I have a Linde 40T with a VW V6 engine in it. The cooling system had large traces of oil however there was no water in the Engine Oil. After draining and cleaning 3 to 4 times and running for a while it seemed to clear. After we put it back to work it again presented with oil in the cooling system and engine oil very low on dip stick. We did a compression test which came up good. Could it be the head or gasket but symptoms don't present. Any advice would be helpful.