Another brake question

I have finally come to the end of my build. I'm just running down problems as they come up.
I took my 1970 jeep cj5 with swinging peddals, power brakes and disc in front and 11" drums in back for a spin around the block, (1.2miles). When I pulled back in the drive way my front brakes were smoking and glowing red. This is basically the same set up I had before I started the
I replaced all the brake lines and left the residual valves in the lines, (2lb in front 10 lb in back). I replaced the master cylinder with a brand new one that was set up for the disc/drums.
when I pulled back in garage I noticed that there was so much pressure in lines it was keeping the brake lights on.
My question is, can the residual valves be causeing this? Should I have eliminated These, since the master cylinder was already set up for the correct brakes?
I have turned to your expertise.

 

What Howard said. Check those first. Also check and see if the master cylinder is overfull. If so the fluid could be expanding as underhood temps go up applying the brakes. There should be room in the reservoir for the fluid to expand. Also make sure the brake lines are routed away from exhaust for the same reason. I would also check the master cylinder and see if it has a residual pressure valve installed for the front brakes. If so, remove one of the two that are installed.

 

Howard, yes only the front brakes are locking up. i dont have a lot of free play in the pedal (11/2"-2"). I have power bled the entire system several times. The brakes work good, they will send you through the windshield if i'm not careful.
Whats the easiest way to see if the push rod is returning far enough to uncover the front port?

 

Nick, I checked the master cylinder its about 1/2" from the top of the master cylinder. I have double checked my brake lines and they are in and around the headers on the drivers side, (close as it gets is 4"). I also check the master cylinder and it does have the residual valve installed. I'll try removing the in-line one. I will also check the pushrod to see if it is returning all the way.

 

Not sure what master/booster you're using but some have an adjustable pushrod between the booster and the MC. Not enough free play between the rod and the piston can cause the same thing.

 

Is the residual valve after market? They make a 10 lb for drums and a 2 lb for disc. Make sure you have the right one.

 

I have been overwhelmed by the holidays and work, and did not make it into the garage to work this problem out until recently. I pulled the after market residual valve , (2lb) ,out of the front brake lines and re bleed the entire system. This gave me another inch or so of pedal movement before the brakes started engaging. I drove it around the block and the brakes worked great. I then drove a little further to the gas station and started having the same problem as before. As soon as I started using the brakes the pedal became hard again and the front brakes began dragging and were glowing by the time I made it home.
I tried what Howard suggested and puled the cover and replaced with plastic wrapped and worked the brake pedal and nothing squirted at all.
In reading Pack Rat's suggestion: can I replace my push rod with an adjustable one with the stock MC? or replace whole unit? any ideas where to pick one up that would fit my application?
Any help would be appreciated.
Thanks, Rob

 

I had the same problem. Same exact problem. yes, even the brake light staying on. It was my push rod not having enough free play. Brakes were partially engaged, heated the caliper and expanded the fluid, causing the brakes to lock up. I have disk brakes all the way round but are manual. your results may vary.

 

My first guess is also that the push rod is still too long. No squirt when the brakes are released, the piston in the MC isn't traveling as far back as it needs to release the preassure in the system, As a side thought, How good is the return spring on your brake pedal?

 

I will look a little further into this, and see if I can figure it out. What source did you use for an adjustable push rod?

 

The return spring is good. I can't even pull the pedal any furth back by hand.

 

Shorten the push rod.

 

I have an under the floor manual dual master cylinder setup. I copied herms bracket. My push rod was just in a pile of junk I had, so i have no idea, but I think its from a cj2a .it has a threaded part that was too long, so i cut it off and rethreaded it. May take some fabrication skills. I pulled out my hair about my brakes. I didn't think I had any pressure, but I did. in my case I needed to have 1/2 inch of FREE play to make sure the rod was not pushing the piston in at all. Tried removing residual valves, bled brakes, etc.. got stuck twice. one time i walked to an auto parts store and borrowed a 10 mm wrench. GM metric bleeder calipers.. bled the brakes off enough to get home. good luck

 

OK!!!! I figured out my problem, (thanks to all the help here). I had a brain fart! There are 2 different rods. The 1 I kept thinking/looking at was the 1 inside the cab from the power booster to the brake pedal. The 1 I needed to adjust was the 1 from the power booster to the MC. I adjusted it about 1/2" in and my front brakes released! I drove it around the neighbor hood and the brakes work great. They stop and release. Thank you all for your help on this.