Hydroboost 4 wheel disk ISSUES !! HELP

[6600DURAMAX]

Truck is 99.9% ready for the road but I am having brake problems. Below are some details of my install.

PROBLEM: Both Rear disks calipers are sticking BAD (can barely turn the tires by hand with the rear end jacked off the ground) Brake dust covered wheels within 1 mile! Both Front disk are lightly sticking (not as bad as the rear but still sticking)

Brake history - Everything is NEW, not 1 reused/old part
Hydroboost Unit
Master cylinder
4 WHEEL DISK proportioning vavle
All new brake lines
All new calipers


My first thought is the pedal is putting pressure on the hydoboost unit but checked under the dash and the pedal is not putting any pressure.

I will confess - I did not bench bleed the master cylinder ( I was lazy) BUT I do have excellent brakes (they will throw me thru the windshield now) with a firm pedal. Could this still be the issue?

I really want this thing on the raod quickly

HELP

thanks

[grancuda]

Is the hydroboost unit matched with the proportioning valve as far as the vehicle it is spec'd for?

[Lugnut64052]

Originally Posted by 6600DURAMAX

I will confess - I did not bench bleed the master cylinder ( I was lazy) BUT I do have excellent brakes (they will throw me thru the windshield now) with a firm pedal. Could this still be the issue?

I would think that if you still had some air in the system you'd have spongy brakes rather than a hard pedal. I'm assuming you bled all four corners out until they ran clear, right? If so, you should be fine.

I'm thinking it's got to be either the master of the proportioning valve. Rebuilt masters can be bad right out of the box. Give us some details on the valve . . . . what kind? Is it adjustable?

[6600DURAMAX]

The master cylinder was bought off of a website called PirateJack (heard alot of good reviews and they had good pricing and good service). It is a chromed M/C that is disk/disk. The proportioning valve also came from them, it also is a stock type (non-adjustable) but is for a disk/disk setup. It also is chrome.

I was thinkin of pulling the back calipers off and ensuring I could get the cylinder pushed all the way back in with a clamp.? Then reinstalling.......

[jorgensensc]

I don't know if this has anything to do with it, I don't know a lot about braking hydraulics.I'm using water hydraulic thought process here. But could the size of brake lines going to the rear (being smaller than what your hydroboost is set up for) cause the rears to hang up? Maybe the pressure isn't getting released fully because the lines are smaller, so there is not enough fluid movement to return fluid back and release the rear calipers? Does that make any sense?
Just an idea.
Shawn

[6600DURAMAX]

I am using a 3/16'' line back there which I would think was enough. Might look into that idea if nothing else works.

Talked to a buddy and he has given me some more good pointers to look into first. Good tips for anyone having similar issues

1. Ensure the disk brake brackets are not causing the problem. Loosen the bracket bolts and see if that allows the calipers to loosen. Most disk brackets require shims to get the correct distance from the rotor, even .020 could make a difference.

2. Ensure the rod going from the hydroboost unit to the m/c is not applying pressure constantly. To do this loosen the 2 bolts holding the m/c on and see if that frees the brakes up. If so grind or adjust the rod accordingly.

Will try these items tonight and any others you guys can still think of.

thanks guys

[eagleuh1]

I'd bet its the rod from the brake pedal to the hydraboost. I had similar problem when I used a smaller booster on my s10 blazer. Didn't match with the original booster by about 1/8 inch after welding 2 halves together. Ground a little off and worked good

[mclairmo]

Another thought is what if they sent you a disc/drum master cylinder? You would then have a drum brake residual valve in the master to the rear brakes which would cause them to lock up or drag. Also, make sure all rubber hoses in the system are not twisted or kincked. If they are, they will act like a one way check valve, letting fluid flow into the caliper but not back out.

[ERASER5]

Originally Posted by mclairmo

Another thought is what if they sent you a disc/drum master cylinder? You would then have a drum brake residual valve in the master to the rear brakes which would cause them to lock up or drag.

That was my first thought! You do not need any residual valves for your setup.

[cparman]

I am thinking that there is not ANY clearance between hydroboost unit and the master cylinder. What I usually do is to unbolt the master cylinder, without removing the brake lines and making a mess, and see if the rod coming from the hydroboost is adjustable ( meaning it is threaded ). If it is not that is ok as well. What you want to do is to verify that you have a tiny bit of clearence between the hydroboost, and the MC. I will roll a tiny bit of clay ( 1/4 " ball ) and put it on the tip of the rod coming from the Hydroboost. then bolt ht e booster/MC back together for a minute, and then unbolt it. Checking to see if the clay is completely crushed or not. If it is the you need to adjust or trim the length of the rod, to get a scunch of clearance.
I have not done this with Hydroboost, but done it a bunch with a vacuum booster type setup