What causes the brake pedal to require lots of pressure to push it down? It's like my power brakes have failed. I can still get the truck to stop, but at speed, I have to really stand on the pedal.

Yesterday, I first noticed it. It came for 30mins or so, and then the power came back and the pedal was easy to push down. Then it became difficult again, and the power has not returned.

 

Look to see if any vacuum lines fell off.

If you have good vacuum and no leaks, time for a booster.

 

Vacuum is very low, at idle, I cold only feel the low vacuum with a wet finger. I pulled off hose #5 on the vacuum pump, and it didn't have hardly any vacuum there either.

 

That would be a dead vacuum pump.

 

I was thinking the same thing, Dave. From what I've learned so far, the best thing for me to do is remove the pump, find out what's gone wrong, and goto the cummins shop and get the specific part I need to get my pump going.

Sound like a plan to you and everyone else?

 

You might have lost the bearing on the eccentric that drives the chambers.
If so they can be replaced but you won't know till you pull the housing.
But check the chambers manually first to rule them out.
Jim

 

How do you check the chambers manually? I don't think that is explained in the FSM.

And can I just to the cummins shop in town and pick up the eccentric bearing and all the seals I need to put it back together, or are these special order parts?

 

mine has the same problem but hisses like a snake and when i got my foot on the brake i slowly get power brakes. so i guess that means i need a booster.

 

Yeah, the boosters I've had go bad like to hiss at the pedal. If no hiss, might just need a line or clean-up.