New Booster master cylinder frustration

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barnesjtsl
Posts: 166
Joined: Fri Apr 03, 2009 2:13 pm
Your car is a: 1979 Spider
Location: Hillsboro, OR

Re: New Booster master cylinder frustration

Postby barnesjtsl » Mon Mar 26, 2018 7:13 pm

Thanks for the reply. It looks to me like the rod with the black cup out is close to 3/16 of an inch (see the picture above). The rod is screwed in as far as it will go. I thought there might be and adjustment for the fork that goes through the firewall and connects to the brake pedal but that is not the case.

Any ideal how i can get it in further? Could I possibly put a thin gasket in between the MC and the Booster?

tonym
Posts: 12
Joined: Sat Jun 24, 2017 11:22 pm
Your car is a: 1979 spider 124

Re: New Booster master cylinder frustration

Postby tonym » Mon Mar 26, 2018 10:27 pm

Could be as simple as a clogged bleeder screw? I had one in the rear that wouldn't pass any fluid. Have you completely pulled the bleeder to see if any fluid flows? I've also read that the back brakes won't actuate until the fronts have full pressure but your situation seems the opposite. Good luck, hope you solve it.

JohnMc
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Posts: 131
Joined: Mon Aug 10, 2015 8:30 pm
Your car is a: 1970 Fiat 124

Re: New Booster master cylinder frustration

Postby JohnMc » Mon Apr 16, 2018 8:16 pm

One of my manuals shows that the hydraulic piston control rod should extend out about 1.05 mm - but might not be for your year.
If it cannot I would return it. I would not put plates or spacers etc - these are your brakes.
What is pretty/fairly good about these old cars is the brakes and handling.
I had received a new power brake assembly and did not like the way the piston worked so cleaned up my old one and put it back. Might be some bad ones out there.

JohnMc
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Posts: 131
Joined: Mon Aug 10, 2015 8:30 pm
Your car is a: 1970 Fiat 124

Re: New Booster master cylinder frustration

Postby JohnMc » Tue Apr 17, 2018 11:45 am

I am not an expert on this at all.
I just looked at the new brake booster I have in a box. Playing with the hydraulic piston control rod on mine there seems to be a center point that you can push the rod back fairly far and then if you bring it quite a ways out and push it back it might not hit that correct "hole". Kind of have to move it around so that it goes in the correct hole inside the booster. Probably not making much sense but that is the best I can explain.
On mine when the rod is in what I think is the correct center hole it will go back far enough that I can adjust the end so that it is out where the specification shows.
I do not know but I was thinking that the black plastic piece was for shipping - mine also had a rubber band to keep it the rod somehow in place.
I would ask the supplier about the plastic piece. Was there a plastic piece on the one you took out?
Am sure that others can explain this better - again not an expert on this at all, but just looking at mine.

BEEK
Posts: 1799
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: New Booster master cylinder frustration

Postby BEEK » Fri Apr 20, 2018 6:58 pm

I have run int this issue myself. The boosters being sold by at least one of the vendors is not exactly correct in the fact that the rod will not adjust short enough to work properly. I made a metal flange that i bolted behind the master cylinder spacing it out to make things work. I first used washers / shims to get it to where it needed to be then made a plate. The reason I wanted a plate is i felt full contact was better than just point contact of the washers.

Now having said this I ordered another one of those not perfect fit boosters for another car and will install it the same way. The booster is perfectly fine and I am glad to be able to purchase a new unit for the price. Having to make a small adaptation for a 40+ year old car is not a big deal in my opinion
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 3 are drivers, 500L as daily driver, 500X just got for wife,
son has 78 spider


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