[Jimbro727]

Originally Posted by HWYSTR455

Yeah, I'll take a shot, since there's a couple of grey areas still.

On the rear brakes, adjust them all the way to the drum, with it up on jack stands, and try the pedal with the car running, see if it's the same. Drums, adjusted, drag. If the shoes aren't centered properly on the backing plate, or there's something else out of whack back there, it can have this type of an effect. Take a pick of both sides with the drums off and post them.

You verified the booster push rod and MC plunger distance? What is it? It's supposed to be something like < 3/16s, not something you can eye-ball. You should be using the ears of the MC mounting area as a reference, and that suface on the booster. If there's a question, use a small piece of wax or something on the end of the rod, tighen the MC up, take it off, and see how far it's compacted.

MC bleeding. NO bubbles should come out, and you keep pumping that b*tch until there are NO bubbles. It takes a while, but you do get there. Don't even bother putting the thing on the car if you still see bubbles. You can tap the side with a wrech lightly in between pumps, it helps a little. You don't have to depress the punger all the way, and in fact, think you're not supposed to bottom it out.

MC sizing, yup, you'll probably have a 1 1/8 MC. Those are the type with shallow rod pucks. The 1" manual MCs ONLY come in deep rod puck/hole, which is what some people want, and they still don't make any. Some people have used spacers to use a 1" on a booster. Regardless, you have a 1 1/8, and if it's a 78 T/A, it's the typical GM large/small reservoir type MC. Take a pic, post it.

MC line placement. You say you replaced the prop valve? Which line do the rear brakes plumb to on the master? Usually, the front port on the MC goes to the rear brakes, and the rear ports go to the front brakes. If there's a question if this is correct or not, check the factory service manual. You say you had to 'bend' the MC to prop lines as shipped from Inline to make them work? Sounds like you might have them mixed up. Take a pic and post it.

Prop valve- Does the brake light in the dash come on when you hit the brakes all the way? If so, your prop valve brake bias rod may be all the way to one side, which generally, only effects your rear brakes. Do a search on pro-touring for 'brake bias switch'.

System bleeding- A quick note on this, gravity is ok, but usually on a fresh system, it's hard to get started. In general, however you bleed the system, always start from the furthest wheel from the MC, then the next furthest, etc. Never let the MC go dry, since you'll be re-entering air into the system, and that bubble will have to travel the entire distance to remove.

Booster replacement - You can unbolt and move the MC out of the way enough to where you don't have to take the lines off and re-bleed.


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THANK YOU for your informative response!

I got very excited, because I thought that the lines from my M/C to the combo valve might be wrong, because I have seen many cars with the lines crossed, but I verified in my manual that the rear (closest to the firewall) port on the M/C is for the rear brakes, and the front (closest to the front of the car) port is for the front brakes. The lines from the M/C are two sizes - the thinner one goes from the front port to the left (facing the firewall) port on the combo valve (the one for the front brakes), the thicker one goes from the rear port to the right port on the combo valve (for the rear brakes). Does that sound correct? I can post a picture if that helps.

I have adjusted the rear drums until they drag, but I will take pictures some time today.

I have not verified the booster pushrod distance. Is there a way I can measure this, or should I use wax or something as you described?

I haven't actually been able to get the warning switch connected. It seems as though the rod is too high for the connector to fit, but I hadn't played with it very much. The valve is new from inline tubes.

I've bled the brakes every possible way - traditional (using the pedal), vacuum, gravity, and most recently, pressure.


I do recall there being a change in the feel of the pedal once I replaced the booster. I hadn't thought about it, because I was under the impression that a bad booster would cause a stiff pedal. However, I've read recently that a bad booster can cause a low pedal, too. Is that true? If so, is there any way that I can test the booster?

Thanks again for your reply - I really appreciate the help. I'm getting very frustrated with this problem.