I did a search for my problem and found the answer. Now I have another problem. My parking brake light stays on all the time. I have disconnected the ABS, the light is still on. I disconnected the parking brake switch, the light is still on. I disconnect the vacuum sensor, and the light goes off.

Is my vacuum pump faulty? How do I test to see if it is faulty? The booster has been replaced about a year ago.

Any help will be appreciated.

 

Could easily be a faulty vacuum sensor triggering the light.

 

How do I know for sure? The thing that makes me think it is the vacuum is, the brake pedal doesn't come back all the way up after you press on the brakes.

Thanks, Tony

 

Use a vacuum gauge to check if you have good vacuum. Minimum spec is 8.5" of vacuum, but an intercooled style pump in good shape pulls about 25".

Most likely you just have a vacuum leak somewhere.

 

I did a vacuum test on the pump, it has 28.5 I also did one on the vacuum sensor, same thing 28.5. I did a final test on the cruise, again 28.5

So the vacuum pump is fine. Which brings about two ?'s 1. why wont the brake pedal return to its proper position? 2. Why when I unplug the vacuum sensor does the parking brake light go off? A faulty sensor maybe?

Give me your thoughts on this guys. Thanks, Tony

 

If the park brake pedal does not return all the way that will keep the light on assuming that the p-brake switch is working correctly. Try adjusting the cable. (the adjustment is under the bed in front of the axle LH side)

If the light goes out when you unplug the vacuum switch and you have good vacuum, the switch is probly shorted.

 

Forgive my ignorance, what switch? The parking switch, or the vacuum switch?

I have already adjusted the PB that is when the light began to stay on me.

Thanks for the help, Tony

 

Park break switch.

It's located on the p-break lefer mechanism. Rh side near the top. White plastic and a couple copper pieces on it. 1 wire plugs in to it and it provides the ground when the P-break is engaged.

I'd look more closely at the vacuum switch. Check the continuity through the vacuum switch at 0" it should be closed (o.oo Ohms). Then pull a vacuum on the switch and recheck the continuity. It should be open. (My DVMM says Ol or something like that)

I'd have to guess the vacuum switch is stuck closed and is telling the light to stay on.

 

Yes your probably right. I have disconnected the PB switch and the light still stays on. So I don't think it is the PB. Thanks again, Tony

 

Get yourself a dash-mounted vacuum gauge; it will be a handy trouble-shooter many times in the future.

I have two, one for truck vacuum and the other for trailer vacuum.

The pedal that is not coming back up--are you meaning the park-brake pedal, or the service-brake pedal ??

 

You were able to pull 28.5" or the pump was pulling 28.5"? What's the vacuum reading at the pump outlet with the engine running?

It sounds like you have a bad booster, replace it and the master at the same time. The reason for this is that 9 times out of 10, the booster failed because the master let brake fluid seep into it.

 

The service brake pedal. Once you press on it to stop the truck it only comes partially back up, and then it keeps the electric brakes engaged.

 

Not sure I understand. With the engine running each time I checked different locations first the pumps main line. 2. the vacuum sensor. 3. the cruise. All three locations were pulling 28.5".

I did replace the booster, and then later the master cylinder so maybe I should do both again at the same time.

Thanks again, Tony

 

OK, since you listed 3 locations I thought you were using a hand pump to check for leaks.

The vacuum pump is working great, replace the vacuum sensor.

 

Take your hand and pull up on the brake-pedal, then test the vacuum-sensor.

It is possible that the brake-pedal being down that it is giving a false reading.

Also, examine the bushings on the pedal assembly for possible binding.

If all that is okay, then I would suspect that something wrong with the booster is hanging up the pedal.