Brake issue

On Mrs. Cusser's 1994 Suburban, the booster started hissing like a snake when the pedal was pushed, and the brake did not work as well. That was a pain in the buttski to R&R, required re-bleeding the brake system, and I had to buy a 15mm deep socket that was 3/8 drive, and I ditched the GM locknuts that were on too-long booster studs and took like an hour to loosen (decided not to cut the studs shorter on the new booster, but to instead use regular nuts and lockwashers from Ace Hardware for $1).

Anyway, I can't remember if the brake booster on my '88 B2200 hissed or not, but I did check to see if it held vacuum withmy hand vacuum pump, and it did not. Anyway, I was able to just move the unbolted master cylinder forward without disconnecting any fluid lines, so I was able to R&R this one readily, without the need to bleed the brake system. I did have to adjust the booster pushrod length to I'd have a teeny amount of freeplay to the recess in the master cylinder.

Hint 1: measure the length of the existing booster's pushrod, and match the length of the new one to that.

Hint 2: the rubber vacuum line that connects to the booster has a check valve in it, and arrow for direction, don't substitute with plain hose !!!

Moderators: see, Merciless posted under Engine General, so I'm not the only one confused by the lack of appropriate categories.

I check out the brake booster as well, see what I can figure out.

I posted here simply because the main "Repair Tech" forum only had 9 topics, whereas this one has a large amount on a variety of issues.

Yes, I must say, the categories aren't exactly intuitive, especially since these engines were so similar many topics apply to multiple engines, but is an engine question (e.g., 2.0 and 2.2).

First of all, where exactly is this check valve, because all I'm seeing is a plain black hose? I tried checking all hoses for leaks, although that check valve would probably give the same symptoms as a bad booster.

Now for more symptoms. When the truck is off, I can pump the brake and it gets hard within 3-4 pumps. When the truck is on, I cam pump the brake and it gets hard within 5-6 pumps. When pumping it, I can hold it (and the pedal is noticeably higher than during its "current" state) and it won't leak down. However, if I wait a minute and slowly pump the brake a couple of times, it loses the "build up" and goes back.

Bad booster? Missing check valve? Truck just doesn't wanna stop?

I "think" that after you shut off the engine that there "should" be sufficient vacuum for a stop. So I think I'd run the engine, then shut it off, then see what the brake pedal feels like.

In general, you should be able to stop the truck using the brakes with the power booster disconencted, it just will take more foot pressure. My old VWs do NOT have power brakes, and they stop. It just should be better and easier with the power brakes.

Are you saying that you essentially cannot stop the truck at all? That may be more than just a power brake issue. Did you try with the jacking up and seeing which wheels are held stationary when the brake is applied?

Brakes are dangerous to you and to others, maybe consider taking to a mechanic.

No no no, the truck stops. As I said in the beginning, "It works, works well, but I definitely ain't saving any deer with the brakes."

It's like I'm taking just a little longer to stop than what I feel I should be.

I'll check out the initial vacuum hose. Given the history of my truck, it's possible the POs replaced the hose without knowing the check valve resided in it.

Come to think of it, this was my symptom before I replaced my B2200's booster. I got a lifetime warranty replacement from O'Reillys. It helped mine. " target="_blank

It was the leaky booster on our 1994 Suburban that hissed like a snake when someone pressed on it.

Quick question, Cusser. If that turns out to be the issue, where, do I get another? I've looked all over Rock Auto and others, no dice. I hope you know of a place to order these.

never mind. found some at oreilly

Well, the check valve is there and working. Next I'll jack up the truck and check each tire for proper braking. I'm fairly certain both backs are okay because I had my wife hit the brake pedal to ensure I was adjusted correctly. I guess it's possible I have a bad/plugged caliper.

Yes, check that first. But maybe your booster pushrod is adjusted too short, causing you not to be pressing the master cylinder piston down far enough. That pushrod length (or brake pushrod length if without power brakes) needs to be checked and/or adjusted every time a different master cylinder is swapped in, the master cylinder recesses/castings have slightly different depths. Too long a pushrod adjustment will cause brakes to lock up, or lock upo as they get warm after a few minutes of driving. Too short means the master cylinder piston doesn't get pushed in far enough. I measure the depth of the existing MC and the new, and adjust that pushrod length accordingly. I also needed to adjust that when I did buy a new power booster. So don't discount that.

But it might turn out to be the power booster.