i wouldnt worry about re bleeding them with something different.....some people dont even bleed them......they will "pump up" on their own if you let it run long enough.....check oil pressure, make sure the pressure is correct.....i dont know what it sould be....cam might be worn some...how many miles on engine.....i dont think ive seen many mitsu trucks that didnt tick at idle...lol..Actually running a detergent thru the engine might be in the right direction...oil passages might be restricted some and not forcing correct amount of oil to the lash adjusters.....