I replaced the Power Booster on my truck last summer. I got a rebuilt booster unit from NAPA. The new booster didn't fix a problem I was hoping it'd fix. Here's what happens: The power brakes do work pretty good, but if I shut the truck off and leave it for 5 minutes, when I get back in there's no power--it's as if the vacuum is gone from the booster. Once the engine runs for a minute or so it's got power brakes again. I've had this problem for a long time--it was doing this years ago when I got my first rebuilt power booster, (that one didn't fix it either) and then last summer when I got the second one I was REALLY hoping that one would fix the problem. But maybe the booster isn't the problem. What else could cause this problem?

I feel a little stupid about this, but other than losing vacuum, both rebuilt boosters have worked ok. So over the years I've just put off really fixing the problem. But now I've got some time, and I'd like to address the problem. Any ideas?

 

I could be wrong, but I think there is a check valve in the system.....I'd guess somewhere in-line between the vac pump and the booster.

 

There is a check valve and it plugs into the booster and the vacuum line plugs into that check valve. That part came new with the booster.

 

Listening - Similar issue on mine.

 

Yeah! Mine's been doing this for at least 10 years I'm embarrassed to say.

 

'94-'96 had a recall to install the check valve right on the vacuum pump> http://dodgeram.info/tsb/recalls/720.htm

The system still won't hold enough vacuum to apply the brakes more than a couple times if the engine isn't running.
Solution is to run the engine when you brake or to add a vacuum tank.

 

Thanks for that Bill. My gut feeling is that line, or maybe the internal check vavle is the culprit.

 

"if I shut the truck off and leave it for 5 minutes, when I get back in there's no power"

That's normal on all power brake cars and trucks.

 

My original PB booster, from the factory, would hold vacuum at least overnight. It held vacuum like this for many years.