Brake booster

mbalbritton

mbalbritton

#@$%!
Joined
Mar 22, 2005
Location
Lakeland, FL
After replacing the valve stem seals on my 304, I reinstalled the Brake Booster and MC. I still need to bleed my brakes a little better, but now I have virtually no pedal and the engine wants to stall when I push the brake pedal. Yes I hooked the vacuum hose back up. It idles and runs fine. But touch that brake pedal and the engine starts stumbling and stalls. Tells me vacuum leak. I did notice the rubber seals/grommets on the brake booster pushrods going into the MC were far from pristine. Could I have disturbed what was left of a seal on these? Here's a picture from Parts Dude4x4 of the booster. Part 3 and the little rubber seal on the end of part 2 are the ones I'm wondering about. Any thoughts on sudden stalling issues after removing and reinstalling brake booster & MC?
ImageUploadedByTapatalk1448847338.722639.jpg
 
I'm running into the same issue on my Toyota pickup. Have to double pump for any pedal pressure and the motor will stumble.... I'd love to know where to troubleshoot.
 
I'm of no help here but if someone educated in boosters will reply, I'm all ears. I had an issue with a 99 Tj with 6.0 LS in it almost the exact opposite of what you guys are having. I had a terribly stiff pedal and when I'd stand on the brakes the engine rpm would rise ever so slightly.
:confused:
 
You most likely have a tear in the booster diaphragm. when you press the brakes it stretches the rubber diaphragm and opens the tear/split allowing a large vacuum leak.
 
Btw, I stopped by the parts store this weekend and asked the kid behind the counter to pull up the MC and Booster for my Jeep. He pointed at the two bumps on the lid of the MC and asked "What are those for?" Then pointed at something else (I forget what) and asked what it was.

Both very basic things. I said thanks and left.
 
If it is only dying/stalling when you have the pedal depressed, then regardless of whether it's a tear or not, the problem is internal to the booster.

If the booster has gotten oil in it or if the master cylinder has ever leaked out the rear seal into the booster it will soften/swell the diaphragm and cause problems. Also, with age, like any other rubber piece it can dry rot/split and cause leaks as well. Either way, it is a booster issue.

The soft pedal is just air in the system or a master cylinder problem. Booster issues will not give a soft pedal, if anything it will be harder than a proper booster with proper vacuum supply.
 
$25 in speed bleeders, a bottle of brake fluid and 30 mins to swap bleeder screws and bleed the system. All is back to normal. Good pedal is not surprising, but the engine stall is gone too. That one I found weird.
 
Could have a fissure in the diaphragm that only opens up when stretched by fully depressing the pedal (for now.) It will likely get worse if that's the case.
 
Maybe. And I don't begin to say I know the full function of a booster. But I could barely touch the pedal before and the engine would start to stumble. That's what makes it weird to me.

I don't know. All I do know is it's working now. ...for now
 
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