[jayd_2]

I've got a 1937 Dodge pickup setting on a 1989 S10 Frame.

The trucks got over 7000 miles with no braking problems until last week when the front brakes started dragging slightly. They start dragging after heating up, no problems when cool. When they start dragging I can jab the pedal a few times and they will release. After the brakes cool slightly there is no excess drag. The master is a Corvette style dual so if the pedal or piston were hanging up then the front and rear should be dragging. Both front brakes have an equal amount of drag and there is no pulling left or right when the brakes are applied.

I thought it might be the residual valve but it's several feet from the calipers and not affected by heat. I could see one caliper dragging because the piston was sticking but both have the same amount if drag like the pressure is not being released completely.

Stock disc up front
2001 Blazer rearend with disc
Corvette style dual master cylinder-mounted under the floor with 8" booster
Front 2lb residual valve
Rear 2lb residual valve with proportional valve
All new steel lines
All new flex lines

[aosborn]

You might check the pushrod clearance between the booster and the master cylinder to see if it is a bit too tight. With a proportioning valve in the system the pedal pressure could be affecting the front more than the rear, especially if the dragging is minor.

Regards,

Andy

[Pantaz]

I usually find dragging caused by dirt build-up around the caliper pistons. But you say this is only happening after the brakes get warm. Perhaps it's brake fluid contamination? Couldn't hurt to flush and refill the system.

[BigEsGarage]

Ck the Bleed hole in the master for the affected circuit.
If this hole is plugged it can't compensate for fluid expansion, from heat, or pad wear and the only place the pressure can go is the caliper pistons.
It would cause these symptoms for sure.
Just a guess, and yes it can affect one circuit and not the other.
I'd still do what aosborn said an ck the push rod too.

[jayd_2]

It was the pushrod clearance. I can't figure out why it took so long to be a problem. I jacked it up when the brakes were dragging and less than one turn of the MC mounting nuts was enough to release the pressure.

[jayd_2]

Well it looks like it wasn't the pushrod length because it did it again today. I stabbed the pedal a few times and it was ok the MC piston must be sticking a little, will be replacing it next.

[BigEsGarage]

I can't stand that, you think you got it an Bam, nope not it.
Have you cracked open one of the bleeders, when the brakes start to drag?
Just to see if it is in-fact something up line causing your problem?
How do you know it's not the residual valve?
I'd even crack open the fitting at the M/C to narrow things down.
Like, if you did and found too much or pressure at X then you'd be sure.
Know what I'm saying...

[jayd_2]

Originally Posted by BigEsGarage

I can't stand that, you think you got it an Bam, nope not it.
Have you cracked open one of the bleeders, when the brakes start to drag?
Just to see if it is in-fact something up line causing your problem?
How do you know it's not the residual valve?
I'd even crack open the fitting at the M/C to narrow things down.
Like, if you did and found too much or pressure at X then you'd be sure.
Know what I'm saying...

The residual valve was my first thought even picked up a new one. I was sure it was the pushrod because the brakes released when I loosened the MC mounting nuts. I'll try cracking a fitting on the MC since both wheels are dragging.

I've had brake problems ever since cheap import parts took over, had 2 brand new Oreillys wheel cylinders fail on one car and a pressure switch fail on this one both resulting in brake failure. When I installed the Blazer rear end on this ride I rebuilt both calipers and both dragged because the O-rings where too large making the pistons stick.

[jayd_2]

Ok, I've replaced the MC, front calipers and added an ever stronger return spring but still having some issues. After a few stops the brakes "pump up a little" less pedal travel. If I stab the pedal hard the problem goes away. There's not as much brake drag as before but there's still more than I like.

A few months ago I did replace the original 7" dual booster with a new 8" dual booster, they're both the universal style with the same bolt pattern.

Anyone ever heard of a dual booster hanging up?

[enjenjo]

Check the adjustment of the pushrod from the booster to the master cylinder.

[jayd_2]

There's about a 1/32 space to be sure it was not touching when released.

[Bonneville462]

Loosen the top caliper mounts to the spindles when hot and see if they release.. I had to slightly shim the top mounting bolts on my scarebird mounts...

[jayd_2]

I finally figured out the problem, it was an 8" dual booster I had installed before replacing the rear end. At first I did not have any problems but after awhile the front brakes started dragging.

I'd contacted the company that sold me the booster and their tech said there's no way it was the booster.

A few weeks ago I decided to put the 7" dual back on and the problem went away immediately.

The 8" booster was purchased off ebay from "gonefishing69", their customer service is the worst I've dealt with ever! I've called them several times about the problem they finally agreed to sell me another booster for $30.00, they stated that "several people were sending them boosters from salvage yards for refunds/returns”. Even though I had proof of purchase they would not replace the booster, even though it's only been 4 months, the problems actually started about five weeks after receiving it.

I do not recommend purchasing any items from "gonefishing69" on ebay.