Stalling when braking

[KelseyM]

So I noticed that when I apply the brakes the engine rpms drop and I can hear the brake servo sucking in the exhaust. If I dont wait for the truck to warm up she just stalls, but once at around operating temp she just drops the rpms and is normally fine, no stalling. I have to pump the brake twice in order for the pedal to not go to the floor. I bled the system there is no air in the lines.

Last night I was driving home, coming down a hill when the pedal just let go, and the truck stalled. I had to keep the revs up for about 2 miles, noticeably down on power to get home so she wouldnt stall.

I just started the truck up and noticed that the idle was rough and the charge light was on.

I was thinking maybe vacuum leak but am not sure, any ideas? Thanks.

[martindktm]

Looks like the bosster is dead. Diaphragm inside is probably broken.

[Terrys]

Looks like the bosster is dead. Diaphragm inside is probably broken.
And you need to adjust your shoes. Boosters can be rebuilt. Chances are it's sucking in air on the pedal input shaft side, so the rubber boot is probably all cracked too.

[KelseyM]

it stopped raining, I am going to pull it out and see whats up,

Terrys: I just replaced all the brake shoes, drums springs about a month and a half ago, about how often do they need adjusting?

[KelseyM]

So I pulled out the booster, how do I check to see if it is bad? I am assuming that I need to bend all of the pinch points and remove the two cases from one another but wanted to post this before I did anything incase I am wrong

[Terrys]

So I pulled out the booster, how do I check to see if it is bad? I am assuming that I need to bend all of the pinch points and remove the two cases from one another but wanted to post this before I did anything incase I am wrong
Kelsey, before you do anything to the booster, pinch off the hose, start it up and see if the stumble has gone, Yes, right? OK now, hook the hose back up, start the engine, push in the booster actuator rod (the one with the hole for the pin) slowly, noting how far it's gone in before the stumble. When it stumbles, push it all the way in and see iff it smooths out. It it does, it's likely rust pitting on the barrel of the housing, and when the rubber runs over it, it looses it's seal. someone once told me that's when you throw it away and buy a new one. I didn't, I opened it up (sure enough, heavily pitted) cleaned it well, took some JB weld and smeared the whole surface, then sanded it back smooth, and it went fine another 5 years. If the stumble stays for the whole length of the booster stroke, it's probably the diaphragm ring.

[KelseyM]

Terry, thanks for your imput, I just did what you told me but unfortunately it stumbles the whole way through, so I guess its the ring. Sounds like I am going to be replacing the unit! Thanks again, you have been a great help.

[Terrys]

Re the double pedal: When you install new brake componants, you almost always have to readjust after the first few miles, but if you're having to double pump, it's because the first pump moved the shoes up, towards the drum, but the amount of fluid moved wasn't sufficient to bring them up to the drum. The gap is too great.

On the booster; there is a rebuild kit available, or, at least RN had one listed, though I'm finding alot of 'Oh, that's no longer available' from even current published info.

[KelseyM]

Ok, I am going to call RN today and see if they have it in stock and I will adjust all the brakes again once I install the servo.