Heres my thinking. If they have, they are shut off correct? So there would not be nice clear fluid at a significant stream coming from them when I bled. And, if they are shut off, then I would have a pedal. Because there would be resistance.
And lastly, there was no problem with these brakes until I replaced the pads. The odds of both hoses failing in one week right after a caliper and pad replacement are remote IMHO.

I did get two hoses from the junkyard just now AND a MC, just for fun. I'm going to through the MC on first.
If I were coming into this thing cold, as it sits, it would be my first choice.

Thanks,
Gary

 

Not exactly. They could be "balooning" for lack of a better term. Instead of the pressure being used to push the piston in the caliper out, it is expanding the hose, therefore letting less pressure push the piston out.

 

I agree. Possibly, but for both of them to go bad EXACTLY after I put on the calipers? Chances are remote. So its on the list, but pretty far down it. You have to remember, there was NO problem with firmness in the brake pedal before I put two calipers on..

Like I said, the local parts stores have no listing so I cant replace them with new anyway. So that's why I went to the junkyard and nabbed those.

I put the MC on, no change. Same as before. No pedal until you feel it hit the front brake system

Gary.

 

On my 2000 Blazer 4X4 there are 3 flexible hoses that feed the rear brakes. If the one at the pumpkin went bad, it would affect both rear brakes. (Also, there are two different rear disc setups having many differences including different rotors.)
The experience I've had with failed flexible lines never showed fluid contamination. Nor any outward sign that the hoses had gone bad. The hoses simply began functioning like a check valve. The 'common knowledge' was that the hose interior had failed.
There's so little volume of brake fluid pumped to the rear brakes that 'ballooning' might not be visible either.
This will be a real 'gold mine' of information when you work out the cause and solution.
Keep at it!
And share the info.

 

10-4. I'll be sure to report back. After some bleeding up at the proportioning valve and ABS, I am inclined to think there is air there. Depending on how I bleed it, the pedal changes in stiffness. Tomorrow I am going to investigate the dealer bleeding costs and possible ABS reset with the scan tool.
I just cant get into brake line theory for this issue. Again, there was nothing wrong with the pedal before the rear pad replacement and after. Only after the caliper replacement was there a pedal issue. I cant see brake lines failing at the exact time I put calipers on. Possible? of course anything is possible but unlikely. IMO. In fact in all my years of mechanical, I have personally never seen a failed brake line cause this issue.
Most every post relating to this on any forum is an air in the system issue.

I give up bleeding for the third day in a row.

Gary

 

i just came across this thread tonight.

brother, your problem is a spittin' image to my '98.

a brief insight to my issues (for you to compare);

- bought my Blazer in Dec/08.
- replaced complete rear brakes. new discs, new pads, BN calipers w/brackets (not reman'd).
- brakes good for 40K, then replaced rear pads/turned rotors last month.
- now have a "soft", sometimes "dropping" pedal. pressure doesn't drop as you press the pedal, rather sometimes the pedal goes low.

i'm thinking my MC is shot. kinda wierd & coincidental-especially since i'm not the only one who has experienced this problem. problem is, i'm kinda wondering about the bleeding of a MC with that damn 4WAL box sitting there.

i was actually thinking about doing a pressure test on the system, since, like you, i too have dumped about 10 liters of fluid through the system when i first did the calipers in Dec/08. don't think i've ever had such a troublesome system to bleed before.

i'll let you know how i make out with any of my diagnosis.

 

I noticed you said you bled the ABS unit by turning some thing with a 3/4" wrench. It doesn't take a 3/4" wrench to bleed the ABS ubit. There is a special tool you use (and it takes two) to bleed the high pressure accumulators in the unit. You can buy them anywhere from $6.00 - $30.00+ (for the same tool).
What sequence are you using to bleed the brakes? Should be RR, LR, RF & LF.
If the brake hose is collapsed inside there is indeed enough pressure to actuate the brakes but once you let off the pedal it'll only return pressure until the hose collapses again. I know from the hard way. It will lock up the brakes.
I always use a Mity-vac (hand held vacuum tester) to bleed the brakes. You pull about 10" Hg of vacuum and open the bleeder screw and it pulls the air through and out.
Just some thoights on your problem.

 

The 3/4 wrench is actually for the proportioning valve located just ahead of the ABS unit. At least that is what it looks like to me. I just used the slang term ABS unit because it is attached to it.

So this AM I took it in to a local tire store that does brakes. I scouted them out as they had a pressure bleeder service for 59.95. They replace all the fluid using the pressure method. And their method is the one with a reservoir, not the one where they have to refill your MC each time.
I figured that would eliminate the air speculation and if they failed, i could take it to the dealer for an ABS rest with their "special" tool.
They were kind enough to let me tell the mechanic everything I had done. I felt better about him being on the lookout for something else and not just saying, sorry, We couldn't fix it.
So I am sitting there waiting, dreading the outcome. Imagine dealership saying they cant reset the ABS and it needs replacement. 1000.00. Damn
So they mech comes out and says we got you figured out. What? The calipers were on the wrong side. He swapped them and they now could be bled. HA!

Now of course I put them on but here is how it happened. The calipers are a core charge of 42.00 each. I took both mine off and took them in. The girl gives me two boxes and says she is writing the drivers side on one box so I will know which one goes where.
So I am a mech that follows directions. I put them on just like she wrote down. I did make a mental note somewhere in this operation over the past few days that the bleeders were at the bottom. But I figured, I am not the GM engineer that designed these so that's that. I wrote it off as the calipers bolted on perfectly and the hose connected just like it looked like it should.

So that was it. Pedal back to normal. Had it not been for that mechanic seeing that, I would have been off to the dealership. And no one would have suspected the calipers as they were freshly purchased and bolted on.

There you have it,
Thanks to all for their suggestions. Hope it helps someone on the future.

@old skool luvr, I might suggest the pressure bleeding. The cost is reasonable even if you throw it away. I was reading threads on ABS brake bleeding and they are nightmares. Conclusion from veterans is that it is usually just air in the ABS unit and a special procedure can get rid of it. I'd look for a shop that has the reservoir method and a decent price.

Gary

 

and that was the mistake right there-listening to the parts counter employee.

and of course you took both of the old calipers off, so it would save you a trip back to return them later. sounded like a good idea.

if you were in Canada, i'd say you must have gone to a Canadian Tire (buncha wanna-be mechanics behind the parts counter.............)

 

lol callipers on the wrong side. i just came accross this thread and could have saved you alot of time because i did the same thing when replaceing my callipers but fortunatly for me once i felt no pressure the first thing i did was to check if the bleed screws were on the top of the calliper stupid me didn't do that before i put them on. having the bleed screws on the bottom of the calliper when bleeding will do nothing for you only give you a massive headake.