drum, Drum/Disk application. Like I said prior this also was my problem before buying a new one.
I have plenty of fluid when I bleed the brakes so I'm fairly sure no hoses are collapsed. It is confusing that the brakes are great every time I first apply them then lose them.
Did you bench bled the master before install? The master can trap a bubble of air and still bled the system o.k. Sent from my iPad using Tapatalk
Are all the internal mechanisms in the drums installed properly? Are the primary (small) shoes towards the front? Sent from my SM-G965U using The H.A.M.B. mobile app
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