You could drain the oil into a clean container and re-use it if it is in fact clean. Maybe you are not seeing the contamination on the dipstick. I know this is highly unlikely, but the coolant is going somewhere.

If you are seeing some moisture around the pulley, I think you found your problem.

My leak was so slow and hard to ID, but once I had the pulley off the pump on the bench, it was very obvious. You would try to remove the pulley with the pump still mounted to the engine in order to 100% sure. This might be a pain in the *** though, but would eliminate the need to replace the gasket/o-ring on the pump and only cost you time and effort.

 

About 5 secs to remove your serpentine belt. Grab the water pump pulley and try to wiggle it. Spin it by hand for any noise, rough spots, rubbing.

You can't always tell if it is bad like this, but if you get ANY of those symptoms, it's 100% diagnosed as bad

What coolant are you running? If red ELC, it tends to leave "Pepto Bismal" marks where it leaks

Above your water pump is the thin metal OEM thermostat housing. A common point of leaks when it rusts out.

I'm guessing you've been slowly losing coolant and only noticed when the heater stopped working and you checked it?

 

I would also be looking at the radiator for a leak. The wifes Excursion had a slight leak several years ago I was not able to find for awhile because most of the radiator is behind the shroud and top trim. I finally found the leak to be on the upper tank on the drivers side at the crimped seal from the plastic tank to the aluminum core. It didn't leave any coolant on the ground. This is a common place they leak once I researched it given that's where ones knee goes when we get in there to wrench on the truck. I replaced the radiator with an all aluminum tig welded tanks to core so hopefully no more issues. I went ahead and recently replaced the radiator in my F350 with the same unit even though it was not leaking because of this.

 

bwguardian, do you have a link or source for the radiator for future reference?

 

I got them on Ebay. When I replaced the one in the Excursion they were plentiful. Then last year I went to look for one for the F350 and nada. They finally started showing up again and was able to pick one up. I paid a little more because they just hit the market again but you should be able to find one for $200-$225.

I understand after researching that Silica quit making them, which was the reason there was a time they were missing in action. If you put them side by side, they are purdy much identical.

Be forwarned though...the companies that offer these are fly by night. I went back to buy from the same company that I got the one for the Excursion and they were nowhere to be found. I am not too worried about it because if it has issues, then a simple touch up with a tig can be done.

 

I'm going to take everybodys advice at five tonight after work gets done. The coolant hasn't come down off of the max level since i shut the truck off earlier today. I'm going to first pulley the serpentine belt off and check for play in the water pump, brakleen all around it and dry it off nicely. If i don't see anything there I'm going to drain the oil and check for contamination there. maybe only some coolant is going in the oil and the majority is going out the exhaust pipe. I would think I'd of seen a tanish brown slushy by now but who knows. We will know more at five when i get these tests done. Thank you everybody! p.s i fixed the thermostat housing leak last year, right now as i type this I'm waiting for the silicone to dry on a 2002 f 350 housing i just replaced and fixed due to a leak. this leak was very evident though. and i'll check the radiator for leaks too although it only seems to leak when the truck is running..

 

We look forward to what you find. We like to help those in need and appreciate you taking the advice of the collective and look deeper into the areas you may not have thought of, or you discount quickly.

This is what makes the FTE a great place to be every day.

 

What level are you having to keep topping the coolant to for it to remain full since you refilled? These trucks seem happier with the actual coolant level an inch or so lower than the full mark on the degas tank.

While this doesn't explain what happened to all your coolant in the first instance I am just making sure we are not needlessly tipping off the degas bottle just to keep the system "full"

 

I found the culprit. I pulled the truck in skipped pulling the serpentine belt off to test the waterpump. I went right to the drain plug and pulled it, I just had a feeling I guess.

 

Coolant must be going out the exhaust and into the oil because I don't think there's three gallons in there, either way, heads have to come off..do you guys think I should be worried about a warped head or anything like that? I know this is kind of rare beyond rare but still. Does a write up exist for a headgasket job? Any hints, tips, tricks? Only thing im realistically worried about is a warped head or something like that you know? anyway, I'm going home to have a few mixed drinks and think about this for a while.

 

I would have the heads milled to make sure you have a straight surface. Also while they are off, I would clean the tops of the pistons and any ridge that may exist at the top of the cylinder bore. If I were doing this, I would replace all the injector cups, injector o-rings, glow plugs, etc. I would also go ahead and have the injectors tested.

 

Newb question...

How do you know it is not the oil cooler?

I've been trying to follow along, and do not see the logic pointing to a head gasket as the only possible source.

 

Not a newb question at all. I did ask earlier what the symptoms of a bad oil cooler would be?? even if it isn't my issue, a break down of it would be good. i can tell you i do have..some type of a fluid leaking where the cooler meets the water pump. oil, coolant? couldnt tell you yet, and it is very very slight. but there is fluid leaking at a seam of the cooler near the waterpump. a few years ago i had my turbo go bad passing a chevy, the turbo shaft literally broke in half. and they say to change the oil cooler after a turbo failure...which i didint. i bolted on a gtp38r and continued passing chevys...but would a complete oil cooler failure cause oil to mix with the coolant? the oil is not making a huge tan slushy like ive seen on gas jobs but...would a complete oil cooler failure cause coolant to mix with the oil?? and, if the headgaskets are bad... i definitely will change the injector cups, the injector o rings, the glow plugs, theres a machine shop nearby, i'lll have them checked. i'll clean off the pistons, any ridges or anything i see. do her right ofcourse. as far as testing the injectors...i'll run hot stuff through them first and pray that cleans them up. i just replaced one a few months ago anyway chasing a noise. Thank you very much everybody! I appreciate everything, and to be continued!

 

I'll buy a new oil cooler and not even do a rebuild if you guys have a way to identify a cooler failure.

 

I would pull the cooler and do an inspection of the gaskets and orings on the cooler..

5 bolts and it slides right out, smack both ends off with a mallet.

Head gaskets are extremely rare in a 7.3... oil cooler... more common. Just did mine yesterday, takes a couple messy hours. Hardest part is reassembly. Entire kit costs like $20 shipped to your door.