As Rex said, try pushing the fluid backwards. I fixed my problem bleed with four big C clamps on the calipers.

 

Here is how I finally got this system bled.
Using help pumping on the brake I. Bleed the master cylinder, then the pro portioning valve ( small brass pin at back of valve). Then I used a vacuum pump and bled all four wheels bleeding longest line first.

Finally use scan tool to bleed system and firm up the pedal.

Persistence. No short cuts. This is the order that I found fixed the problem on a hard to bleed system.

 

I am about to replace my own 98 Blazer 4x4 rear brake line (rusted right near tranny cross member).

Can you please explain what you did with the pin at the proportioning valve? Pushed it it? What did you use? Do you need to hold it open some how?

How exactly do you use a vacuum pump to bleed the wheels? Do you draw the fluid from the bleeder screw WITHOUT pumping the brake pedal?

I do not have a scan tool so I am not sure how I will properly finish bleeding the brakes.


Thanks for any info!

 

i always hear talks of needing a scan tool for s10s, i have done probably a hundred or so brake lines, master cylinders, whatever on these trucks and have never needed a scan tool. i think it just helps. a lot of times when you replace the rear line leave the lid on the mastercylinder it wiill sometimes prevent all the fluid from coming out and causing the master to go dry.

and spray down your rear brake bleeders with some rust penatrating oil, they sometimes brake

 

It's a good tip. I already sprayed with PB Blaster yesterday and again this morning. Bought a plug too, to prevent master from draining.

 

I used a right angle pick and a small pry bar to push in the pin while a helper pushed on the brakes to reset the proportioning valve.

For the vacuum pump I used my a/c vacuum pump and a Brake bleeding setup that has a sealed canister with two hoses. One goes to the vacuum source and the other goes to the open bleeder valve. Fill the mc with fluid and suck it through.

 

when my calipers failed and drained the system, I was able to reset the valve by mashing the pedal a couple times after refilling the master, then just bled as necessary.

 

Similar problem: 97' Blazer with leaking rear brake line. I replaced the whole line from the ABS to the wheels, but can't bleed the rear brakes.
I think it is the proportioning valve, but this does not have a separate one, I think it is in the ABS module. I looked at a 96' workshop manual, and it shows a separate valve. I can't find a workshop manual for the 97'.
A scan tool capable of "auto-bleed" can be had for about $160...but I'm not sure it will reset the valve.
I've tried a number of the different suggestions, but nothing works so far.
I thinking of using the compressor to put air pressure in the rear line to push the valve to the neutral position, but then I'll for sure have air in the ABS.
This link for the Kelsey-Hayes 4AWL shows a separate proportioning valve, so it doesn't cover this problem. https://www.aa1car.com/library/abs_kelseyhayes.htm

Any suggestions?
Thanks!

 

On my 97', there is a rubber cap on the engine side of the ABS module, that covers an odd looking tube with a rounded pin in it. The pin will push in with some good effort, and while I can't say exactly what combination of pushing in the pin and pumping the brakes reset the proportioning valve, but I suddenly could bleed both rear wheels.
I had a bid going on Ebay to buy a scanner that would "auto-bleed", and while I always like a good excuse to add a tool to the garage...when I finally got the problem fixed, I was happy to be outbid.
But it's good to know a scanner is available for about $160 that will do the "auto-bleed" routine.
Who knows...I'm not out of the woods yet. I won't be able to test drive it for awhile...looks like I need to replace an axle seal first.