Sticking front brakes

[phred]

The front brakes on my 74 are sticking. Chevy disc conversion w h-boost. The system has been on for 4 years and has been flawless. I drove it last week and the front brakes are stuck. I cranked the truck pushed the pedal and checked the booster. I took the master cylinder loose from the booster to make sure the pushrod was not stuck and it made no differnence. I loosened th e bleeder screws and no fluid squirted out unless the pedal was depressed. I took of the calipers and everything moves freely, yet as soon as you press the pedal, With the engine on or off the calipers stick.
Could the splitter H-block be stuck and not let fluid back to the master therefore keeping the calipers under load?

 

[bronconut73]

If you are using the stock drum h block there is nothing in there to get stuck. It "is" just a just a hard line distribution block
It could be calipers sticking on the knuckle now that the pads have worn down (4 years of use).
So check and see if you still have clearance. If not you could just throw some new pads on it. Or grind a little more off the knuckle.

 

[76Broncofromhell]

If you are using the stock drum h block there is nothing in there to get stuck. It "is" just a just a hard line distribution block
It could be calipers sticking on the knuckle now that the pads have worn down (4 years of use).
So check and see if you still have clearance. If not you could just throw some new pads on it. Or grind a little more off the knuckle.

I thought the exact same thing: calipers hitting the knuckle or something mechanically keeping the caliper engaged.

 

[broncnaz]

X3 sounds like the calipers are hitting the knuckle. Some of the conversion brackets will flex a little with brake pressure as well so even if it appears to have clearance the flex can change it so it doesnt clear.
Also as was said The H bloock will not block off fluid flow even if it is stuck.

 

[phred]

I pulled the calipers and everything seems to clear. These pads only have 5000 miles on them. Could moisture cause this it has been raining everyday fortune past 2 months. I'm really puzzled because my 78 bronco is doing the same thing. I've space out the h boost and master cleaned and greased the slides. Clearanced the calipers and knuckles. Two trucks two different brake systems doing the same thing

 

[broncnaz]

Cant really speak on the 78 bronco as the brakes are a little different. But like I said the GM conversions to tend to flex and cause caliper bind if there is not enough clearance between the caliper and knuckles. I;d just double check the clearance maybe even paint the surfaces then drive and recheck just to make sure they are not touching.
Its always possible that the caliper pistons or even the MC piston have corrosion on them and are sticking. Its recommended that brake fluid be changed out something like once a year or every two years. As brake fluid attracts water. The older it is the more likely it is you will have moisture in the system.

 

[jckkys]

Are they both sticking equally? A mechanical obstruction on both sides at the same time seems unlikely.

 

[phred]

jckkys Yeah both are sticking which makes me think they are not rubbing on the knuckle. I'm leaning towards moisture in the calipers casing the pistons to hang. Neither truck has been driven much this summer. Working too much and bad weather.
The calipers are lifetime warrantied so I'll swap them out for new and see if that makes a difference.

 

[Deano]

Has the rubber line from the frame to the axel collapsed or got pinched or a hard line been smashed? Have you Halled them or towed them?

 

[phred]

Lines are all new and the truck has not been towed.

 

[jckkys]

A friend got a new E150 van that had a brake hose with a rubber liner that separated and became a one way valve. It was only on one side so those pads and the rotor were wearing out quickly and the dealership was clueless for months. They only found it when they replaced everything to that wheel. Try another hose from the frame to the axel.

 

[Broncofan76]

phred - Thought I'd find you here.
I'm subscribed as I want to see what this ends up being as well. Looks like replace calipers and go from there? ttt