I have an problem that comes and goes at odd times on my 93. Sometimes when I first start the truck the brake pedal is hard and the brakes don't work very well. Other times it is fine. This also happens once in a while when driving. Most of the time they are fine, the problem is you never know when they will act up and it can be very difficult to stop. I've noticed that the passenger side will slide on lose dirt also. I never get a brake light to indicate that I have low vacume. How low does it have to get before it will make the light come on? I know that the front pads need to be changed and I have a slow leak in the wheel cylinder on the right rear brake. Could these two things combined cause my problem?

 

The hard pedal is going to be a vacuum problem. I dont think the brake light comes on for vacuum at least it doesn't on my 86.
The leaky wheel cylinder needs to be fixed asap as it will only get worse, and it will cause that brake to grab.
Front pads are cheap and easy if you don't run them long enough to ruin your rotors.

 

Starmilt, his is `93 so should have the low vacuum sensor connected to the red light. Although that does not mean that it is working.
I don`t know at what vacuum the red light comes on but vacuum should be around 18" if pump is OK. It might be worth checking the vacuum to see how healthy the pump is.
However the intermittant nature of the problem may point to a bad booster. But eliminate the pump first. Also make sure the vacuum pipe is good.

 

Actually the brake light comes on, even on the 86 model trucks.
The low vacuum switch may not turn the light on anymore, mine seems to stick sometimes, but it does turn on the brake light eventually.

Three things turn the samer light on, the valve on the proportioning valve that senses a broken brake line front or rear, the parking brake and low vacuum.

Another indication is the heater defaults to defrost when the vacuum gets low.

 

Thanks for the ideas guys. The heater works fine in all settings. This weekend I will put a vac guage on the pump and see what I got. Where is the best place to plumb it to get a good reading? My guess is going to be that the pump is fine and the proportioning valve is starting to go bad. The other brake issues are on my short list.

 

Plumb guage onto the vacuum manifold...... and no it will not be the proportioning valve.

Vacuum may not be low enough to deflect the heater to windshield, BUT it may be low enough or NOT recover fast enough to operate brakes correctly.

Sent you an email.....