1988 Toyota pickup 2WD, 460K miles
After brake failure several days ago, I diagnosed the problem as a defective brake booster.
I replaced the brake booster in my old pickup. Now, the brake pedal doesn't move. It is frozen.

I set the linkage to match the original. After I connected the linkage to the pedal, the booster did not seat easily against the firewall; it stood about an inch off the firewall. When I tightened the nuts, the booster pulled against the firewall.

When I reinstalled the master cylinder, I had to push the master cylinder to get the nuts onto the screws.I did not disconnect the brake lines from the master cylinder to save an extra step.

Do any of you have any idea what I did wrong or how to correct this condition?

 

did you adjust the pushrod?

 

No, I did not. In the YT videos I watched, nobody adjusted anything.
Last night, I tried to test drive the pickup in the driveway. It wouldn't move. I guessed that the system was pressurized.
Today, I bled the brakes. About 3 ounces. My test drive in the driveway was successful. The pickup rolled and stopped right now. It feels strange: the pedal is now very high.

I wondered where an adjustment might enter the picture. If I loosen the nut on the pushrod, I can then rotate the pushrod toward the linkage to lower the pedal. Terrific.

Thanks for your question.
EDIT. Or should I adjust the preload on the pin that extends into the master cylinder?
2nd edit: Eureka. I gots to adjust both ends to move the pin almost flush with the front of the booster.

 

There’s a measuring tool for setting the push rod. You can get knock-offs pretty cheap on line.

 

Thanks. I have seen them.
Question. Should the push rod be unloaded when the pedal is not depressed?

 

I remeasured the pertinent dimens of the master cylinder and checked the protrusion of the pin from the face of the booster.. I have about 1/16" gap.
I went for a test drive. The pedal is high and has a very short stroke to begin braking, which is immediate. Probably better than new.
I can learn to live with the new pedal height.

 

Here's a short, but well-done video on the adjustment using the right tool.

 

Thanks. I had to get 'er done. It's done. Works well.

 

Well. almost done. I first had negative clearance (preloaded, not so good) and then I had probably too much clearance, as judged by the soft pedal.
So. I resorted to the Toyota manual (page BR-12 of 1988 truck manual), which says about the clearance: the sliding pin of the SST should touch the pushpin lightly, unlike some YouTube videos which suggest 0.020, 1/10, 1/16, etc.