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aray327
05-29-2008, 07:25 AM
I just installed a new power booster to my brake setup this weekend. The booster is new from Classic Industries. My brakes are all new from CCP including the master, which I was told I could run manual until I was ready to add the booster.

I measured the adjusting rod coming from the booster to the master and made sure the length was right. After getting it installed and driving the car the brakes will maintain pressure causing the brakes to lock. It appears to be caused by the booster as if it builds pressure and applies it to the master. After the car sits overnight there is no line pressure but if you drive a few blocks applying the brakes it will build and cause the brakes to stay applied. I did not have any issues when using the master as a manual brake systems (except stiff peddle and more brake effort).

Not sure if the booster could be bad or if there is something I am not considering or overlooked somehow. Suggestions are welcomed.

Mike Holleman
05-29-2008, 08:48 AM
Sounds like you may be preloading the master. When you mount the master to the booster, does it slide right up to the booster or are you having to pull it in the last little bit with the nuts?
Mike

6'9"Witha69
05-29-2008, 09:23 AM
Between the intermediate rod length and ensuring that the pedal rod is adjusted properly to not preload the system.

aray327
05-29-2008, 03:50 PM
I did have to adjust the rod after the first test fit. However I measured as much as I cound and made the adjustment. Remember the brakes initially are not applied and the wheels turn freely. Only after driving the car does the master apply pressure and lock up the brakes. If the booster was preloading the master the wheels would have brakes applied at all times not just after being driven; I believe...

amx2334
05-29-2008, 04:08 PM
I think it's the rod from the pedal to the booster. If too long the valve in the booster won't work properly.
When the brakes are locked can you disconnect the vacuum line and see if it returns to normal?
I copied this from one of the instruction manuals:


7. Using the supplied hardware attach the push rods to the brake pedal and booster. Adjust the push rod lengths so that the brake pedal is as high as possible without preloading the brakes. Tighten all of the hardware on the bush rods.
Warning: Preloading the master cylinder will cause the brakes to drag, and lock up.
8. Configure the master cylinder push rod bore to match the booster pushrod. There is a special tool (Part Number CP2003) available to aid in adjusting the pushrod. A correctly adjusted push rod will not preload the master cylinder.
Warning: Preloading the master cylinder will cause the brakes to drag, and lock up.

aray327
05-29-2008, 05:16 PM
I thank you guys for your suggestions. I will again check the rod length to the master and the rod length to the pedal. However, the rod from the pedal to the booster doesn't have any pressure on it. You can adjust the height of the pedal but until you apply your foot it doesn't put any pressure on the booster. I connected that rod last to make sure the peddle wouldn't be too high. Also the check valve would keep presure in the booster so disconnecting it wouldn't do anything after the pressure is applied (I thought about that last night). I will play with it again tonight if I can.

Any other ideas are welcomed.

Mike Holleman
05-29-2008, 06:31 PM
If the master is preloaded the master is unable to fully close. This causes residual pressure to remain in the master when the brake has been applied. Several applications of the brake and you will have lock up. When it sits for awhile the pressure will bleed off. This sounds like what you are experiencing.
Mike

6'9"Witha69
05-30-2008, 08:16 AM
Do you hav ethe return spring on the pedal? If shot or missing the simple weight of the pedal, if not perfectly vertical, can make some pressure in the system.

aray327
05-30-2008, 01:24 PM
The return spring..... that sounds like something that would make some since. I took the booster out last night, i figured I could get a better look at everything out of the car. I did see a spring hanging under the dash that seem to have no purpose. However I didn't see any place it would attach to the peddle. I will look at the spring and where it could attach this evening.

I'm planning to measure the rod again and maybe try to shim the master to the booster with a washer if it looks like I need extra distance. My master has a shallow hole for the rod and I have shortened the rod down as much as possible. My rod only extends about 1/2" or less from the face of the opening in the booster so I don't have any adjustment left.

There is one other bump in the travel of the brake peddle that I wanted to look into as well. When I apply the brakes about 1/2" the peddle bumps as though it was cought on something and then continues to travel until fully depressed. I couldn't see what could cause it in the car so maybe out of the car I will be able to tell.