Had some spongy brakes...not bad, just wanted to see if I could improve it. Gave up after awhile, took the van in and they flushed the system. The brakes seemed to work pretty well for a couple of weeks. After this time, I noticed that the brakes were acting funny, and once stopped noticed that the front right brake was smoking. I jumped the gun and assumed it was a bad caliper (it was difficult to compress piston when changing the pads). I put on a new caliper and was able to bleed the brakes. However, when checking on the other three brakes, I noticed the back right brake wasn't getting any fluid. I even disconnected the rubber hose from the steel line and still no fluid. I followed that brake line back to the abs module, but didn't see any corrosion or kinks. On the advise from a local mechanic, I also added a new caliper to the front left side (he suggested that both front calipers be replaced if I was going to replace one). When disconnecting the old caliper, I was getting flow out of the banjo bolt. I quickly connected it to the new caliper, but now that brake isn't getting fluid either. I've tried the two-person approach...didn't work because brake pedal stays hard even when I crack the bleeder valves. I've also tried a vacuum bleeder, and tried using a pressure bleeder at the MC and at the bleeder valve. Nothing is working. I suspect that the abs module needs to be purged with a bidirectional scan tool. Unfortunately, there is no bleeder valve on the abs unit (odd engineering decision). I know about engaging the abs by skidding out on dirt, but with two non-functional brakes I'm not sure that is a feasible solution. Any advise before I drive this POS into a lake and go get a Ford?

 

Also tried gravity bleed...did nothing to help. Thinking of bypassing abs to eliminate this headache. Anyone have specific suggestions for someone who's tried everything?

 

" I jumped the gun and assumed it was a bad caliper (it was difficult to compress piston when changing the pads)." Deteriorated flex line to caliper creating a one way check valve trapping pressure on the caliper???

 

I checked for obvious damage and was able to blow through it (not the best check). I have confirmed that no fluid is leaving 2 abs port (left front and right rear). Right rear was completely dry and no work was done to it recently. The front left wheel had caliper change (fluid was flowing from banjo bolt at time of change). I quickly changed this one. There is no combination valve or proportioning valve...think abs handles it. Of course, there is no bleeder valve on the abs (seems stunningly stupid). I might try the gravel trick or just pay a guy $50 to scan and activate the valves. I'm just irritated that I can't do it myself. I might replace rubber hose lines just in case that is what started the problem.

 

I am also victim of bad flex hose acting like one way valve, symptoms like sticking caliper but caliper piston free. Fluid flows through hose fine when bleeding but resists caliper push back unless bleeder valve released. But something is wrong here.
On re-reading your post I think we need to go back a bit:
Since your major problems started after the brake flush I would question how they flushed it? Did they use too high a pressure and damage something, or got dirt into an orifice somewhere? Who did the flush, and were they qualified? Did they disconnect lines at master cylinder to get access?
I hate to throw a wrench into the works here, but LF & RR are on secondary circuit of Master Cylinder, I wonder if it's as simple as M/C needing a bench bleed (can also do on vehicle). That would also rule out ABS completely.
Only way to bleed ABS is with dealer's scan tool which expels air from ABS unit into regular braking system, then you bleed that system to finally get rid of the air, but I don't think it's an ABS problem.