brake booster push rod adjustment
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
For the rod going into the back of the master cylinder, it has a small amount of adjustment. The pushrod that actuates the master cylinder must be properly adjusted. There should only be a slight clearance between the booster pushrod and the master cylinder push rod. If it pushes on the master cylinder when bolted together, it will preload the master cylinder. This could cause the system to build pressure - that is not released - and the system could eventually lock the wheels. Too much clearance will cause excessive freeplay in the pedal. You can measure it if you have the tools, but I just usually move it out until I feel resistance, then turn it back in a tad.
Last edited by 74modified; Nov 25, 2014 at 05:59 PM.
Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
For the rod going into the back of the master cylinder, it has a small amount of adjustment. The pushrod that actuates the master cylinder must be properly adjusted. There should only be a slight clearance between the booster pushrod and the master cylinder push rod. If it pushes on the master cylinder when bolted together, it will preload the master cylinder. This could cause the system to build pressure - that is not released - and the system could eventually lock the wheels. Too much clearance will cause excessive freeplay in the pedal. You can measure it if you have the tools, but I just usually move it out until I feel resistance, then turn it back in a tad.
OK...... BUT........... HOW do I turn it out just a "BIT" ???
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
There is NO adjustment on the booster rod in the booster you have for your car. The earlier design DID have an adjustment. But yours is what it is....and that is assuming that the rod is the correct length .
DUB
DUB
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
DUB is right - 77(I believe) and above is a non-adjustable push rod. 78 for sure - mine is one of them. 
It's like a 1/4" thick rod with a ball-tip and maybe 1/8" OD on the flat side. Ball-tip goes towards master cylinder.
It's like a 1/4" thick rod with a ball-tip and maybe 1/8" OD on the flat side. Ball-tip goes towards master cylinder.
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
OK guys, you got me - I wasn't thinking about the later models (even though that is what he asked). All the C3s I have worked on had the adjustment. I have seen (on other cars) the wrong rod setup happen when swapping in a new master. You should be able to tell if the rod is too long when you install the master.
http://priorautomotive.com.c1.previe...s_PushRods.htm
http://priorautomotive.com.c1.previe...s_PushRods.htm
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Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
OK guys, you got me - I wasn't thinking about the later models (even though that is what he asked). All the C3s I have worked on had the adjustment. I have seen (on other cars) the wrong rod setup happen when swapping in a new master. You should be able to tell if the rod is too long when you install the master.
http://priorautomotive.com.c1.previe...s_PushRods.htm
http://priorautomotive.com.c1.previe...s_PushRods.htm
ok, thx
Team Owner
Joined: Jun 2000
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From: Southbound
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Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
I've got one on order BUT the one on the car is not the original....... so I don't know if it was "the correct one" when it was installed...
therefore it "may" have been adjusted at that time and "may" have to be adjusted again on my install of the "correct" master cylinder... 
I guess I will find out when I get my cylinder ..... 
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
Posting photos of the booster where the master cylinder attaches showing the rod and the backside of the mater cylinder would be great help. We can not see what you have...so it is hard to tell you any more.
DUB
DUB
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Booster and master should be a matched set. If you have a late master you need a late booster, vice versa.
If you have no idea, I'd get a matched set for your car. Bleeding master is pretty easy.
If you have no idea, I'd get a matched set for your car.
Bleeding master is pretty easy.