1988 dodge d100 hg

what are tall tell signs of a bad head gasket? i know if u see a lot of white smoke coming out the tailpipe and if the oil has a gray and oil mix on the dipstick. what else do i look for or what will the truck do if i have a bad head gasket? i found some white or gray fluid in the oil fill cap but when i did a oil change there was no antifreeze on my oil. so any help would be great ty.

there is no oil in the antifreeze, it dont over heat. the motor was rebuilt so could it be just some left over white fluid from the rebuild still in the motor just curculating and if so is there a tes or somethingi do to see if i have a bad head gasket?

That gunk under the filler cap is normal for engines that take lots of short trips where they do not fully warm up for any length of time.

Its just residue from blow-by gases and condensation (moisture). These accumulate in any engine, but are usually boiled off and sucked up through the PCV system when a car is driven on longer trips. For shorter trips, the oil simply does not get hot enough to really 'boil-off' these contaminents, so some accumulate under the cap.

If this really concerns you, go on a few longer trips, or, simply change the engine oil more often, say every 2000-3000 miles or so.

ok ty for that. one more question where the oil dipstick goes in to, the tube every once in a while builds up white or gray liquids too. would that also be moisture ? when i check my oil with the dipstick tube cleaned out theres no white when i dont clean it it theres white fluid liek i described before every once in a while. so pretty much its the same thing as the white under the cap?

what if i find that stuff in the hose connecting the pcv valve to the air breather or was that what u were saying earlier