2001 F350 w/135K. Just put 1 1/2 gal coolant in it.
Should have been checked last oil change 2-3 thousand miles ago.
How or where can/does the 7.3L burn water?
Isn't there a O-ring on the injectors or something like that?

 

Yes there are injector orings and there is a common issue with the injector cups cracking.

Do you have fuel in your coolant?

 

You can also lose coolant through leaking o-rings in your oil cooler on the driver side of the engine block. To check for coolant in your oil, just let the truck sit overnight and then drain about a pint out of the sump... if you have a brown "milkshake" looking substance (or even just plain coolant), then you will have identified a problem with those oil cooler o-rings.

 

Also, try running the truck for just a few minutes and then let it sit. Basically just enough time to get the coolant warm and expanding but not get the engine hot enough to evaporate it if it's simply spraying out somewhere. This situation has kicked my butt on more than a few occasions.

 

One other thing I found one time, after doing the Ranger mod (vacuum valve in the heater hose for positive shutoff when using my A/C)... I did the install during the summer and used the old conventional worm clamps. When everything cooled down (i.e. contracted due to cooler ambient temps) that fall/winter, I developed a slight oozing leak at one of the hose connections on the new valve. Was not enough of a leak to ever show on the driveway, but as the system got under pressure while I was driving around, it squirted out about 1.5 gallons over a couple months' time frame.

 

Back again . . . just put another 1/2 gal. water in it. It dropped from "full cold" to "add cold".
That's 2 gallons in a little over a month! Oil is not "milkshakey", no visible leaks on ground or hoses/plumming.
Runs fine. Gas mileage seems normal . . . 12 - 15 MPG average.

 

Consider pressure testing the cooling system with the engine cold. This often reveals hose connections that don't seal well when cold. Eventually, you will need to add more coolant additive, if you're not running an ELC coolant.

 

Mine does this. I add and add, but it keeps landing on the same spot on the bottle. I know this because I marked the spot a couple of months back. The coolant level parks on the same spot, but anything added above that point must go on safari for the missing socks from the dryer or something.

 

I KNEW IT!!! And I thought I was going crazy. They are in cahoots with the socks!

 

How do you do that?

 

Wouldn't you not see the milkshake on your dip stick if you had coolant in your oil?

 

Pressure test cold...

My old 6.4 had a leak that wouldn't show. But if you drove it for 10 mins it would. Anything over that and the coolant would evaporate off the side of the radiator before it spotted on the ground.

 

That's what I would think. Dipstick is beautiful. (not my brother-in-law, the other one).