I just bought a 2003 Lincoln LS. /the car overheats very quickly. when I removed the water filler cap on the thermostat housing there is milky looking goop in there. The crankcase oil is spotless. The car runs perfect before the temp goes up quickly. The check engine light comes on and the car immediately has zero power. I don't think it is a head gasket because the crankcase oil is beautiful. Someone said that there may be an internal oil cooler in the radiator? Any ideas?

could be a cracked head that will put oil in to your coolent system and a head gasket can do the same. The internal oil cooler is ussaly for your trasmission as far as i remember

water filler cap on the thermosat houseing? are you sure you are not talking about the radiator?

just because the oil is clean doesn't mean that the headgaskets aren't bad. There is oil valleys in the heads and coolant valleys. sounds like it's pushing oil into the antifreeze. Do a cooling system pressure test. Another way to test is a cylinder leakdown test and or do a compression test

just to answer ron... yep, weird but true..water fill cap on top of thermostat..and another on coolant resevoir... and a crazy bleeder valve.. seems this v-8 has issues with air in the coolant system

Yes this car is odd , I'm having oil getting in my coolant and my has oil cooler on it an I was told just by pass it , so how would I do that

you should not bypass, but instead replace, the oil cooler. it is at the location of the oil filter, and has coolant lines. it could well be the source of oil in your cooling system. I have an 03 LS with Sport V-8, and never heard of such 'til I tried to buy the oil filter, and found that A. the normal places don't even stock either filter choice, and B. the lookup book specifies a certain one if equipped w/oil cooler. Truly an odd car to get replacement items for. Haynes Manual? Hell no! Fun to drive? Yes, In a BIG way!