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Brake upgrade question

BlazerEMT89

BlazerEMT89

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I just swapped 3/4 ton axles into my 89 k5. I am now having a problem with my brakes being super soft. The brakes are also catching about 2in from the floor boards.
I have searched for a while so I can't seem to find a straight answer.

So my question is what are upgrades I can do to make my brakes work better? Can I put in the 3/4 ton master cylinder and brak booster? WOuld that be a direct swap?
 
I dont know if this helps or not, But I have a 1/2 ton Suburban, I swapped in a 14 bolt and a Dana 60 and didn't change anything. Have you blead the brakes a few times. Maybe there is a air bubble in there somewhere. How about your softlines, Do you have hardline going to the T bracket and soft lines from there? Or do you have a 8" softline at the caliper and hard line from there?
 
Soft pedal generally means either air in the lines or a bad master.

Bleed the system again. Repeatedly. :D

-- A
 
I have bleed the brakes several times myself and went so far as taking it to a shop for them to bleed them. Hasn't changed anything.
 
When I swapped my rear axle to a 14bff several months ago on my 89 I also had very similar issues with the brake pedal. A buddy and I bled the brakes for hours trying to get all the air out and improve brake pedal feel and performance. Ultimately we borrowed a brake bleeding "tool" from another buddy. Can't remember the name brand or catchy little tool name, like hydro bleed or something.

This consisted of a reservoir, filled with brake fluid, attached to the master, which you pumped up (an internal hand pump, in the center of the reservoir canister)the entire brake system and pushed all the air out to the individual bleeder valves at each corner. I then went around to each corner and bled them one by one. Found a bunch of air in the system. Surprised to find air in the fronts as I hadn't even touched them or the brakes while doing the rear axle.

Very nice and handy deal. You can bleed brakes by your self and not pump the brakes, or worry about the master running low. The pump keeps pressure ( about 10 psi) in the system at all times as it is closed system. The reservior is pushing brake fluid in the master as you bleed at the corners.


I don't know if these trucks are notorious for air in the system, but I have never chased air in a brake system in a vehicle in nearly 20 years of messing with cars / trucks.

P.S. Seen newer systems like that I used now but they push the air up to the master. It was Stacey David either on an old Trucks episode or his new one on Speed Channel.:dunno:
 
I had no issues when I swapped axles in my rig. Are you running drums or disc on the rear?
 
With the engine off and no boost, the pedal should push down a certain distance and then stop.
You should not be able to push it farther. If it does not stop solid, but feels spongy, something is giving.

It is barely possible that one of your soft lines is failing and starting to bulge, but normally it will go ahead and blow out.
Otherwise, you have air in the system. No matter how many times or who did the bleeding.

Hydraulic fluid is noncompressible.
After all the cylinders have moved as far as they can go, you should not be able to push the pedal down any more no matter how hard you try.

If you can, then it is air in the system that is compressing.

There are several bleeder gadgets that might help. A lot of folks have made a pressure bleeder out of a garden sprayer.

The plans are here somewhere I'm sure. The main advantage is volume and time.
You can pour about a gallon or so of fluid in, and bleed continuously for several minutes.

If you have an air bubble sitting at some high point in the system, you put pressure on with the pedal, open a bleeder.
The bubble starts moving downhill pushed by the fluid. Then the master cylinder bottoms out, and you have to stop.
The bubble move back up to where it was.

With the pressure bleeder, it keeps going.

If you put good hard pressure on the pedal, hold it, and it slowly leaks down, you have a bad master cylinder if you do not have an external leak.

It is possible to put such a large set of wheel cylinders on, that the master no longer has enough volume to fill them each time, but its rare.
 
I am running drums in the rear. Like I said earlyer I took it to a shop and they did a power bleed. They said there was some air in there but not a whole lot. I will have to look at the brake lines that could be it.
 
Ok, since you're running drums in the rear did you make sure the brake shoes are adjusted up properly? If not then the wheel cylinders have to travel further than normal and maybe even beyond their limit. When the drums are properly adjusted there should be a slight drag of the shoes against the drum when you turn the drum.
 
It could also just simply be a master cylinder that is bad now. That happens to alot of people when doing a rear axle swap. The master cylinder piston/seal is used to riding in a certain place within the bore of the master cylinder and when you swap axles and have to start a bleeding process from the beginning then the piston/seal moves beyond the area it is normal working in and any pits/rust formation within the bore tears the seal and it leaks within itself and you will NEVER get all the air out because of it. You might unbolt the master from the booster and take a look at the rear and see if any fluid is leaking past the rear seal and into the booster.
 
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