70 Power Brake Adjustment

[Bill L.]

The brake lights work but only when I hit the pedal pretty hard and I have to press harder than under all normal braking situations to get them to come on.

I have the clevis and nut adjusted all the way to where they bottom out on the push rod. The brake light switch is also at the end of its adjustment.

What does the nut look like on the push rod? I was thinking maybe it should be a thin nut instead what appears to be a regular size nut. It appears that there is only maybe a 1/4-3/8" of adjustment even with no lock nut.

Is it possible there should be no lock nut? The AIM does show a lock nut.

Does the actual push rod screw into the booster further? Can I still adjust the clevis once everything is assembled by removing the clip and pin?

The booster, master cylinder, and brake pedal are all original to the car. All have been rebuilt including rebuilding the brake pedal and clutch pedal assemblies.

Obviously this is a safety concern. Brakes work fine with excellent feel just no brake lights under normal driving conditions.

Thanks,



Bill

[Thomas H.]

Re: 70 Power Brake Adjustment

I'd go after the brake light switch. Even though it "works" it may not closing properly as the brake pedal moves. If I remember correctly, it should operate the lights with very little plunger movement as the pedal moves away from it.

Tom

[Bill L.]

Re: 70 Power Brake Adjustment

Thanks Thomas.

Wish I had a spare to test with a meter. That is a good thought.

The existing switch has to move at least 1/4" before the brake lights come on. I just went out and checked after seeing your post.

Hopefully someone can confirm that very little plunger movement is required to activate.

Changing the switch would be pretty straight forward.

[Thomas H.]

Re: 70 Power Brake Adjustment

There should be up to about 1/4 inch of free play in the pedal. My C3 is not at the house, otherwise I could give you a better information as my car also has power brakes.

Is the bracket that the switch mounts to adjustable in anyway?

I'm sure you will get some more definitive answers shortly.

Tom

[Jim T.]

Re: 70 Power Brake Adjustment

The brake lights work but only when I hit the pedal pretty hard and I have to press harder than under all normal braking situations to get them to come on.

I have the clevis and nut adjusted all the way to where they bottom out on the push rod. The brake light switch is also at the end of its adjustment.

What does the nut look like on the push rod? I was thinking maybe it should be a thin nut instead what appears to be a regular size nut. It appears that there is only maybe a 1/4-3/8" of adjustment even with no lock nut.

Is it possible there should be no lock nut? The AIM does show a lock nut.

Does the actual push rod screw into the booster further? Can I still adjust the clevis once everything is assembled by removing the clip and pin?

The booster, master cylinder, and brake pedal are all original to the car. All have been rebuilt including rebuilding the brake pedal and clutch pedal assemblies.

Obviously this is a safety concern. Brakes work fine with excellent feel just no brake lights under normal driving conditions.

Thanks,



Bill

How did your brake lights work before rebuilding the brake pedal and clutch pedal assemblies? Perhaps what was removed for this rebuilding was not reinstalled correctly.

[Bill L.]

Re: 70 Power Brake Adjustment

HI Jim,

I cannot remember since it was so long ago.

It is a pretty straight forward rebuild. The bracket for the brake light switch is held on by two bolts without slots. I just replaced the bushing and lubricated since I had the booster out which holds the assembly to the firewall. I reused the original spring as is fine.

I saw in the archives where some C2s have a push rod that is adjustable. I am was hoping someone would chime in with the lock nut thickness and whether or not the push rod is adjustable.

The free travel for the pedal seems okay.

Bill

[Paul O.]

Re: 70 Power Brake Adjustment

Bill

I agree with Tom that most likely it is the switch that is your problem. The switch is rather inexpensive should be around $7 to $8 at the most. My friends failed this summer on the way to Novi. I would swap that switch before any adjustments are made.

Paul 18046

[Terry M.]

Re: 70 Power Brake Adjustment

I believe the brake light switch is self adjusting, like the door alarm pin switches. Install the switch and pull back (up) on the brake pedal. The switch adjusts internally. You might try that with your old one as a first step.

[Bill L.]

Re: 70 Power Brake Adjustment

I am pretty sure the free play is correct so I am going to try a new switch.

The plunger on the switch seems to have to be all the way extended to activate brake lights.

[Monte M.]

Re: 70 Power Brake Adjustment

Bill,

If nothing else works....

Quite often there is a little end play in the plunger from the power brake booster to the master cylinder. When people rebuild the units they typically adjust the rod on the front of the power brake booster to have no end play.
This would activate your brakes just a little sooner than they would have activated before. An 1/8" inch in the power brake plunger could translate to as much an 1" of movement in the pedal.

This MIGHT be one explaination for the brakes activating a little sooner and the brake switch not tripping as soon as it did before.

I ran into this situation a number of years ago. With everything being new, it removed any end play that let the pedal contact the pedal at a lower point.
Monte

[Bill L.]

Re: 70 Power Brake Adjustment

Thanks Monte,

How would one adjust the plunger?

[Bill L.]

Re: 70 Power Brake Adjustment

The switch appears to be working fine.

I am pretty sure that I need to adjust the plunger. When bolting the MC to the booster I remember the booster plunger was already in contact with the MC piston face.

What is the best way to adjust the booster plunger on the car? Can I make the adjustment without disconnecting the brake lines from the MC?

Thanks,


Bill

[Monte M.]

Re: 70 Power Brake Adjustment

Bill,
Off the top of my head I cannot remember if you can do the adjustment without disconnecting the brake lines. The best way to do it is to remove the nuts from the master cylinder and see what kind of room you have to work with.

The fact that you remember the plunger being against the piston in the master cylinder makes me think you are on the right track.

I wish I could tell you that you could do it without removing the brake lines, but I would rather tell you the truth.

What I have done in the past is take off the passenger side tires. Depress the brake pedal a bit to close the pads/caliper. Get a "C" clamp and clamp the caliper in position (so the fluid does not run back into the master cylinder). Then you can remove the brake lines with no problem.

After you are done working on the master cylinder, remove the clamp and it will push any air in the lines along with the extra fluid back into the master cylinder. There is no need to re-bleed if done this way.

If I was not clear, PM me and I will send you a detailed list to follow.

Best of luck,
Monte

I actually have a set of small rubber blocks that I put between the caliper and the pad instead of using "C" clamps. It does the trick just fine.

[Bill L.]

Re: 70 Power Brake Adjustment

Thanks Monte,

I hope to disconnect the MC from Booster tomorrow night.

I will post what I find and whether or not I can make the adjustment without disconnecting the brake lines.

Bill

[Bill L.]

Re: 70 Power Brake Adjustment

It ended up being two things.

In order to get the 1/4" of free play I had to adjust the plunger a tiny bit. Once I made that adjustment I loosened the bracket on the pedal, made a small adjustment and all is good.

Thank you for all the help


Bill