I missed the coolant odor in the exhaust part...pull the plugs and see if one or two of them are washed clean, and pressure test to look for visible leaks. If you have access to a boroscope you could peek through the spark plug holes while you pressure test it...

 

Pulled the plugs in it, and they all look about the same. Worn, but not bad looking. I'll post pictures of them tomorrow.

I'll pressure test it soon, but I don't see any visible leaks.

It also puffs blue smoke for a brief second at startup. This may be irrelevant, but I think this started about the same time it started using water.

Any other suggestions on what to check?

Thanks

 

Blue smoke is oil, which usually means valve seals when you see it at start up, but it could be something else. Coolant burns white, but if it's a slow leak into the combustion chambers, it may not show up in the exhaust at all.

 

I know blue smoke is oil, just strange that it started to show up at the same time as the coolant loss.

Anything that would make the truck do both at the same time? Valve not sealing? Cracked head?

I was hoping that the plugs would tell me something, but they are all in pretty similiar shape, so I wasn't able to narrow it down at all.

 

Pretty sure I figured out the problem...

Took the coolant overflow line and blew into it..all kinds of air came out. The cap is not sealing to to bottle. Tried the cap on my truck, worked perfect, no leaks. So looks like the actual bottle has gone bad. My theory is that the vapors are escaping and causing the coolant loss.

How freaking random is that?

 

So did this fix your problem with the loss of coolant or did it become something else?