another bleeding the breaks question

[rustynut]

hi all,
got a gmc 2500 4wd
changed the steering pump and cooler a short while ago
to my surprise this pump is not only for steering but for the power breaks as well
anyone know if i need to bleed those breaks after this type of surgery ?
rn

 

[Flatbedford]

First. Do the brakes work OK? If they do, don't mess with them.
I'd say you should not have to bleed. The power assist and the actual brake system are separate systems. Your truck must have what is called "hydro boost brakes ". You only need to bleed the system if you open the brake lines, wheel cylinders, or calipers.
I didn't know that GM trucks used this setup. Is your truck diesel powered?

 

[WayneB]

Flatbedford is correct, hydro-boost and brake hydraulics are separated. As a side note, pulling a vacuum on the power steering reservoir while running will get rid of the whining quickly. They have a hose and a suction cup type adapter that they sell at some parts stores and from some tool dealers that FINALLY became a required tool some five yrs or so ago at the dealerships, boy did that make a PITA job faster and better. Nothing worse than trying to get the foam from forming then running the wheels back and forth twenty five or more times.

 

[Dune]

First. Do the brakes work OK? If they do, don't mess with them.
I'd say you should not have to bleed. The power assist and the actual brake system are separate systems. Your truck must have what is called "hydro boost brakes ". You only need to bleed the system if you open the brake lines, wheel cylinders, or calipers.
I didn't know that GM trucks used this setup. Is your truck diesel powered?

I had hydroboost brakes on a C-30, 6 wheeler.

 

[fbelec]

hydro boost is a real piece of work. try cornering with a heavy load on the back then while turning the wheel as far as it will go to make the corner you put on your brakes and the wheel and the brakes have a war with each other.

 

[Flatbedford]

I had hydroboost brakes on a C-30, 6 wheeler.

That's why I'm curious. I wouldn't expect to see hydroboost on a 3/4 ton. I'm thinking diesel because diesels don't make enough vacuum for power brakes. I know that the Ford light truck diesels have, or maybe had (don't know about the newer ones) a vacuum pump for the power brakes.

 

[struggle]

6.5 Turbo diesel? I had one in 1994. Same system with hydro boost brakes.

 

[rustynut]

just wanting to be sure on that bleed or not
brakes seem a bit light
when the cooler went out i lost brakes and steering at the same time - totally
was messing around in the yard so no problem with traffic.......
never saw that one before
thats a 3/4 ton gmc 4wd w/ 6L gas motor
thanks for the tip on the whining
it seems to have finally stopped
rn