What are the effects of coolant entering the oil?  I have a head gasket very slowly leaking coolant into the valley of my Ford 4.6L but not sure if it's getting into the oil.  The levels don't appear to be changing of either fluid and I can not see any mixing of the two.  But if there happened to be any coolant getting into the oil, what can I expect to go wrong and how delayed will it be?

I am running an Auto-Rx maintenance dose as well.  Would this at all help the situation if coolant is infact getting into the oil?

Coolant in the oil is very serious if in sufficient quantities.   I don't recall the exact rhetoric on the topic, but I believe that the incredible pressures seen on the back side of the bearing (the side without the hydrodynamic wedge) cause it to damage the bearings via some micro explosions upon leaving the high pressure area.  I can't speak in an authoritative manner beyond saying that I've seen the effects in used oil analysis (UOA).

Do a simple $22 UOA through Blackstone Labs (google it) when you next change your oil.  Look at sodium in conjunction with potassium.  I'm unsure of the composition of your bearings.  If they are copper with Pb (lead) overlay, then you will probably see elevated metals along with the potassium/sodium. 

Thanks guys. I am going to get a UOA from Blackstone this time around. I'm ordering the kit now. Will a Standard UOA Analysis suffice to detect the presence of the coolant and wear metals?

Yes. It will be clearly indicated. Not hard to figure at all. You'll see Sodium and Potassium and probably Lead. The whole thing will be somewhat dirty from a metals perspective. How much will depend on how much coolant is leaking. Some engines can tolerate years of this condition without the owner noticing.

Thanks a bunch. I ordered the kit and will be sending it in next oil change.

If the engine were to fail due to this, what parts would need replacing? Assuming I catch it early enough, I'd just have to drop the oil pan, replace the bearings on the piston rods and crankshaft and reassemble? Would anything else be affected alot?

I'm uncertain on the Ford Modular engines. Coolant infiltration is not a characteristic flaw of the engine as far as oil contamination, at least not like the GM V6 3.x engines. I'm sure it's happened, but it's not a pronounced thing. Some have reported the intake leaking due to some defective composite intake piece ..but, again, I'm not well versed on the engine other than knowing that it's got a great reputation.