Diesel Place banner

1 - 14 of 14 Posts

·
Registered
Joined
·
66 Posts
Discussion Starter #1
I just installed a new hydro booster and it was working great. but after every thing got warm, the breaks began locking up. I figured I'd need a flat bed to take it back home. After an hour the pressure relaxed and I drove back to the house. As I got almost back to where I started the breaks began to tighten up again. Is this a tempture problem? Bad booster? Bad installation?
 

·
Registered
Joined
·
5,592 Posts
What does the pedal do or feel like when they are locked? How about the steering? Did this locking slowly come on itself while just driving or does it happen a little with each stop? What was the original issue that caused you to replace it in the first place?
 

·
Registered
Joined
·
66 Posts
Discussion Starter #3
Hi 57
The old booster was leaking. The steering feels fine. It seems to just set the breaks slowly,,,a little more as it drives. I looked at some of the old post questions and some had a problem with the length of the rod inside the booster. I used the rod from my old booster so it may not be the problem. It just seems to build pressure as I drive. If I have any thoughts,,,It seems like a valve is sticking as the booster warms up.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #4
Hi 57
I guess the steering dose feel a little sluggish, sort of a slight pulse.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #5
And the peddle feels very solid...almost too stiff. Not like before I changed the booster.
 

·
Registered
Joined
·
680 Posts
What you describe sounds to me like the actuator rod between the booster and master is slightly too long. The rod being too long is not allowing the master piston to completely retract after each application of the brakes.

As you drive and periodically apply the brakes the pressure is not allowed to completely return to the master. After a few brake applications the pressure is built up enough that the brakes are completely locked. When the vehicle sets for a while the pressure has enough time to slowly bleed off.

Next time you drive somewhere take a wrench with you. When the brakes lock up crack open a bleeder valve and see if you have pressure built up. If you have pressure built up then check the actuator rod.

Don
 

·
Registered
Joined
·
4,289 Posts
Cannon is correct-- the rod keeps the mastercylinder piston in a little bit, and that blocks the fluid return port in the mastercylinder. When the fluid gets warm and expands, there is no where to go, so it starts applying the calipers, and the brakes drag.

In the brake booster there is a washer that is suppose to keep the pushrod centered as it goes into the mastercylinder. Some have this washer missing, so when you put the masterclyinder on, the push rod is down and not centered in the piston. Remove the mastercylinder--[no need to remove the lines] from the booster and check that part.

Jerry
 

·
Premium Member
Joined
·
17,931 Posts
Why would you open a brake line and risk adding air to the system?

The master cylinder is partially applied.

Next time this occurs, loosen the two nuts that hold the master cylinder to the hydro-booster. Should take just one to two full turns, per nut. The brakes will release, and then you can tighten the nuts back up again.

Then read this http://www.dieselplace.com/forum/showthread.php?t=378808&highlight=master
 

·
Registered
Joined
·
1,593 Posts
why? too see if there pressure in the system if the fluid shoots out than theres pressure in the system
 

·
Premium Member
Joined
·
17,931 Posts
The same result can be achieved by simply loosening the master cylinder from the hydrobooster with NO fluid loss, either brake fluid or power steering fluid. It also proves that the master cylinder is the source of the brake fluid capturing/ holding.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #11
Thanks guy's. This all makes sense. I just figured it was a booster problem. but it's not, the booster rod is creating a master cylinder issue. Its always easy to cure a problem when we know what's is wrong........the rod length is critical..
You guys rock............ Dave............. Miami Fl.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #12
I put thick washers for a spacer between booster & master cylinder. It felt better but after a drive it still wants to drag the breaks. I'm thinking it must be something more valve related.
 

·
Registered
Joined
·
4,289 Posts
Cannon is correct-- the rod keeps the mastercylinder piston in a little bit, and that blocks the fluid return port in the mastercylinder. When the fluid gets warm and expands, there is no where to go, so it starts applying the calipers, and the brakes drag.

In the brake booster there is a washer that is suppose to keep the pushrod centered as it goes into the mastercylinder. Some have this washer missing, so when you put the masterclyinder on, the push rod is down and not centered in the piston. Remove the mastercylinder--[no need to remove the lines] from the booster and check that part.

Jerry

Did you check this--???
 

·
Registered
Joined
·
66 Posts
Discussion Starter #14
Good morning Jerry....Thanks for the thinking....but yes... the rod was centered by plastic disks in the back of the booster...and bay a star washer type thing in the front. I'm changing the unit, I think something is not right with this one.
Dave
 
1 - 14 of 14 Posts
Top