greyghost79

I'm installing a new master cylinder soon on my '79. If it becomes necessary, how do I adjust the brake booster push rod?

Shark Racer

No adjustment on those - if it's too big, cut it down to size. If it's too small, buy a longer one.

74modified

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.

greyghost79

OK...... BUT........... HOW do I turn it out just a "BIT" ???

DUB

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

Shark Racer

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.

greyghost79

Hmmmm...... ok.......... so if I install the master cylinder and the push rod is too long.......... and then the brakes lock up........... uh, what's the solution ???

74modified

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

greyghost79

ok, thx

Easy Mike

Getting the correct master cylinder for your car.

greyghost79

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 .....

DUB

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

Shark Racer

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.