So I'm new here and relatively new to fixing cars, I have a 1991 ohv 4.0 V6, some back story to help explain the situation it was my dad's truck but he passed away and we never used the truck but kept it and it sat for roughly 6 years and at some point tried to fix it up but it over heat and hasn't been touched since last year when I took over it got it running and it was losing coolant badly getting way to hot and white smoke coming out the tailpipe so I took the the heads off it turned out the driver side head was crack real bad and I to the passenger side head to a machine shop had the do the works they said that one was fine so I bought a new head for driverside replaced gaskets put the heads back on replace parts like rocker arms,push rods,lifters. New lower intake manifold gasket put it back together started it up but I was still losing coolant and it mixing with the oil again (the oil was water with the greenish tint wasnt full blown white and milky) so I had a look at it and on the back end of the lower intake manifold it there was the oil'y coolant mix coming out the back where the lower I take meets the block so I redid the lower intake because I figured I did the rtv wrong I've started it up again and now I'm still losing coolant.

So to break it down
Rebuilt from from the heads and up.
losing coolant.
Smoke comes out tail pipe on start up stops once I drive maybe less than a mile.
It's just a little milky in the oil refill cap

Sorry for the long rant does anybody have any ideas?

 

Welcome to the forum

What you need to do is to rent a cooling system pressure tester, its just a radiator cap with a pressure gauge and a hand pump
Fill the system with water or coolant
Then pump it up to say 20psi, normal operating pressure is 14psi

Then see were coolant/water leaks out, the pressure should start to drop of course because of the leak

Much easier to find a leak on a COLD engine

You can also test if head gasket is OK, unplug the coil pack, so a NO START
With pressure in cooling system of say 20psi
Have someone crank over the engine
If the pressure doesn't bounce around then heads are not leaking pressure into cooling system, but it doesn't sound like they are

Yes the 4 corners of the lower intake are common leak point on the 4.0l OHV, but usually to the outside not the valley
Also core plugs rust out, they are also called freeze plugs, they are under exhaust manifolds on the block so hard to see

 

So an update

I did a Coolant compression test and found a couple of leaks, one of the heater core the other on the upper hose and after fixing those it would stay at 20psi no issue. After that I did the test with a no start and the needle didn't bounce at all so it looks like the coolant isnt getting into the engine (yes!!!).

I have a couple of questions still though.
(#1.) Why is there still the white mucous'y stuff in the the oil cap area? (I replaced the pcv valve? Unless I bought it broken?) And I drive roughly 15 miles a day it gets nice and hot so I think it should burn off the moisture in the engine?
(#2.) Why is my tail pipe smoking it feels like it still is to much? (And it doesn't look blue'ish tinted smoke like oil is burning)
(#3.) And just in General is there anything else i should check out and look for?

 

That's your problem. 15 miles a day is not getting it hot enough, it might get your heater hot enough, and your temp gauge up, but you're still not getting everything hot enough.

You either need to change your oil a LOT more often, or go for a 30 + mile non stop trip at 50 mph or more once a week.

 

+1 ^^^^

Local weather has a humidity level so thats what your engine is sucking in when running
PCV system also sucks in that same air

Then we have the burning of Hydrocarbons(gasoline, H) in a mixture with air(oxygen, O), this makes a by-product, H2O, water, this is why tail pipes drip water

So your exhaust system has a constant supply of water vapor when engine is running, this is why exhaust systems RUST, from the inside out
When you shut off the engine the exhaust system cools down, and the water vapor condenses inside the pipes and Cats and Muffler, rusting starts, lol
When you restart the engine exhaust starts to heat up again and the liquid water is turned back into vapor, the white smoke on startup which goes away, but in cold weather you would still see the by-product H2O condensing(white smoke) as soon as it leaves the tail pipe

When engine is running the PCV system sucks in air from valve covers and crankcase, this is mostly oil vapor from "Blow-by"
There is a Vent Hose(breather) on the opposite valve cover from PCV Valve, V6 or V8 engines
This allows fresh air to come in
When you shut the engine off, it starts to cool down, and we known cooler objects causes water vapor to condense on its surface, i.e. water/fog on the inside of cab windows when its cold outside, or water on outside of a cold glass of beer when its hot outside, lol
Same happens in the engine
The plastic OIL CAP cools off the fastest, and is also a high point, hot air rises, so any water vapor would rise up and condense on the under side of the cooler cap
And cap also has oil vapor on it, so....................the white gunk

Best you can do is to make sure vent hose and PCV Valve and its hose are clear
And as 2011supercab said, if possible go for a 30+ minute drive once a week, go the long way to work, and if possible drive up a hill, that makes engine run hotter, this allows the OIL to heat up above 250degF which burns off water vapor and gasoline contaminants

 

update time I'm losing coolant again even though it held the pressure when I tested it last time and the needle didnt bounce when I did the no start. I'm still losing coolant it's down to about half in the actaul radiator and the white mucous'y stuff is still in the oil cap refill area (yet not in the dipstick?).
I rented a coolant pressure tester again to see what's going to happen....I'll give you an update with what that comes back with.

 

I did the coolant pressure test again and went straight for the no start (because I'm paranoid I didnt put the engine back together right.). I pumped it up to 20psi and no started it and it didnt bounce back and forth but it did sink down some?(idk what that would mean?) And I kept up at 20 psi and it would very slowly lower in pressure and there is a little leak on the upper radiator hose (that i replaced.) My geuss is that the thermostat housing hose is too corroded and warped to let the hose create a good seal.