1993 Chevy G20 High Top Conversion Brake Issues
 

6 Months with same mechanic and still same issue. FINALLY the problem occurred with the mechanic driving it. They are perplexed. Three master mechanics. Any Suggestions Welcome! I've owned this van for a year. It sat for a while before my purchase so many upgrades and repairs. The engine and tranny have about 50,000 miles on them. The remaining issue... Brakes: They have replaced 5 master cylinders, one proportioning valve, brakes and all important parts within brakes have been replaced. STILL it will drive for around 100 miles working great... then the brakes will go to near the floor and the brake light will come on. It is not giving a code I am told (they do have an OBD1 tester). The ABS light does not come on. The van is able to stop with the little brakes I have with added distance. They advise me they have bled the brakes according to GM ABS instructions and advise no air. They have checked all soft lines and advise are working properly. Fluid is draining through all lines as expected. What would cause this issue? What would cause 5 master cylinders to go out? Any suggestions will be appreciated!! These guys will stand by their work so they have my van until fixed.