The power brakes on my 79 f150 4x4 do not seem to work as effectively as they used to. They won't lock up at all and it almost feels as if they were not power assist anymore. From what I have read on this sight and from what I have heard it could be the power booster. is there anyway of telling for sure if this is the problem? Thanks Scott

 

Scott: Yes, there is. The most common power booster failure is vacuum leaks caused by deteriorating components. First, check your entire vacuum system and hoses, and make sure you have none leaking. This includes vacuum motors for the automatic transmission modulator, A/C, defrost and heat flappers, etc etc. Make sure you haven't adjusted timing or mixture to compensate for vacuum leaks. If the engine seems to be running OK, then you probably have everything set within specs. Once you have eliminated these potential problems, try the following:
1. Inspect your system. Make sure the hoses are not cracked or leaking air. If so, replace them and see if that solves the problem.
2. Get a vacuum gauge and plug it in as close as possible to the manifold vacuum port for the booster. On the same cluster, if any and if possible. Disconnect the vacuum hose from the booster, and then re-set it on the booster plug just enough to keep it on.
3. With the engine idling, note the vacuum reading. Now, remove the hose from the booster and plug it with your hand, and note if there is a difference in the reading.
4. Do this several times with the vacuum gauge hooked up near and far away from the booster.
If there is a difference in the readings, you have a booster vacuum leak, and need to replace it.
Post back whether or not this solves the problem!

 

Hey John thanks for your help. I don't have a vacum gauge so I called the parts house and they wanted $39.95. The guy asked me what I was doing so I told him. He told me to take the vacum hose off the power booster, plug the hole, and then try the brakes to see if there was any difference. I did this and the brakes were about twenty times worse. Does this mean the power booster is OK or is this an effective test at all?
One other thing is that I adjusted the cable on the parking brake because it was far to loose and the brake was not holding the truck on even the slightest incline. Afterward the cable was tight, the parking brake would still not hold the truck. I am wondering if my whole problem is the rear brakes. I've had a leaking axle seal for some time now (that I can't get rid of) that has coated that area with oil. Maybe some has found it's way to the brake drum. I don't know. Thanks for your help Scott.