brake problem, broken pushrod or booster, now what?

[sactoC10]

For three weeks I've been trying to fix my "sticking brakes" problem. Fluid, hoses, bleeding, not even a new master cylinder resolved it. So finally last night after repeated attempts at bench bleeding and wheel bleeding unsuccessfully I thought it through further.

Since the master cyclinder is new and working correctly, what could possibly be causing such ANXIETY, STRESS and FRUSTRATION? I think I found out, but I need confirmation.

I have power brakes and thus a booster. The long pushrod that goes through the booster, yup..think mine is broken and getting stuck INSIDE the master cylinder, not allowing my brakes pads and shoes to"back off" and cool off. But when the truck sits overnight, everything slowly migrates back into place, causing all sorts of confusion.

So what is my fix? Pushrod alone? Or whole new booster? If I need an entire new booster, what other chevy makes and years might this one be interchangeable with? I have a 71 350.

Thanks again.

[chevyhouse]

take the pushrod and attach it to the other side of the brake pedal. I'll bet that you put it on the easy side when you reassembled everything, I know cause i did the same thing, had all the same problems you are. if you look really carefully you can see it enter the booster at an ange instead of straight---good luck

[sactoC10]

This needs to be explained further. I didn't do anything but remove the master cyclinder, and when I did the rubber parts of the booster came out with it. Then I attempted to re-assemble everything. And remember, the problem of having "sticking brakes" was happening before the MC was ever even touched.

But I do admit...the problem of having the pedal go all the way to the floor and provide NO pump to the MC is a new one.

So the pushrod (if I am correctly describing the part that inserts into the master cyclinder) has two ends to it, right? the "ROUNDED" end and then the sort of "NOTCHED" end with a rubber O-ring near it. Which end goes into the MC? I was putting the smooth end in there and that seems right, no?

[chevyhouse]

sorry, at 4am i figured you had had the booster out too. I am talking about the other end of the booster-the pushrodthat goes though the firewall. If you hadn't taken that apart maybe this won't help but if that pushrod is on the wrong side of the the brake pedal and not aligned straight with the booster you will have the same problems you are discribing. I spent about three weeks screwing with mine, new booster etcetcetc before we figured it out.

I'm not sure what else it would be though, if you have parts falling out of the booster look there just make sure you put the pushrod back on right when you replace it or you will have the same problems again.

[sactoC10]

Thanks. I am suspecting more and more that it is the booster unit itself. Seems that when these go bad, the problems I am having can be the result. I even read that since it is associated with the vacuum lines in the engine, when the booster goes bad, the engine can rev funny or high.

I thought I was sucking down more gas than necessary, even thought it was idling high, but could not adjust it down. I'll replace the booster tonight and we'll see. The only thing left will be the calipers after this!

[john]

Make sure you have some free pedal when you hook up the booster rod to the brake pedal or your brakes wont release all of the way. I give them 1/8" to 1/4".

[old cool]

My brakes have a little too much play - I think. (power brake conversion) In my search for a solution on the internet, I found the simplest and best troubleshoot techniques came from:
http://www.classicperformance.com/Te...htm#testmaster

Good luck. Look forward to hearing about your results

[old cool]

To all future readers: I realize this is a very old thread - but, the problem seems to be common.
I posted a link above that does not seem to open. If you googl: brake touble shooting guide - classic performance products you'll see some comprehensive stuff.