Booster should last longer than that. But you've pretty-much ruled out everything else.

 

Did it turn out to be a bad booster? Having similar problems.

 

Changed out brake booster and brakes are acting the same. its like they intermittently work. Brake peddle is hard and truck slowly stops. Like manual brakes. Gonna hook up vacuum gauge directly to vacuum pump and see if it consistently pulls vacuum. Cant think of anything else.

 

I'm hoping bumping this thread will help spur a solution. I am now having the same issue. Hard pedal and ya gotta stand on it to get it to stop. I plan to test a bunch of things but, don't have a lot of time and it's my daily D.

 

First, make sure you are getting vacuum to the booster. Let it idle, pull the line off, and put your finger on it.
If you feel it sucking, you should be getting some boost. If not... you've either got a vacuum leak or failed vacuum pump.

 

I've had this problem to in my 86 van. I just don't drive it any more but would love to here how you solved it!

 

Checked it this morning. Pulled the vacuum line off the master cylinder drum and am getting suction. However, it doesn't seem all that impressive. It will stick to my finger but, comes off easily. I first noticed this 2 weeks ago when I removed my vac pump to change my fuel pump. It eventually regained power brakes within 20 mins. Been fine ever since. Then, on the way home from a camping trip (while towing), I went to make that last turn off the highway and had to stand on it to slow.

 

Quick update. Drove to work this morn and noticed I had a good 75% power brakes on the first pump. Then it goes hard and difficult to brake. I assume I'm building just enough pressure/vacuum to get one good push.

 

If you change the pump and it works let us know. I have all the same things going on but don't drive it any more to check.

 

Have you checked the belt tension since you removed the pump?

 

^^^^ This. You're on v-belts, right, with a separate belt for the vac pump running off the alternator? Def. check tension of BOTH belts.

 

I will be sure to double check that. I know it was tight after re-install and after an initial double check. My plan is to also start checking suction at every junction from the booster, back to the pump as well. I have some time to work on it tomorrow.

 

The vacuum pump may well be the problem; as they get old, they suck less and less - takes longer and longer to build up pressure in the reservoir(metal can).
It doesn't take that much to turn that pully, so while the belt should be reasonably tight, it's not nearly as bad as the power steering pully.

 

Yeah, I've noticed what a pain in the *** that PS pump can be as far as belt tightening!

I gave new/reman vacuum pumps a quick look online and they're over $100! So much for a "cheap" fix...

 

Well that's a switch, most things tend to suck more as they get older!

Yeah that PS belt can be annoying. Just tore mine up this summer and had to retighten twice.

If it helps any... $100 is nothing compared to not quite stopping in time and effing up your truck or someone's family.