Truck is a 1988 d 100 with 3.9. It is leaking antifreeze(not sure where it is going) and the exhaust smells and my heat is warm. Oil is not milky. I want to check the spark plugs soon if i can get the wires off.

 

When you say it is leaking, do you mean it is leaking onto the ground or its dissapearing/consistantly low? If you see a puddle on the ground, I would first look towards your water pump, then radiator and of course the hoses going to each. Also, a bad seal in the thermostat housing can leak.
You mentioned the oil isnt milky, but what about the antifreeze? Is it bright green or is it dull green or maybe even brown? If that is the case, I would say you are on to something with the blown head gasket theroy. Have you noticed any exhuast smoke? White haze coming from it?

 

I have had a spot on the ground a few times(today). It is low and i add water and or antifreeze more than i see a spot on the ground. I have not noticed smoke but had had a smell not sure what it smells like. Yesterday/night i bought some antifreeze and added it to it. When i left our new house to go home it was making a clicking sound for 2-3 min then went away. Heat is warm/cool i don't have dash vents. Today i looked at it and seems to be leaking at the timing chain area at the dipstick from what i could see(hard to with the alternator in the way). The antifreeze is still low.

 

if it's leaking in the timing chain area, it's probably coming from the bottom of the water pump, they are designed to leak when they fail.

 

i put a reman water pump on maybe 6 months ago

 

The mechanic said the top bolt on the timing chain cover on pass side was leaking. I had the gaskets and ha him put a new timing chain an pulleys or whatever that part is on. Now i need to change the oil. Got it back Thur seems fine but wanted to cut off a few times