It could be something as simple they sent you a disc/drum proportioning valve by accident and it's keeping pressure applied when it shouldn't be.
Rear Disc Brake Conversion - Issues
- Thread starter G_RIDE_81
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the bleeder on the caliper is pointing in an upward direction so make sure you don't have you face in the way. If the brakes are locked up and there is pressure you could have a damaged brake line. With the presssure released your rotor should be able to turn. If there is no pressure in the line then as someone suggested look at the parking brake
Check the push rod length coming out of the vacuum booster to make sure it is not too long. A longer push rod than needed may be applying some pressure to the rear of the master cylinder piston and applying pressure in the system.
Like said earlier, check to see if the rear calipers are adjusted correctly. The rear calipers should be adjusted by engaging and disengaging the emergency brake, if the emergency brake cables are hooked up and you have a functioning emergency brake system. If it is functional, make sure that the cables are the correct length and not applying pressure when the emergency brakes are not engaged. If the emergency brake cables are too short, it may be keeping the rear calipers engaged and not releasing them fully causing the pads to drag.
If these two things are not your issue, in my opinion, it is either a old rear rubber brake line or a bad master cylinder. An old, rubber line may collapse shut when the master cylinder is pulling fluid back into the master cylinder reservoir. The collapsing rubber line will hold pressure on the caliper and may not fully disengage the pads. The 30 year old rubber lines (2 front and 1 rear) should be replaced regardless if its not the issue.
Master cylinders, even new, do not have the best reputation. I have had customers having sticking calipers and it turned out to be the NEW master cylinder after a replacement master cylinder was swapped in its place. If you are hearing noises from the master cylinder area, it is most likely the master cylinder giving you the issue and a replacement master cylinder should be installed.
Like said earlier, check to see if the rear calipers are adjusted correctly. The rear calipers should be adjusted by engaging and disengaging the emergency brake, if the emergency brake cables are hooked up and you have a functioning emergency brake system. If it is functional, make sure that the cables are the correct length and not applying pressure when the emergency brakes are not engaged. If the emergency brake cables are too short, it may be keeping the rear calipers engaged and not releasing them fully causing the pads to drag.
If these two things are not your issue, in my opinion, it is either a old rear rubber brake line or a bad master cylinder. An old, rubber line may collapse shut when the master cylinder is pulling fluid back into the master cylinder reservoir. The collapsing rubber line will hold pressure on the caliper and may not fully disengage the pads. The 30 year old rubber lines (2 front and 1 rear) should be replaced regardless if its not the issue.
Master cylinders, even new, do not have the best reputation. I have had customers having sticking calipers and it turned out to be the NEW master cylinder after a replacement master cylinder was swapped in its place. If you are hearing noises from the master cylinder area, it is most likely the master cylinder giving you the issue and a replacement master cylinder should be installed.
Weird noises, yes! Not always, but I have heard a whistle from the proportioning valve. What could this mean?
Grommet,... which one? Sorry, I didn't assemble it so not sure which you're referencing.tea time....
you have a vacuum leak, could be the grommet or the rubber line
And I'll check the rubber lines.
Wondering if the calipers were centered correctly when they were installed on their brackets. Depends on manufacturer, but most magazine installs I've reviewed make mention of having to shim the calipers in order to have them centered with respect to the rotor, Because they are solidly mounted to the brackets centering them using shims means creating or achieving an equal amount of space between the puck and rotor on each side of the rotor. Too little space could allow one of the pads to make the initial contact you mention but not be able to retract far enough when the pedal is releases so that when the second time you brake, the pad makes contact and stays there. Eventually the piston does retract enough to allow the rotor to move but it is still too close to the pad and open to locking up again.
You were correct sir!! Even though i purchase the MC and Booster as an assemble unit the rod was too long. I added a washer to the 2 bolts to create the necessary space and cut out a rubber gasket os the same thickness to keep any dirt from getting thru the gap. My ride rolls on!! Thanks everyone for the advice!! Now on to other projects.
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