95 Blazer, No Rear Brakes

[nova72]

Hi, I have a 95 Chevy Blazer that had a brake line going to the back of the truck rust out. In the process, the brake warning light came on. I replace the brake line running to back of the truck, the distribution block at the rear axle, and the lines running to the wheel cylinders. I ended up replacing the rear wheel cylinders because the bleeders were rusted in. I bleed the rear brakes. No air appears to be coming out of the bleeders any more. The brake pedal is firm but lower than before, but the brake warning light is still on and I have no rear brake pressure. Is it possible that the combination valve is stuck or frozen? Could I still have air in the rear brake system?

[MT-2500]

Originally Posted by nova72

Hi, I have a 95 Chevy Blazer that had a brake line going to the back of the truck rust out. In the process, the brake warning light came on. I replace the brake line running to back of the truck, the distribution block at the rear axle, and the lines running to the wheel cylinders. I ended up replacing the rear wheel cylinders because the bleeders were rusted in. I bleed the rear brakes. No air appears to be coming out of the bleeders any more. The brake pedal is firm but lower than before, but the brake warning light is still on and I have no rear brake pressure. Is it possible that the combination valve is stuck or frozen? Could I still have air in the rear brake system?

When you push down brakes does fluid flow out both rear wheel cylinders?

[nova72]

Originally Posted by MT-2500

When you push down brakes does fluid flow out both rear wheel cylinders?

Yes, when I bleed the rear wheel cylinders, I can get fluid flow from both.

[MT-2500]

Open bleeder and see if it still has pressure or fluid flow.
And try a rebleed.
Also make sure rear shoes adjusted up good.

Is it 4W abs brakes?
If combination valve stuck closed you will not have pressure to both front and rear wheels.

[nova72]

Originally Posted by MT-2500

Open bleeder and see if it still has pressure or fluid flow.
And try a rebleed.
Also make sure rear shoes adjusted up good.

Is it 4W abs brakes?
If combination valve stuck closed you will not have pressure to both front and rear wheels.

Yes, it has a K-H 4WAL abs system. My understanding of the combination valve is that if the rear circuit fails, the valve will limit pressure to the rear and allow full pressure to the front.

[MT-2500]

Originally Posted by nova72

Yes, it has a K-H 4WAL abs system. My understanding of the combination valve is that if the rear circuit fails, the valve will limit pressure to the rear and allow full pressure to the front.

Also it can limit pressure to the front.
Three thins will give you a red waring light .
emg brake or low fluid if you have a low fluid switch.
If red warning light is on for a test on it unplug it from the combination valve and see if light goes off.

That system is hard to bleed.
To bleed you need 3 combination valve depressors to hold valves centered.
If air has got into the ABS unit there is 1 or 2 internal bleed valves you need to rotate to bleed thae ABS system.

Make sure rear wheels are adjusted up good .

Then Try bleeding all 4 wheels and see if you get good pressure to all 4.

If you can get the three combination valve depressors to aid in bleeding.
Also.
If all else fails get a All data online sub or a factory repair manual on bleeding.
http://www.alldata.com/products/diy/index.html

They have the instructions for the internal bleed valve bleeding.

Good Luck

[nova72]

Problem solved. I bleed more air out of the rear brake lines using a pressure bleeder setup instead of manual pumping of the brake pedal. I also readjusted the brake shoes tighter after fixing the seized brake shoe adjusters. I had rear brakes then but the brake warning light was still on. I had an assistant sit in the truck and push down on firmly in the brake pedal while tapping on the side of the combination valve. No change. I started the engine and repeated. The brake warning light finally went off due to the extra brake pressure from the vacuum power brake booster.

[MT-2500]

Yes somtimes air can be hard to bleed out of system.
Thanks for posting back the fix and how it went.
Good Luck