89 wagon brake booster check valve

[Blt2Lst]

How would one check the brake booster check valve.
When i was trying to lock up the brakes to see if they would lock up, The pedal felt a little hard and only the fronts locked. I tried this again and only the rears locked up. The ground was wet at the time and I thouught all four should have locked up easily. Could this also be a booster problem?
I recently replaced front pads, rotors, calipers and rear shoes and wheel cyclinders.
Under normal driving, they seem to work fine.
Anyone with any thoughts?

Al

[old_master]

The check valve and the booster have to do with applying the master cylinder. The master cylinder and proportioning valve affect front and rear brakes differently. There is probably air in the system, try bleeding at all four wheels.

[Blt2Lst]

That sounds like a good place to start.
Thanks

[bobss396]

If your pedal is firm and high, you don't have air in the system. You did replace the rear brakes recently. The shoes are pre-arced at the factory so they need to break in to fit your drums. Years back, most brake shoes were oversized and were ground to fit the drums, so little break in was needed. I'd give them 1000 miles or a month to break in, then do an adjustment and they should be better. On wet pavement, all bets are off on which axle stops first.

[Blt2Lst]

Is it necessary to have the car running when bleeding the brakes so the pedal goes down easier?

[maxwedge]

Try not to push the pedal to the floor bleeding the brakes with an old master cylinder, the piston seal can be damaged, I would use a hand held vacuum pump bleeder, better way.

[old_master]

I agree with maxwedge on the bleeding procedure, and no, not necessary to have the engine running. In fact, probably better to leave it off.

[silicon212]

Originally Posted by old_master

I agree with maxwedge on the bleeding procedure, and no, not necessary to have the engine running. In fact, probably better to leave it off.

MUCH better to have the engine off, and the vacuum line and check valve pulled out. You don't want any vacuum in there at all when you are bleeding the brakes, or you will have a HUGE mess to clean up afterward.

[Blt2Lst]

Thanks for the info guys.

[bobss396]

When I was doing brake jobs full time in a big shop, I usually used an Ammco pressure bleeder with the engine off.

Also we took care not to bottom out the pedal, which pushes the innards of the master cylinder past that ring of crud at the bottom of the bore and sometimes resulted in a shot master. The old Mopars were a crap shoot for some reason.

At the end we would disconnect the bleeder, top off the master, start the engine up to push the front brake pads all the way out, kill the motor, pump out all the vacuum by foot and give the fronts another shot of bleeding. I do this today at home and it works every time.

Bleeding brakes takes some finesse, at the pedal or at the bleeding wrench end. We always had favorite people around the shop for manual bleeding.

Bob