Coolant Overflow After Shutoff?
 

Over the last few days I have been losing a good chunk of my coolant every time I drive my truck. After I shut the truck off I can hear the coolant boiling up in my overflow and it dumps out the hose overflow down to the ground. I lose about half a gallon everytime I drive now so I am just running distilled water until I can get it fixed.

I never run over 190-210 when driving, most mornings my truck doesn't even get to full temp by the time I get to work.

I can't imagine it's related at all but I just replaced my fuel pump and filter last weekend.

What could be causing the overflow? Should I throw a new thermostat in since they're so cheap?

I checked my coolant and it's a little brown, sort of rusty but I think the guy who owned it before me was running straight water. Should I flush the coolant system out with water?

Probably needs a coolant flush. It sound like it's overheating, despite what your gauge is telling you. It's a pretty common issue.

Yep, when you refill after the drain & flush.

Could be a faulty radiator cap, (venting at too low pressure) they're cheap too.

I am going to flush the coolant today and see if that helps, I am thinking it might just be clogged. I notice when I run the A/C or any fans now it automatically goes up to 210 dead center on my gauge but never any higher.

I never overheat while driving, I thought it seemed odd to only overflow once the truck has been off for 3-5 minutes.

Thanks, I might as well replace that too since they're cheap.

So after replacing the radiator cap, thermostat, and flushing everything out I am still having the same issue, about 5 mins after I got to work today I looked out my office window and saw a puddle under my truck from the overflow. I lost maybe a quart of coolant/water today it wasn't as bad as normal.

Any ideas?

Bad water pump, plugged rad? The factory coolant has been known to have issues if it doesn't get flushed, or changed. Also bad news if you combine the green and orange coolants, they make a muddy sludge.

The last cheap thing I can think of is take the tank off and make sure its not cracked.
I know you said it was from the overflow but with any luck it could just be following that line down.