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I think you're right D....On a hydro-boost system when you press on the pedal & it will go all the way to the floor and then the pedal will "bounce" while your holding it down.

If the pedal is going to the floor with very little pressure & doesn't bounce it may be a bypassing master cylinder.
If the op retracted the pistons without opening the bleeders it's possible he trashed his master.....

If the van is new to him, then he probably isn't use to the system.....If he's had the van for a while a now it "seems different" I would be tempted to put a master on it....

If the pedal is going to the floor with very little pressure & doesn't bounce it may be a bypassing master cylinder.
If the op retracted the pistons without opening the bleeders it's possible he trashed his master.....

If the van is new to him, then he probably isn't use to the system.....If he's had the van for a while a now it "seems different" I would be tempted to put a master on it....

i didnt open the bleeders but i've done hundreds of brake jobs without opening the bleeders...never once had a problem doing it that way. the van is not mine, but the pedal was the same before and after (except the fact it stops better and the pedal is a little higher because of the new brake pads). as of now im going to leave it how it is...truck stops fine. very weird though!

Glad to hear everything is working good for you... Since the van isn't yours, this makes sense. If you haven't done too many of these units its a common mistake since on a normal hydro-boost system you can get the pedal to go all the way to the floor with a little force



i didnt open the bleeders but i've done hundreds of brake jobs without opening the bleeders...never once had a problem doing it that way.
On stuff like this you aren't going to get a problem everytime. If people did then no one would be doing it. The problem is, is that it only takes once to take out a master or ABS hydraulic unit. When you retract the piston without opening a bleeder, you are forcing fluid backwards thru systems that weren't designed to have fluid flow in that directions. Plus if you have ever looked at the condition of the fluid that is in the caliper, that would be another good reason to open a bleeder, it's dirty and black from all the heat and you are pushing that fluid back into the system. It's better to remove it and replace it with clean fluid. Not to mention it also makes it easier to retract the piston. It's kinda the same as when a guy says that he likes to pull a battery cable to check the alternator with the car running. He's not going to have a problem everytime but alls its takes is one surge to wipe out some expensive modules.... But it sounds like all is good and you are thorough enough to check your work & not let a problem go and that is a very good thing... Have a good weekend...

What do you mean by lock up?
Does the wheel skid when stopping? Does the ABS kick in. Do the brakes hold and not release?

this started, just after i had a new transmission instaled. 1 problem after another. im wondering if the trans shop might have not pluged something back in properly that they had to take loose.

There is nothing electric that can cause that. Which wheel is doing it?
Does the truck have 4 wheel ABS?

yes 4 wheel abs. both front wheels. if it were pulling to one side, that would make more since. but its both. and it does'nt do it every time. but it is doing it more often.

That could be a master cylinder problem but the ABS should be preventing the locking up from happening. I assume the ABS light is not on.
Is this vacuum assist or hydroboost?

no, abs light is not on. and no abs codes. thats why im confused. the abs should stop the lock-up, but it isnt. but the fact that it does'nt do it every time leads me to belive it may be the abs board. id like to belive it is'nt, thats expensive. i dont want to replace it if im not sure, that, is, what it is. thot maybe the back brakes might not be working proper, putting to much stress on the front brakes, but the ABS should still keep lock-up from happening.

I really have doubts if that truck is equipped with 4 wheel ABS. The system goes through a self test every time the key is turned on so you may have rear wheel only ABS.

Have you checked the rear brakes to rule out seized wheel cylinders? For a vehicle this old its possible.

if the rear wheel cylinders are seized up they won't move to engage the brakes and the fronts will be the only ones generating braking force.

yep, both rear wheel cylinders were leaking, rear brakes wer'nt workin at all. prob fixed now. thanks.

Glad to hear you got it going again. Thanks for posting the fix.

rear wheel seals are leaking. saturating the pads. thier not working at all, so now i get to take the diff apart and pull the wheel hubs out. fun fun. hope this fixes it. i'll let ya'll kno. thank you and god bless.

its a vacume power booster. if the master cylinder was bad ? would'nt it do it every time? and if its supplying to much fluid pressure, should'nt the ABS regulate that, and interupt it ? thot thats what they do.

the wheels slide, the brakes release after you let up on the pedal. no holding. they'll slide even if its moving slowly. so its not the hoses.