I bought a 1994 Ranger with 3.0 liter engine that was damaged by freezing temperatures when it sat outside with insufficient anti-freeze. I understand there was a lot of water in the crankcase when the engine was run after the freeze. The previous owner pulled the heads off expecting to find a bad head gasket but the gaskets and heads look okay.

I am trying to decide whether to replace the engine with one from a recycle yard or to tear the current one down to find and repair the damage. I understand there is a possibility of damage to the timing chain cover as the water pump bolts to that. Perhaps there is damage to the heads that I have not spotted, and perhaps the block itself has been damaged. There may well be additional vulnerable places that I have missed.

Does someone have experience to know where the damage is most likely to occur when an engine is put in a deep freeze without coolant protection?

 

I assume it wasn't low on coolant just had more than 50% water, because anti-freeze doesn't wear out, anti-corrosion protection in coolant does wear out which is why we change it, but the anti-freeze protection doesn't expire.

Coolant in the oil could mean cracked block assuming it froze solid, but if it was started with coolant in the oil and it has been sitting for any length of time after that then the bearings will need to be changed as they will be oxidizing(rust) from the contact with water.
You can usually clean them out if you find the leak and get fresh oil circulated in a timely manner, a month or two maximum, but if it has been sitting longer then I wouldn't trust the bearings.

So I would check around on used 3.0l Vulcan engine, they came in:

1987–1997 Ford Aerostar
1986–2007 Ford Taurus
1986–2005 Mercury Sable
1990–1992 Ford Probe
1991–2008 Ford Ranger
1992–1994 Ford Tempo
1992–1994 Mercury Topaz
1994–2007 Mazda B3000
1995–2000 Ford Windstar

You can use any of these for the block and heads, you would need to use your intake, oil pan(maybe pump as well) and accessories(brackets) for most but they should be fine to reuse.

There is no "common" place for a frozen engine to crack, it obviously would need to crack between water jacket and oil passage to get coolant in the oil, but it would be just guessing as to where that could be.
Pull the water pump and have a look

 

The former owner had lived in Texas and was working in Michigan without thinking about the importance of anti-freeze in the winter time. I suspect there was very little if any anti-freeze in the system.

I had not considered the possibility of rusty bearings. The truck has definitely been sitting for several months but I can rotate the crank easily by hand. Does this mean the bearings are okay or should I not even consider using the block without a complete rebuild?

 

Bearings won't freeze up just rust, and just like body rust, material is lost and there is no getting it back, even minor pitting in bearing surfaces will shorten its life quite a bit.

Good read here on water and bearings: How Water Causes Bearing Failure

You could have the heads pressure tested, and hopefully find a crack(weird to type that, lol, "hoping" to find a crack), but if you don't then what?
Visual inspection of water pump and timing chain cover, but what if nothing is seen?
Visually inspect intake manifold, it has a water jacket as well, but what if......?

And lets say you do find a crack..........is it the only one?

IMO, with the possible bearing issues and the unknown about where the water came from I would just look for a running 3.0l long block(assembled block and heads).

If you have the old head gaskets and head bolts, and intake gasket, you could reassemble the engine and then pressure test it to see if you can find the leak, you only need 15-20psi to test it, so old head gasket and 60ft/lbs on the head bolts would be fine for that, wouldn't cost anything but time.

 

Thanks RonD,

I was thinking of trying to seal the coolant passages on top of the block and applying air pressure to figure out where the leak is but had not thought of using the heads for that purpose. Now I'm thinking to partially reassemble using inner tube rubber instead of the original head gaskets. If the coolant cavities on the rest of the engine hold air pressure the problem must be in one of the heads.

I originally bought the truck as a beater so am okay with an engine with less than perfect bearings. I suppose after I get it running I could "fall in love " with it and want to restore it to perfection!

What do you think about reusing the original head bolts in my scenario?

I checked with a local scrap yard for a used engine. They don't have one in stock and would want $550 if they ordered one in. I missed a chance to buy a wrecked Ranger for $200. Maybe there will be another.

 

For running the engine I wouldn't reuse the TTY head bolts, for cooling system pressure test they would be fine.

TTY(torque to yield) head bolts are stretched when installed, when removed they don't un-stretch, and metal is now fatigued so reinstalling would be "iffy", best case would be if a few broken when torqued down and those could be replaced.
Worst case is if all torqued down OK and then after a few heat up and cool down cycles, this stretches bolts more, and one failed, then it would be just a matter of time before head gasket failed and all that time and money you spent would have to be done again.
For under $25 it isn't worth the possible downside IMO.
'99 and up 3.0l have longer head bolts, so make sure you get the right length if you do get new ones.