1971 Body/Chassis FSM

1971-74 F Engine FSM

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Replacing the stock Booster with a Mini-Truck Booster

You will need to get a 1979 to 1985 Toyota mini-truck booster complete with all the spacers and mounting plates and the inline vacuum check valve. This valve is installed in-line INSIDE the hose that connects to the booster. Make sure to ask for it if you get one from the bone yard. Don't forget the nut/bolts/washers for everything. Your master cylinder will bolt right up to this booster but if they are throwing it in then take it. You can use it as a core for when you eventually do the disk brake swap.

I got one from a guy in Va and when it arrived here is what I found:


Fig. 1

Boosters Side by Side

With Spacer

Fig. 2

Spacer Installed

For comparision to the stock booster see Fig. 1. The booster is slightly thicker in

the body, about the same diameter, but is a good 2 inches overall longer from the front to the end of the push rod. Though the spacer that comes with it makes up most of the difference this still caused me a bit of a problem. I'll explain that a bit later.

Mounting The Booster

  1. Remove the brake lines from the master cylinder and bend them slightly out of the way.
  2. Unbolt the master cylinder from the booster and take it to the bench.
  3. Remove the return spring from the pin bushing.
  4. Remove the cotter pin from the pin bushing holding the push rod to the brake pedal arm and push the pin out to release the push rod.
  5. Unbolt the old booster by removing the 4 12mm nuts holding it in place.
  6. Remove the booster through the engine compartment.
  7. Clean up the 'new' booster by cleaning around the opening where the master cylinder bolts. Wipe it all down, then put a coat of wax on it. Just kidding!
  8. Mount the booster so the vacuum inlet is UP. Also when you mount the new booster make sure to leave all the spacers, gaskets, and mounting plates in place as shown in Fig.2-3! If you leave these off it will NOT work!
  9. Until you get everything adjusted correctly only install and tighten two nuts on diagonals from each other. You may be removing and installing it more than once.
  10. Attach the return spring to the pin bushing. You must do this to get a good reading for the pedal height adjustment.

Booster Spacer

Fig. 3

Booster Spacer


When I first mounted mine and tested it, it would not hold vacuum. (See Below for testing the Booster.) At first I thought I had a bad booster but it turned out that because the push rod was a bit too long (even when adjusted all the way against the brake pedal arm) the booster was being activated when I tightened down the bolts! (Of course it took 2 hours to figure this out and fix it.) My solution was to cut about 1/4" off the end of the push rod. This stopped the booster from being wrongly activated and allowed me to adjust the push rod to get the proper pedal height. You may or may not have to do this, mount yours and see if it holds vacuum. If it won't, first try adjusting the push rod in. If the rod contacts the brake pedal arm you will need to trim it. Start with a 1/4" and test it again. See Fig 4. for the adjustment.

Pedal Adjustment

Fig. 4

Adjusting the pedal height

Adjusting Pedal Height

  1. Place a ruler against the firewall so that you are measuring the distance from the bottom edge of the pedal to the firewall. See Fig. 4. It should be about 9.65". To adjust this loosen the 14mm locknut on the push rod and using a pair of pliers turn the rod in or out to obtain this reading. DO NOT adjust to the push rod out to the point that you have triggered the booster! Don't sweat it if you can't get it exact! I got close. Instead of 9.65" I got 9.75. Tighten the lock nut down when done.

Testing the Booster

Testing Booster

Fig. 5

Testing Booster

I tested it with a Mighty-Vac Vacuum tester and it checked out good. To test your booster hook it up as shown in Fig. 5. Pump the handle until you have about 20 inches of vacuum showing. If the booster is good it should hold that vacuum for a long time. If it's leaking then the needle will gradually fall. Make sure you have good tight connections! Don't want a loose hose causing you to throw a good booster away! :-) To test the check valve connect it in series with the booster and repeat the test but after reaching the 20" disconnect the pump. The check valve should prevent the booster from bleeding off.

Adjusting the Booster Front Push rod to MC Piston Clearance

Click here for this procedure.


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