'95 Jimmy-soft brake pedal

[speedyal]

Had a master cylinder replaced due to sinking pedal. Rather than be up all night in a cold garage, I had a shop do it. After pickup, pedal was 90% back, but juuuust a wee bit mushy. Old truck, figured I'd just deal with it. After hitting a slick spot and having an "ABS event", pedal is bad again. The shop re-bled at the wheels and said they verified master cylinder function by plugging the lines and it's some better, but the claim is that the GM ABS can cause a sinking pedal as it gets old. My questions: 1) Is there ANY way that a bad ABS unit could cause a sinking pedal? 2) Would an "ABS event" release any potentially trapped air from the unit? 3) Although it was reportedly bench bled, can the master cylinder be fully/properly bled while installed? 4) How do I bleed the ABS? 5) Any other ideas?
Thanks Y'all

[riptide44]

yes the abs is likely the problem - there is an ongoing campaighn for that -- the recall refers to a switch problem that sends the wrong signal to the abs - it might send a 4x4 signal when your in 2 wheel drive and vise versa - i just found out about mine the other week when i took my 92 in for a tranny flush - they said to come back and they would install the part for free - which they did - the campaighn number right off my reciept is # 99041 incorrect front axle status signal to ebc4 abs. the part and labour were free and according to the reciept the retail price was 127.00 canadian - i searched the net after this and it affects us and canadian sonomas - s10s ,s15s , jimmys etc .funny thing is the campaighn has been around for several years and i regularily have my trans flushed at the dealer who just now notified me of this ????

[speedyal]

This is a 2WD Jimmy. Any idea if this still applies?

[riptide44]

no it doesnt apply - sorry i just assumed you had a 4 wheel drive - however - you could have any number of problems - ranging from a faulty brake booster , rear brakes not adjusting , brake pads nearing the end of there life will cause this , the flex lines on the front brakes might be weak and buldging when you apply the brakes ( not uncommon on any vehicle ) . try the looking at the brake pads first .