I believe it is just o rings that seal that area. You will need to remove the cooler and replace o rings and gaskets to stop the leak.

Radiator reservoir???

@@instructordave111 I thinks it's my oil cooler

@@OscarHernandez-rj1dl I would guess that as the first place to look for sure. If not there it could be head gasket, cracked cylinder head, cracked block. At least the cooler is relatively easy to test. Good luck.

@@instructordave111 That's a thing like truck never heated up

@@instructordave111 thxs

Matt was one of my students many years ago and this was what he put together for his cooling system project. Do you have a question regarding the video or do you know Matt? I am still in contact with him to this day.

@@instructordave111 I don’t know him I just had a few cooling questions about the DT 466

@@h22eh6 Possibly I can be of some help to you. What sort of questions do you have?

@@instructordave111 I have a 1999 international 4700 with a DT 466E engine and for some reason coolant keeps overflowing out of my overflow tank and the temperature gauge reads like it’s overheating but when I touch the engine it’s warm and not extremely hot what is causing my coolant level to rise to where it comes out of my overflow tank

@@h22eh6 Hi Omar, it sounds like you may have a bad head gasket or if the truck has an air compressor system on it for air brakes, it may be a bad head gasket on the air compressor pump or a cooling system air valve that is operated using the air system such as a cab heat diversion valve. When the engine is cold, take the radiator cap off and start the engine. Check to see if there are bubbles in the coolant. If there are bubbles you will have to track down where they are coming from. Does the engine have milky oil? This can be an indication of a bad head gasket or cracked head or cylinder liner.