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K3500 brake pedal adjustment

mikpits

By mikpits
in Ask A GM Technician

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mikpits New Member

mikpits

Posted
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I've got a 91 K3500 dually with a 454. The hydroboost was leaking so I got a replacement - making sure the old and new ones were identical. I put the new one in and now my brake pedal is 5 to 6 inches higher than it was.

 

Originally, I put everything back in - even the switch on the front side - towards driver - of the brake pedal arm. When I would turn on the vehicle the hydroboost would kick in and after a few times pushing on the brakes the pressure in the front brakes would build up to where the front wheels were basically locked. I resolved it by pulling out the switch on the front side of the brake pedal arm and allowed the brake pedal to come out another 5 inches or so. SOlved the problem, but now my brake pedal is dangerously far away from the acellerator. Also whatever that switch is supposed to do it's not doing it because it's just dangling there.

 

I'm supposing in the wiring in there somewhere there's supposed to be a pressure relief switch that tells the hydroboost to stop pumping or something. Is that what the switch is supposed to do and just not doing it?

 

I even removed the hydro boost to see if the rod from the hydro boost to the brake master cylinder was too long for the new hydroboost unit, but the new and old hydroboosts have the same distance from the plunger on the inside.

 

ANy thoughts?

 

Thanks for the help.

 

Mike

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
I put the new one in and now my brake pedal is 5 to 6 inches higher than it was.

 

Is that an exaggeration? I don't see how you could get it that high even with everything was disconnected and you pulled the pedal as high as it could go. Been a while since I've seen a '91 though.

mikpits New Member

mikpits

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  • Author
Posted
It definately sounds like something when awry in the reinstallation procedure, as I don't know how you'd get it to move 5-6 inches from where it was before.

 

 

 

 

 

Thanks for the responses - I used the same rod. The new hydroboost doesn't have a new rod so I had to use the same rod.

 

Oddly enough, I could get the brakes back to where they should be if I bled them. But then after driving around for 15 minutes and hitting the brakes - or even just pumping them the pedal would keep coming out furhter and further.

It's quite a ways from where it used to be.

 

When I step on it to stop it only travels the normal 2 - 3 inches I'd guess until it stops and the brakes are fully engaged. It works ok, it's just that it's so much further out. What regulates the amount of power steering fluid in the hydroboost? Or what regulates the amount of Brake fluid pumping intot the brakes. Like I said, I could bleed the brakes - well, what I did I put my son in the truck and had him push on the brakes and I opened the bleeder valve and got some brake fluid out until the brake pedal went to the floor. then I closed the valve. The brake pedal was back where it shoudl be. Then I pump pump pump, or drive it around for 15 minutes and every time I hit the brakes the pedal advances a little bit until eventually it's way out.

 

There's some valve or swithch that's not invoking to tell either the Brakes to stop taking fluid in the system or the hydro boost to stop taking so much steering fluid.

 

Thanks for any thoughts- I'm stumped.

 

Mike

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