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Joined: Dec 2007
Posts: 50 Likes: 1
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Dec 2007
Posts: 50 Likes: 1 |
Hello everyone,
I am restoring my father's 47 Chevy Convertible. We are 95% complete. The current problem is that all four brakes won't release after we adjust the brakes. The master cylinder has been rebuilt along with all brake cylinders along with new brake lines. We adjust the brakes and they seem fine until we drive it a few blocks and the brake pedal becomes very stiff with no travel and the brakes on all four wheels are very tight. We have gone through adjusting the brakes a couple of times and each time the brakes get tight and the pedal is stiff with no travel.
Any thoughts on what is causing the problem and/or what to do to fix the issues? It is like the hydraulic pressure won't release.
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Joined: Jan 2008
Posts: 819 Likes: 6
ChatMaster - 750
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ChatMaster - 750
Joined: Jan 2008
Posts: 819 Likes: 6 |
Sounds like the piston in the master cylinder is not coming back far enough to let the fluid return. An easy check is when they get tight crack open a bleeder on a wheel cylinder, if that releases the brakes then check the adjustment on the rod going into the master cylinder.
Dens Chevys 1927 Speedster 1928 coupe 1941street rod 1947Fleetline 4 door 1949 1/2 ton Pickup (sold) 1954 210 4 door 1972 Monte Carlo 2003 Corvette convt..
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Joined: Dec 2007
Posts: 3,674 Likes: 55
ChatMaster - 3,000
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ChatMaster - 3,000
Joined: Dec 2007
Posts: 3,674 Likes: 55 |
Dens41 is going good advice. It sounds like the piston is not coming back far enough to uncover the return port to the reservoir.
There should be a small amount of free play before the brake pedal starts to push on the piston in the master cylinder. Look in the shop manual for how to adjust toe board clearance.
Rusty
VCCA #44680
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Joined: Jan 2002
Posts: 30,412 Likes: 116
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,412 Likes: 116 |
instructions are in the shop manual.
Gene Schneider
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Joined: Sep 2009
Posts: 6,673 Likes: 18
ChatMaster - 6,000
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ChatMaster - 6,000
Joined: Sep 2009
Posts: 6,673 Likes: 18 |
I agree with all the advice above. Another consideration to consider is that when adjusting the wheel cylinder it is generally best to lock the wheel from turning using arm pressure on the casing then back off 4 or 5 clicks until the wheel will turn but a little shoe to drum facing is heard. If the suggested help of adjusting the travel of the MC innards doesn't help you may consider your wheel cylinder adjustment. As Gene pointed out, all this is in the manual which is full of good stuff and well worth the price..  Good luck. Charlie 
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Joined: Jul 2005
Posts: 3,180 Likes: 8
ChatMaster - 3,000
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ChatMaster - 3,000
Joined: Jul 2005
Posts: 3,180 Likes: 8 |
As your master cylinder has been rebuilt, was it sleeved? I had a 1939 master cylinder sleeved, but the second hole was not drilled into the sleeve for the compensation port, the compensation port is only a very small hole, and inserting a checking wire is needed to ensure it clears the piston front cup. The other hole is the fill hole which is a lot larger than the compensation port. Both are at the bottom of the master cylinder reservoir.
JACK
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