I wound the truck out tonight to pass somone. I wasn't paying any attention, but the when i was pulling into my neighborhood I noticed that the water temp was in the red. even with the truck idling, it wouldn't cool down. I shut it off and let it cool down. the collant level is fine, but when I opened the radiator there seemed to be a black greyish sludge. It was too dark to see well though. The coolant is good because I just changed the thermostat/ coolant a couple thousand miles ago. Could a blown headgasket push oil into the coolant and somhow cause it to over heat?

If so it's getting studded/ marine gasket/o-ring

 

check for water in the oil. water will most likely get in the oil vs oil in water. oil will appear milky if it has water in it.

 

the truck is like 2 quarts low on oil from yesterday and there is a black sludge in the radiator.

 

wow 2qts from yesterday? im assuming you didnt drive enuff miles in one day to use that much oil, so i am prolly wrong.
usually water gets in the oil, but sounds like its the other way around this time. have the cooling system pressure tested. headgasket prolly went bad.

 

I'm hoping that someone will add to this, because I know that you're not supposed to run the CTD with the cap off of the radiator...

On gas engines I would remove the belt in order to deactivate the water pump. Then you can yank the thermostat or get a hose that's high on the cooling system to watch for bubbles while someone fires the engine up. Bubbles will indicate a cylinder leak/head gasket into the cooling system.

The challenge here is that there is a valve on the CTD cooling system made to purge air. I don't know enough about how to bypass this, but I do recall potential damage being done by operating the engine without the cap on...

Hope this stimulates a better response

 

Nobody mentioned the oil cooler. Oil pressure is usually 30psi at idle hot, much higher at higher rpm's. Coolant is 16-17psi max. It will push oil right into the cooling system.

 

Good one.

Wouldn't be the first one to have that happen!

 

A simple combustion gas leak detector kit is available from your local tool truck or parts store and that is the easiest and fast way to tell if you blew a head gasket or not. i think my snap on kit was like $40 or $50 so nothing to horrible on the pocket book.