wide low profile tires for d100

[FredM]

might want to check to make sure the master cylinder is working
sometimes they are bad

[Jeffc]

agree with Fred, no peddle and no leaks has to
be a master problem.
Since your talking rotor/calipers on the front
you must have disc brakes.
I assume it pumps up with one full stroke.
Questions:
New master or rebuilt?
Did you change your rod or use a stock one
that came with your truck (peddle to master)?

[rock]

JeffC and Fred,

I was about to conclude a bad Master Cylinder, but didn't want to admit it...because it is brand spanking new. I did the uglytruckling front disc conversion and added in the Mopar proportioning valve at same time. Pumping pedal one time pumps up brakes good and vacuum at 18.5 inches works booster just fine, just the old classic foot on pedal hard leaks down a bit after a few seconds, but not to floor. I was debating to remove the proportioning valve and see if that was the problem, but it seems to make no difference whether the valve is all way to rear or all way to front discs. That combined with the leakdown spelled BAD NEW CYLINDER...rats, after all that work in bleeding, flawed from the start. It has the disc calipers mashing the front rotors too tight to turn and won't release. I had to change pushrod and drill a new hole in the pedal arm to get the right stroke for a 2 compartment master. I am getting full stroke up and down with bleeders open, so stroke is ok. What a #@@&!!*.

Thanks
rock
'64d100

[mopar400]

If I remember correctly from school you will need a small check valve in the rear brake circuit that keeps a small amount of pressure at all times on the rear wheel cylinders. If this check valve is not present you will have to pump the brakes until the rear cylinders move out to push on the shoes. Some master cylinders have these but others do not. I'm not sure how you would be able to tell. Mopar400

http://www.zigsstreetrods.com/Pages/c07936.html
http://www.totalcostinvolved.com/produc ... ProdID=215

[rock]

Thanks again guys,

Still not solved but getting closer...why not solved yet?

Well, first ya got this ingorance factor (mine). I did not know the caliper system used a LARGER port than did the drum system. My plumbing followed instructions exactly, and the instructions say to plumb up so the front port of the dual port MC goes to the front (caliper) brakes and the rear port goes to my Mopar Performance proportioning valve and then to rear drum brakes.

It turns out I was given the WRONG master cylinder, one that had the small reservoir in front of the pair of ports... a Raybestos MC39017. This MC has the large port on the rear. So my disc brakes feeding off the front port had the small port and could never work even though I followed directions exactly. How did I figure it out..wellll

After getting the new (wrong) MC I in the all new brake system I vacuum bled it, pressure bled, helper bled with me watching bleeders, bled by me with new speed bleeder screws finally installed, then bled with those screws in and me watching with a helper pushing. Each time there was air in lines. Each time I bench bled master cylinder (5 times and had air each time in rear port). Each time the master cylinder would have a rock hard stroke stop on the bench.

Finally for a little while I got the air is out of lines and wheel cylinders and calipers, but with all bleeder screws closed the brake pedal went halfway to floor to start and leaked down a bit on steady application. So I convinced myself the MC was bad and took it back. They said "uhhhh, that isn't the right cylinder, you need a Raybestos MC36306" and sure enought it had the large port on front and small on rear! Go back, same problem, same process, same result, bad MC. Now remember these are NEW! So back again, this time order (7 day delivery) NEW Genuine Factory part, not a Raybestos and in meantime find a link on the web that reports these Raybestos MC's are known to be be bad out of the box!

SO here is hoping this time, and if I now need to go the check valve route, that can't be much more work!

Stay tuned for messages from the slightly less ingorant but wallowing with skeeters in 90+ degrees!
rock
'64d100