Power brakes becoming un-powered???

Hi all, My truck is doing something strange I haven't experienced before. Its a '95

1500 2wd. The brakes work fine on the first pump, but each consecutive pump has less and less power assist, until on the fourth or fifth pump it has fully manual brakes. Not exactly a fun or safe situation. After driving another 30 or 60 seconds the power brakes will be recharged for a pump or two.

My guess is a leaky power-brake vacuum diaphram? Does that sound right, or might it be something else?

Thanks a lot, Brian.

Reply to
Brian
Loading thread data ...

What engine do you have? Check your vacuum source? I have seen the older 350's with throttle body that the vacuum pipe gets clogged with carbon and also where the fitting screws into the manifold. If you have the pipe that comes out of the manifold towards the front and then loops around and runs along the left side valve coverand then points up with a small canister before connecting to the booster, take the pipe out and try to blow thru it. If you can't then either try to get a new one or just take it and put the whole pipe in a small fire (like a charcoal grill or fire place) and let it burn out the carbon inside the pipe. Leave the pipe until the ashes are cool and the try to blow out the carbon and then repaint the pipe when done.

Reply to
WBucha

I agree. You need to check your vacuum lines. Chances are it is partially stopped up somewhere and it just takes a little time to rebuild pressure.

Reply to
Tony Thomas

On the side of your power booster you will see a hose going from the booster to the intake manifold. Along the hose you will see a plastic canister about an inch and half in diameter and two inches long. This is a vacuum filter, when it clogs it reduces the amount of vacuum "flow" to the booster and causes the brakes to act exactly the same as you are describing. It is a $10 part from any parts store and will take 5 min to change. See if you have one of these filters if so change it and see how you make out.

good luck, mark

Reply to
rock_doctor

Thanks for the tips guys. I checked the tube, filter, and check valve, and they all seemed to flow fine. I put a vacuum on the booster (sucked on the tube, yuck) and I would get a little flow out of the booster. I'm thinking that it should be sealed tight. So, I'm gonna go get a booster and try it out. Aftermarket I'm afraid, for $110, the dealer wants $436! What a jip! Thanks guys, I'll let you know how it goes. Brian.

Reply to
Brian

If the booster is leaking then you should be able to let the truck sit for about 5 minutes after shutting it off and then pressing the brake pedal see if there is any assist. If there is enough for one or two presses of the pedal it's probably not leaking.

Brian

Reply to
el Diablo

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.