Overheated! Engine damage?

[srmauer]

This is my first time posting and I may have a serious problem. I recently bought a 2003 Ranger with the Duratec 2.3 engine. My son has been using it. We have had to add a small amount of coolant/water for the past few months (no leaking but the #3 plug was exceptionally clean-yep) but we were waiting for a more opportune time to dig into repairs. Apparently he allowed the water to get too low and the engine overheated to the point that the computer shut it down-not soon enough, though. There was water in the oil.
Here's my dilemma: I pulled the head and can find no damage. Has anyone gone through this before. I see no cracks but I have not put a straight edge on the head yet. What are your suggestions as to my next step?

 

[RonD]

Have the head cleaned, surfaced and pressure tested.
A crack in the head won't send coolant into the oil, a blown head gasket will.

The main heat in an engine is generated in the head(the dome where valves are), when coolant level gets low it makes the head hotter first, gravity being what it is
Heat causes metal to expand, so the head metal expands more than "normal", this crushes the metal head gasket ring(s) sealing the cylinders, the 1,000+ psi pressure in a firing cylinder then beaches the crushed ring(s), this pressure first encounters the cooling system passages since they surround each cylinder for cooling, this causes excessive pressure in cooling system and causes rad cap(16psi) to open and more coolant is pushed out into overflow tank, so more overheating.
The head gasket can breach even further so pressure from cylinder firing pushes any remaining coolant into oil return passages, passages that allow oil going to rockers/cam to drain back to the oil pan, so coolant in the oil pan.

A crack in the head only would go directly to a cooling passage, causing the over pressurization of cooling system but not coolant in the oil.
Although this would lead to more overheating and a blown head gasket so..........

You should clean out the oil passages and bearings as soon as possible by putting on fresh filter and some fresh oil in the pan, not full, just enough so oil pump pick up is covered, then manually turn the oil pump to push out contaminated oil, move the crank a 1/4 turn a few times to get at all the bearings.
Then drain the oil and change filter
I haven't done a 2.3l DOHC so can't be specific on how the oil pump will be turned.
I use a cordless variable speed drill with adapter to turn oil pump.

 

[srmauer]

Thank you RonD. I appreciate your detailed explanation. Honestly, I was expecting to see a crack somewhere.

I was more than a little puzzled because once the engine was cool, the truck ran fine. I was expecting to lose a cylinder due to low compression. This was not the case.

There wasn't much water in the oil. It wasn't milky white, just starting to turn a lighter shade of brown.

Steve

 

[adsm08]

The 2.3L oil pump is crank driven. You have to turn the crank over to move the pump.

Change the oil using cheap stuff, run it for a few minutes, then change again.