[SilverSN95]

Here is my take on bolts backing out. This will happen if it does not maintain a residual torque or bolt stretch. There are a number of things that can cause this but anything that prevents either of these two things from happening will result in the bolt backing out. Is anything stripped? Are the bolts bottoming out? Are you securing the bolts with the proper pattern/sequence and using a torque wrench to ensure proper installation torque?

Also, just a question, if you are leaking coolant into the motor wouldn't that cause the oil to sludge up? I thought any significant amount of water in oil will cause this to happen and not actually thin-out the oil.