guys good evening..

i have a 2000 model frontier 4x4, pupunta kaming baguio this christmas so i did some fluid checking ng engine... all was normal naman... it was recently changed oil lang ...but then decided to clean the radiator reservoir.. may napansin lang akong parang black carbon like substance sa loob ng reservoir ko... hindi naman siya langis kasi nasa ilalim siya eh tsaka nung hinawakan ko.. hindi siya madulas.. similar to a black gulaman , parang black thing na lumalabas sa tambutso niya pag pinapa pressure wash ko yung exhaust...

normal po ba ito or theres something wrong? the pickup is totally working fine naman... wala akong nararamdaman sa kanya... one more quearry... yung auxillary fan ng pickup which is not the fanbelt driven, hindi ko pa nakitang umandar... pero pag nirerekta yung fan sa battery... ok naman? the mechanic sa casa said it will only go once it reaches a certain temperature??? true po ba talaga yun?

thanks guys....