wsmm

Member
I have a brake question on my 1990 Chevy K1500. It's my plow truck so this is some what of a tool question. Lately I've started having problems with my brakes. I'm not loosing any brake fluid, so that should rule out leak. When I start out I have good pedal pressure and height. A little push on the pedal and the brakes seems to engage. As I plow, usually about an hour or so, with a lot of starting and stopping, due to the way my driveway is, I seem to loose pedal pressure as the pedal does seem to apply the brakes until close to the floor. I can always stop though. I'm at a loss as to there the problem is. Might add the truck does have power brakes.
 
Might be a caliper not releasing properly and boiling the fluid. My 93 F150 started doing that a few months ago. It kept getting worse so I bled the brakes one at a time until I found it. Left front had a tiny bubble. Worked perfectly after that until a week ago and I noticed a creep. As soon as the weather gets better I'll have to change the calipers.
 
Check all four brakes,adjust the rears. You may be losing the booster,the way to check it is easy. When you notice the brake fade shut the truck off,pump the brake pedal a couple of times,hold the pedal down and start the truck. The brake pedal should drop,if it doesn't go down, the booster is bad.
 
Most likely it's the master cylinder bypassing. Try very lightly applying the brake. It doesn't have to be moving. If you ever so slowly push the pedal, usually a bypassing master cylinder will let the pedal go to the floor.

Another thing to check is the front wheel bearings. If there is a loose bearing, the wobbling wheel will cause the rotor to push the piston back into the caliper. Then when you hit the brakes again the piston has to come out to meet the rotor.

And if it has rear drums, a stuck adjuster will cause low pedal.
 
Sticking caliper and your hand on the wheel (close to it) might be able to find it fast enough once it acts up again. Heat is very educational.
Could also be a brake hose collapsing internally. Seen that once or twice.
Once you find it, you might consider replacing both unless you desire to open it again.
 
Never heard of such, but my 2009 Honda Element owner's manual says to replace the brake fluid ever so often...forget the time line in the maint chart. They said that the brakes get spongy. Seems the vent in the BF reservoir allows access for it. I had soft brakes occur on other vehicles before and tried a lot of things to firm them up but replacing the fluid may have solved the problem...just didn't think about it...just "bled" them and figured that was all you had to do.

The heat generated in your frequent applying could be causing the air to expand rapidly causing the problem. For $5 worth of fluid and an hours's work, It wouldn't hurt anything to try it...who knows it might solve the problem.
 

This is somewhat of the way I bypass the dump valve.

https://www.gmt400.com/threads/1990-c1500-abs-rwal-removal.11427/

Its been awhile I don't remember the particulars its easy to do and will improve braking performance if its an ABS issue... I don't buy any fittings I can make my own brake lines so I cut the fittings off the old and add to the new...

Fords of the same set up get by passed also : ) But don't tell anyone cash only...
 

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