I have a 1971 Comet change to disk brakes front and back. I am having problems with no paddle the first push. I used the 1978 Gm Calipers front and back with Manuel E-brake built into the calipers Power booster/Master Cylinder/Prop.Valve kit. Bleeding lines a lots times no air in lines. Has anyone had this problem. Thanks Sam.lanham@att.net
The master cylinder is 1978 GM came as a kit from Rod & Custom Motorsports Inc. there # RC-138. They sent me another master cylinder & Prop. Valve not any better. The first valve when I tested with test light was not working right. I was told if the light was on it was not right. The new one the light is off when I tested it. They sell parts for Mercury's & Comets. Thanks, Sam
I used a 1978 GM Power Booster/ Master Cylinder/Prop. Valve Kit from Rod & Custom Motorsports Inc. there # RC138. They sell Mercury & Maverick Parts. Thanks Sam sam.lanham@att.net
Did you install a residual pressure valve to the rear brakes?? Does the master cyl have an integral residual pressure valve??
It has a GM combination valve mounted under the master cylinder this suppose to be all it needs for back and front disk breaks. I also add 2lbs valve at the back tee at Axel. Thanks Sam
Sounds like lack of volume from the master cyl or its defective... Pedal ratio needs to be correct as well but that wont cause lack of peadal on the first push. Does the peadal pump up and get firm, giving you good stopping preformance???
The pedal goes 1/2 way down when it is pump up. After a little while it goes 3/4 way down. The master cylinder & prop.valve they sent to me doesn't seem any better. Thanks Sam
I think you have a bad master cyl...But...I gotta ask...Do you have the calipers on the proper sides of the car??? If not, this could explain your problem.
I was going to ask the same question. Make sure the bleeder screws are at the top. If they are at the bottom, you'll never get it to work.... Trust me, I've seen it happen before. Just had to swap calipers from side to side...
Yes the bleeder screws are at the top or at 10 a clock. I have even rotated it from 10 a clock to 12 a clock. I was told some time on the back this is what you have to do. Keep in mind this is the second new master cylinder they have sent me along with prop.valve trying to solve the problem. I think it is the back brakes that is giving problem. Do you what size the hard tubing 3/16 or 1/4 sould be for back disk brakes? Have braided 4 AN from hard lines to Axel and a cross to calipers. I have also been told that I may have to adjust the e-brake to push the caliper piston closer to the pads to help. This has been a real task. Thanks very much for everyone's help maybe will we hit on the right thing. Sam
Pull the "E" brake and pump up the pedal...This will adjust the pistons out on an integral E brake caliper. Then see how the pedal feels. As for line size...That is dependent on several factors...M/C bore size, Caliper bore size...It all comes down to the volume needed to support a given amount of pressure. If you dont have air in the system and all the components are properly sized. You have a malfunctioning component. You have a bad M/C or a caliper piston/slider hanging up not allowing proper travel of the caliper or piston(s) Unless the pistons are large by huge, you dont need bigger than a 3/16ths line to supply them. Allways bench bleed a new M/C before installation as well. Bleeding em mounted in the car will damage the pistons in the M/C due to too much stroke from the brake pedal on a basically "Dry" M/C bore. Its also possible your flex lines are not up to the task and are "ballooning" on brake application. Also...Make sure none of the brakes are hanging on after you take your foot off the brake pedal... If this is the case...You have a bad hose/caliper piston sticking in its bore or a residual pressure valve hanging shut after brake application. Might be time to get brake pressure test kit and see what you are getting at each wheel as well as both circuits of the M/C...Good luck man!!! PS: Allways remember, just because the parts are new, does not mean they are good.
