Brake Booster Push Rod Adjustment

[BackDoorz]

I haven’t seen anything like this in the forums and it maybe another way that everyone is doing this. Anyway, thought I would add my way.

I recently installed a Brake Booster on my 1976 280Z. When it came time to bolt up the master cylinder to the brake booster, I knew that I was going to have to make an adjustment on the push rod that goes into the master cylinder from the brake booster. If you have ever done this job, it's sort of guessing game on just how much you should turn the push rod in or out.

After looking at the whole setup for awhile, I think I have come up with a way that will get you pretty close.

- Insert a small screwdriver into plunger opening of master cylinder until it

stops.

MCPlungerMeasure1.bmp

- Make a small red mark on the screwdriver at the end of the master

cylinder that goes into the brake booster.

MCPlungerMeasure2.bmp

- Take the screwdriver and lay it next to the master cylinder.

- Line up the red mark even with the end of the master cylinder and make a

blue mark on the screwdirver next to the face of the flange (where the

bolts go through) that goes next to the spacer on the brake booster.

MCPlungerMeasure3.bmp

- The distance between the end of the screwdriver (tip) and blue mark is

how much the rod from the brake booster can go before it starts to move

the master cylinder plunger.

- Take the screwdriver and place the tip to the diamond shape spacer on

the brake booster. Compare the distance of the rod from the brake

booster against the distance from the tip of the screwdriver and the blue

mark and adjust push rod accordingly.

MCPlungerMeasure4.bmp

Notes: The master cylinder actually sticks into the brake booster up to the

flange. That is the reason for measuring from the end of the master

cylinder to the plunger. Red & blue markings are my own choice,

any markings will do. Any straight object will work for marking, I

used a small screwdriver. Make sure that push rod is pushed back

as far as it can go into brake booster.

[Jarvo2]

Thanks for the writeup! I did a round of guessing the last time I replaced the brake booster.

[siteunseen]

Yes, thank you. I have to replace on myself.

[driven]

Here is something I haven't found yet in other forums and hoped I could get some help with.  My '78 280 needs a booster replacement. My Datsun 1970-1978 shop manual says the '78 comes with a 7 1/2" diameter booster which I am learning is very dificult to come by. There are 8 1/2" diameter boosters out there. Are these different sized boosters interchangeable on the '78?

[siteunseen]

1970 through 1972 240s used the smaller ones.  280s use the big one.  A lot of 240 guys put the bigger one on the older 240s, better stopping.

 

I had a hard time replacing the small one.  A trick I figured out was to take the master cylinders loose, leaving the brake lines hooked up, tie them in place with string to keep them from falling down and bending the brake lines.  I laid a paint stir stick across the opened inspection lid, making a triangle and tied the string to that. 

 

The hardest part was the four bolts behind the clutch and brake pedal.  Maybe easier on a 280, hadn't had to do that yet.  Have fun!