Brake booster adjustment is impossible?

[barnesjtsl]

I bought a new booster and master cylinder. The adjustment for the booster plunger from what I can tell is less than 1 millimeter. I bought a new booster from Vicks and with the plunger screwed in all the way with the locking nut all the way down (I can't get the plunger to go in any further) it sticks out about 3/16 of an inch. It won't go in any further.

See the picture below. It shows the master cylinder installed without the reservoir hoses and brake line tubes connected. I filled the master cylinder reservoir intakes and as you can see the single outlet for the rear brakes fill's up but the two for the front the reservoir intake fills up but nothing appears in the outlets for the front brakes.

When I had the master cylinder on the bench uninstalled I filled the two reservoirs and all three outlets filled up and started to overflow. After installation I do the same thing and nothing comes out the front brake outlets.

Is this because the booster plunger is sticking out too far?

This is my second time doing this with the same parts. The first time I bench bled the master cylinder in the vice. I "bench" bled the mater cylinder in the car still nothing.

Again, I can't get the plunger in any further. Could I possibly put a gasket between the master cylinder and the booster? That would bring the master cylinder farther away from the plunger? This is really driving me crazy. I've been dealing with this for two weeks now. Any ideas.

John

[kmoses]

If the brake booster actuation rod lock nut when installed causes the rod to extend to far, remove the lock nut and adjust the rod until the actuation rod extends out as far as the old unit. Confirm that your master cylinder works properly, then unscrew the rod, apply loctite to the threads and screw the rod back into the proper position.

[barnesjtsl]

Thank you kmoses for the response. That sounds like a really good idea. Is this something that you have done before?

Thanks again,

John

[spider2081]

in addition to what "kmoses" stated its always a good idea to compare the piston cup of of the old and new master cylinders where the rod contacts the master cylinder. They can differ depending on the brand of part.

[kmoses]

I did have to remove the actuator rod lock nut on mine and use loctite and if I recall correctly, the mounting studs on my booster were about 1" or 1 1/2" longer than the one I took off. I cut them off with a hacksaw and dressed the ends with a file. The brake booster has worked great but like other fiat spider replacement parts, some fitting is required. Just wait till you replace your heater core, valve and hardlines!

[tima01864]

The plastic piece in the photo, Does that get tossed or installed?

[faulknerrs]

The plastic piece in the photo, Does that get tossed or installed?

The plastic cup stays. Confirmed this today, May 13, 2019, with Auto Ricambi.

[DieselSpider]

Many resolve this by simply installing a shim plate between the booster and the master cylinder.

[FLCharles]

John,

Did you solve this yet? If so what did you do?

Regards,
Charles