Hi Fellas, its been a while since I've posted, life has been getting in the way of wrenching! I posed this same question over on ChevyTalk too, so apologies for doubling up. A week ago I finally got to take my 50 Fleetline out for a few laps around the block and noticed the brake pedal was really slow to return to the upright position. So much so, that I had to lean down and pull it back up. Obviously not an ideal situation. After many internet searches one of the more common reasons is a bad booster. But to back up a little, here are the details of my system: Stock rear drums, 1/4" lines to the rear with 10lb residual valve, GM 11" discs up front with 3/16" lines and 2lb residual valve. Under floor GM 1" bore master cylinder with proportioning valve and 7" dual diaphragm booster. There are no fluid leaks ( which I think gives a spongy pedal anyway— not my symptoms) and I've checked the booster both on and off the car. I can use the Mityvac on the booster and it will hold vacuum. I've tried it with both the check valve in place and removed and the results are the same, so I think the booster is OK. I also think the booster pushrod to master cylinder was adjusted correctly by MP Brakes, where most of the components came from. Finally, I checked the pedal ratio (I'm using stock pedals) and the brake pedal is 4.8:1. For power brakes a 4:1 to 5:1 ratio is suggested so I don't think that the ratio is way off, but I can modify it to 4:1. At this stage I'm at a loss as to what else would cause the slow pedal return. Any suggestions are welcome!
When the system was installed did it work properly? Maybe a stronger return spring. Is the pedal rubbing on the floor boards? If the brakes are working properly except for the pedal return put a stronger spring on. Please post what the correction was.
The system performed adequately without being impressive. I put part of it down to the fact that the rears are Huck brakes, but ideally want my brakes to perform better too— especially once I work out this slow pedal return problem. I used to own a 58 chevy with drums on all corners and had a remote booster installed. It would put you through the windshield when you stomped the brake pedal! My pedal moves through the floorboards fine when not attached to the booster and master. I'll try a stronger return spring and see if that helps. The more I read and hear about the smaller 7" boosters, the less impressive they sound. Ultimately it might be better going back to a manual master?
Is that one of those pedals that has several notches for the return spring connector? If so, you could try moving that around to change the angle.
...sounds suspiciously like a sticking bladder in the booster. (not necessarily, but I was testing myself on spelling 'suspiciously'. Nevertheless, I've seen this apparition before...) On a serious note, why the 3/16" vs. 1/4" diameter lines front/rear? Please elaborate?
No multiple notches for the return spring, it's the stock pedal but I could always drill a new hole for the spring. Mike, originally the car had 1/4" lines from the factory and I think it was MP brakes who advise to go 3/16" for discs. So I retained the rear lines and made new front lines. The booster bladder sticking could be a cause. I really don't want to have to buy another booster without knowing for sure though. This once has hardly any miles. Like I said it looks to hold vacuum but on multiple tests it's not consistent. I'm gonna test it again now! Posted using the Full Custom H.A.M.B. App!
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