AC Delco Master Cylinder

[samkost]

Just a follow up on my OE style Master Cylinder swap.
With help from a friend we swapped out the OE master cylinder with the new bench bled master, checked the correct gap for the long piston between the booster and the master ( 1/16”+ gap before pedal activation), and then bled the system starting at the right rear drum, left rear drum, right front disc then the driver side disc.
After a test start up to check for leaks I took it for a test drive only to have the same previous hard pedal condition.
I could not lock up the brakes.
I did need to replace the OE master due to age and a little corrosion but now the focus is on a new faulty (less than 150 miles) POL Power Brake Booster.
I did the two pedal tests and it failed both.
I then ran the engine for a few minutes, turned it off and 30 seconds later unplugged the power booster check valve.
No hissing or escaping air at that point. Booster check valve tested good.
I then got a vacuum gauge to the carburetor vacuum line and found 16 in. Hg of vacuum. I believe and hope that this is good enough vacuum.
So after every said and done, turns out I may have a brand new faulty POL Power Brake booster. I have heard that others have had brand new bad booster issues out of the box.
I will call POL on Tuesday and see what they have to say.
I may just go with my OE original functioning black painted Delco Moraine power booster and forget the pretty Cadmium plated after market booster.
no more bling!
I enjoy working and especially learning about my truck.
Any advice and input would again be appreciated.
Thanks all,

[1972CheyenneSuper]

POL has the worst customer service right up there with Jegs. I had an issue this spring with a break booster/master cylinder setup when I was trying to work the kinks out of a fresh restoration. Called them up and after a few rounds of trying to get ahold of somebody, I get a hold of a Frank or Fred or something along those lines. Very grumpy and annoyed individual. I explained to him that I had bought the setup through a supplier that basically drop shipped their parts. He says no support is available since I hadn't directly bought it from them. I had to reiterate a couple of times that the company you work for obviously has some sort of agreement to distribute the products through various resellers and they're all going to point the finger back at you for support. A couple rounds of that and I finally got through.

I then explained my problem of which I had good pedal feel and the brakes were stopping well, but the pedal would not fully rise without some assistance with your foot from the bottom. The brake pedal arm pivot I had checked numerous times and was free and not binding, the push rod length was correct, the booster check valve was good, the pedal return spring was good(also a second one I tried). Really the only thing I thought it could be at that point was the brake booster. But we didn't get that far in our conversation. He asked me what engine I had in the truck and how much vacuum I was making. I told him I had a cammed LS and vacuum was about 15-16". He said that wasn't enough to make the brakes work. I told him it didn't matter if the engine was running or nut, the pedal would not return. Round and round we went and he was dead set on a vacuum deficiency being the problem and we couldn't even begin to explore other troubleshooting options until I had installed a vacuum pump or similar device to generate more vacuum. I informed him that not another one of my vehicles would never see another POL part on them and we parted ways. He just absolutely would not think outside of the box to offer any suggestions of what was wrong.

A couple hours later of messing around, I finally found that a spacer tube on the fulcrum pivot arm on the booster bracket where it attaches to the booster arm and the brake pedal arm was binding on the firewall bracket. I could have ground it down and probably fixed it, but I removed the entire setup and cleaned up my original brackets, bought a new master cylinder and reman Delco booster and was on my way. I had bought the POL setup originally just because it was a full kit and ready to go, so I thought. Anyways, that was my experience. Give POL a call and see if you have any better luck than myself, and if your bored, check out their Yelp and BBB reviews. I've never reached the point of asking for a manager, but I was very tempted to call back and ask for one, not even for support at that stage but to tell them to watch how their employees conduct business. After looking at the reviews, I knew that wouldn't go anywhere.

[samkost]

Thanks for reply 1972CheyenneSuper.
You bring up an interesting point about linkage clearance/travel.
After reading your post I looked at my Booster firewall clearance and it doesn’t looks right, maybe I’m not getting enough pedal travel?
It looks tight in my photo and there is some fresh paint chips on the firewall.
I do believe that their Booster is bad though.
The tests seem to confirm that.
I need to double check this installation from the restoration mechanics that screwed up several other items.
The Resto shop from hell. did some sub par shoddy work that I have had to correct the last 2 years.
I did purchase directly from POL so we’ll see.
Thanks, Sam