LanceD

lately my brake light has been coming on while sitting at an intersection with my foot on the brake. the petal doesn't move at all, but if I push it once, let off and then push it again, the truck won't stop and I have to floor the petal to get the brakes to work. when I rev the engine or start driving, the light turns off and brakes work fine next time, unless I push them a few times. is my booster going bad or my pump?

Fishinghaoliboy

Could be either or neither but a few simple tests should tell you. The brake booster is fed from the back of the pump up by the injection pump. I got a few pieces of hose from NAPA about a foot of each size and I had a vacum pump with a vacum gauge on it and I also bought a couple of those tees that will fit different sizes and then started testing for vacum. The line from the booster forward has a tee in it (on a 96) down under the battery. This line feeds all of the vacum accessories in your dash. Disconnect that line and hook a vacum gauge to it and start your truck and see if it builds vacum and then shut the truck off and see if it holds vacum. You should get 18 inches or more. If it makes the vacum and holds it you have eliminated the pump and the booster and if you drive it like this your brakes should be back to normal. Then proceed to follow the line you disconnected with your tester hand vacum pump and test each one of those small lines that go into the dash and see which has a leak in it. The hand vacum pump can build vacum in the small lines very easily. My friends truck had a leak right at the back of the motor where a vacum line takes off and goes down to the 4wd shift controls at that transmission. There is an odd little connection there and it just bounces around on the hanger and the line had a crack in it. It took me about 15 minutes to find and he had had the brakes replaced and the vacum booster replaced twice in a 2 week period and they didn't seem to be able to find the problem. Hope this helps and vacuum doesn't look right I think I left out the u.

Denny

LanceD

thanks for your help, I narrowed it down to my vacuum line going into the top of the transfer case came off

Fishinghaoliboy

Glad that helped you Lance. My buddy was pulling his hair out after going to 2 brake shops and they couldn't figure his out.

Denny