benw1
Well-Known Member
So the last couple months I've been having problems with the power brakes on my '91.5 Cummins. When it is cold out, I have no power assist until the truck warms up. I've been assuming it was the vacuum pump, because everything I read indicated the pump is a common problem. Today I got out the vacuum guage to check it, and found something odd.
1. With the hose disconnected from the booster & plugged the guage reads 30 in. HG.
2. With the hose connected to the booster, the guage reads about 3 in. HG, until I step on the brake pedal, then the guage slowly rises to 15 in. HG.
Is this indicating a leak in the booster? Why would the vacuum reading increase when I step on the brakes? I disconnected and plugged all the other vacuum connections to verify the leak is in the booster.
1. With the hose disconnected from the booster & plugged the guage reads 30 in. HG.
2. With the hose connected to the booster, the guage reads about 3 in. HG, until I step on the brake pedal, then the guage slowly rises to 15 in. HG.
Is this indicating a leak in the booster? Why would the vacuum reading increase when I step on the brakes? I disconnected and plugged all the other vacuum connections to verify the leak is in the booster.
