Booster pushrod adjustment (1 Viewer)

[digitalmarker]

Hey all, installing a new OEM booster. The one I am replacing had a ton of empty pedal travel, among many other issues. Likely a bad MC too which I am also replacing.

I used a tool to measure the position of the MC piston vs the position of the push rod pin. There is just a slight gap between the tool and the push pin.

The pushpin on the new OEM booster is set at the same position as the old booster I am replacing. One of the reasons I’m going through the brake system is because of a spongy brake feel and a ton of empty pedal travel before the brakes engage. MC is a likely culprit, but wondering if the push pin position has something to do with the empty pedal travel.

Am I doing this right? And is any adjustment needed?

 

[Augustiron]

You're doing it right.
There's also a free play adjustment on the rod that connects the pedal arm going into the booster.
It is accessible underneath the dash and is self-explanatory. I usually take 99% of the slop out of it and just leave a little eighth to quarter inch of movement in the pedal of freeplay.
Those are the two adjustments to take up free play between the pedal and the master. If you still have spongy brakes, they need a good and proper bleeding.

 

[digitalmarker]

You're doing it right.
There's also a free play adjustment on the rod that connects the pedal arm going into the booster.
It is accessible underneath the dash and is self-explanatory. I usually take 99% of the slop out of it and just leave a little eighth to quarter inch of movement in the pedal of freeplay

Was not obviously to me unfortunately. This is what I am seeing underneath - what do I adjust?

 

[digitalmarker]

Another observation - the rod end of the new OEM booster is about 1/4” longer than the one I am replacing. The new unit itself is bigger/taller. Does this affect the positioning of the clevis that attaches to the pedal?

 

[ppc]

One of the reasons I’m going through the brake system is because of a spongy brake feel and a ton of empty pedal travel before the brakes engage.

One possible explanation for "empty pedal travel" is the the front pads have been pushed back into the caliper by loose wheel bearing. What you perceive as empty travel could just be the pads traveling excessively before coming in contact with the rotor. To check this, in your driveway, engine off, you need to pump the brakes until hard, let off the brakes for a short period of time and reapply brakes again. If there is less empty travel the wheel bearings are suspect. Start the engine and do the same test again, checking for any differences. Lastly drive the vehicle a short distance, steering right and left. If the empty pedal comes back then it confirms the wheel bearing are the cause.

 

[digitalmarker]

One possible explanation for "empty pedal travel" is the the front pads have been pushed back into the caliper by loose wheel bearing. What you perceive as empty travel could just be the pads traveling excessively before coming in contact with the rotor. To check this, in your driveway, engine off, you need to pump the brakes until hard, let off the brakes for a short period of time and reapply brakes again. If there is less empty travel the wheel bearings are suspect. Start the engine and do the same test again, checking for any differences. Lastly drive the vehicle a short distance, steering right and left. If the empty pedal comes back then it confirms the wheel bearing are the cause.

Wheel bearings are good. Recently redone and tested. I am deleting abs at the same time and replacing the MC, which are the more likely culprits.

 

[Augustiron]

The adjustment I was referring to is the clevis and locknut on the end of the booster shaft that attach to the pedal arm That you are comparing a length of in the photo.
Don't measure or compare as you are with the level though, what matters is the distance from the firewall mounting surface where the 4 studs are to the end of the threaded shaft.

I have had to cut down the threaded shaft in replacement boosters. Run a nut down on it before you cut, then take it out off and it will clean up the threads on the way out.

Measure three times and cut once.

If you want to be sure, put the booster on the firewall without the master cylinder But with the clevis mounted on the threaded shaft.
Attach the clevis to the brake arm with the pin, and then with pliers you rotate the threaded shaft going into the booster to take out the free play between the brake arm and the booster.

There's a possibility the threaded shaft will hit the brake arm from sticking through the backside of the clevis before the free play is out and then that's how much you have to trim.

I hope that makes sense