Run a compression test to see if it is the head gasket. Otherwise, if this is a 4cyl R-engine, then it will be the front timing cover because the guides were not replaced after they wore out and the timing chain has gone right through the housing and into the water port.
Moisture in the crank case will produce a white mayonnaise substance on the cap.
I am not sure about the yellow coloring. Must be rust or something......
