K1500 Scary Brakes

[rokbrnc]

Hey All...  I have a '96 K1500 and just recently, while pulling up to a stoplight, it felt like I had lost my vacuum and the brake pedal went almost all the way to the floor.  The brakes are a little mushy when coming down from speed, but when slow-going it feel like I have no stoppinhg power at all?  Any ideas what might be causing this??  Booster failure, vacuum leak, manifold pressure????  Thanks....

Dean

[BDBWTE]

A) are you new to Chevy truck brakes??? the older ones have the classic mushy pedal

B) if not I'm guessing you've checked for leaks and duh the DOT 3 brake fluid in the reservoir..

C) the brake booster might be on her way out...

D) you checked for leaks between the brake booster and the master cyclinder?

E) Bleed brakes

F) There isn't any pinches in the Steel or braided lines?

G) After that I don't know..

[rokbrnc]

Thanks...BDBWTE

 

I have gone through all the normal stuff, and I would think that if something was wearing out that it would have happened gradually.  This was extremely sudden....one minute I had brakes and everything was working fine, and the next minute I didn't...  i was just pulling out of a parking lot, and up to a stoplight...  

 

Dean

[Shaners]

I don't have an answer for you, other than to check the obvious.

 

The only thing I have to say is that a brake issue is a serious issue (as you obviously know), and that if it continues, and if you can't find the problem, then you should take it to an expert!!!  

 

I have had a brake system "power bled" after I couldn't get the air out conventionally to cure a mushy peddle and brake fade before...  This was after I had gotten some air in the system somehow, and couldn't pump it out with the peddle.

 

Will your brake peddle pump up at all?  Or is it just consistantly mushy?

[HeyJoe]

I had a similar experience recently with my '99 Silverado, but I believe it was a stopping situation that triggered the anti-lock brakes.  There's a stop sign near my house that is just past the crest of a hill on the downhill side, and the small crest itself is on a road that slopes down sharply (picture one of those wavy carnival sliding board rides, where you sit on a burlap sack).  The result is that the road tends to throw the truck up into the air right before the stop sign.  If I come down the hill fast, when I go over this crest and hit the brakes for the stop sign the pedal will vibrate as it smushes down to the floor as the truck stops.  It will happen more easily if I am going fast or have the rear tire pressure up pretty high.

 

I haven't had a chance yet to really do a deliberate test of the anti-lock brakes (would prefer to do that on ice or snow rather than dry pavement), but I only have this experience on this one stretch of road, so I haven't been concerned, particularly since it is influenced by tire pressure.

 

I'm due for service now anyway, so I'll have them look at it.  Better safe than sorry.

 

-- Joe

[JuanB]

 Hi Dean:

 You might look at this. Some trucks with average wear and a few miles/years on them have "Mushy Pedal Brakes".

There has been alot of talk on many boards of this problem. Some times new brakes, rotors and having the brakes bled won't fix the problem. This is when I look at the Brake Hoses. They have rubber centers that will expand(Balloon out effect) with time/miles/hard driving. Try replacing the brake lines with a Stainless steel line kit. I'm having the same problem and am waiting for the parts right now. Hope this helps and Good Luck...JohnB

[bobc]

Joe wrote exactly what I was gonna say.   I've had my brake pedal damned near hit the floor coming to a stop where the pavement was rough causing the rear end to get light.  Pedal didn't pulsate like you would expect with ABS, just dropped out from under my foot.  Definately disconcerting feeling.  But I stopped AOK, so..  :thumb:

 

My friend had a 99 suburban with the prev body style.  His brakes were always wierd and damned near hit the floor under normal stopping.  Prev generation GM trucks definately are notorious for strange overly mushy brakes.

 

Check the hoses and all that if it still feels funny.  Also if you stand on the brakes at a stoplight the pedal should sit solid, not leak down.  If it does and you can lift, reapply and the pedal is solid again the master cylinder is headin south.

 

haha I just remembered that the previous owner of my old ford truck thought the pedal was too low so he heated it and bent if upwards for more travel..  Probably not recommended.  

 

later!

bobc