Alright guys this is my last problem and then my truck will be running perfect.

My truck randomly white smokes the only pattern i can see is that it normally starts after its been driven for a while and the has to idle for an extended period of time. For example i went to the parts store while on the way home i stopped by the drive thru and had to sit for about 5 minutes then out of nowhere it just starts smoking. It ran the same and i put no load on the motor when it started. It stopped after about 10 minutes whrn i was back on the highway. Now a few times it has done it on start up but it doesnt smell like oil and the smoke is white but it definitely has a smell. My truck sat for about two weeks without every being turned over and when i finally started it up there was no smoke at all.

The color makes me think its coolant but i dont see any leaks and have turned it over without plugs and never saw any. I believe that the previous owner used some stop leak or something similar because my water pump and thermostat housing had a creamy colored residue that dried to a powder.

What do you guys recomend i do to find the cause of this? I have read about some sort of pressure test for my coolant system but i dont want to do it until i get a 2nd opinion on the matter.

Thanks in advance