hpoe somebody can help,i have a 1986 3/4 ton light duty.when i drive the truck i can here a vacum leak, when i apply the brakes the leak stops.i have replaced the hose on the brake booster and checked everything i can think of.i,m not sure if the booster is bad or not because i still have good brakes any ideas?

 

Don't know if you have figured out your problem, however on my 85 F250 6.9L I had to replace the boost package and then the vacuum pump. That fixed the problem. I believe the real problem was the boost package, but by fixing that problem it put a lot more stress on the vacuum pump.

 

I recently had my front brakes rebuilt on my 85 F250 6.9L XLT replacing the booster package, vacuum pump, rotors and pads. The shop I had the work done at said that the OEM calipers were in good condition and did not require replacing. The truck has 104K originial miles. Three days after the work was completed I was about 160 miles into a 180 mile trip (which I make about every 10 days). The right front start to make a low frequency rumble and eventually started to pull to the right. About 8-10 miles later I pulled off on an offramp and went around to the right front only to discover the wheel assembly in flames. Fortunately the fire didn't spread and went out in a few minutes (lesson learned .. where was my fire extinguisher!). There was so much heat produced (freeway speeds on a dragging brake) that the bearings and caliper melted into a mass of unrecognizable metal. The spindle bent with the weight of the truck resting on it while I was waiting for the tow truck. I was pretty fortunate that the wheel didn't come off the truck. From the time the noise started and I realized I had a problem it was no more than 5 mins or so. I guess a lesson learned from this is that with a truck that is 20 years old it might not be a bad idea to replace the calipers when doing a brake job. Probably just as important, if you sense something is wrong with your brakes, don't waste any time ..pull over and check it out! Fortunately for me the shop who did the work is paying the bills for the repair and car rental.