2002 lb7 175,000 miles. it appears i am losing coolant up by my intake gasket towards the back of the block. i am going through about a half gallon of coolant every 150-200 miles. when i stop at night, smoke is noticeable in the head lights, how ever that has been happening for about 40,000 miles. i have only been having to add coolant for about 350-400 miles i am wondering on the proper way to diagnose the problem. how will i know if it is an injector cup VS. a head gasket etc...

EFI Live, injectors replaced 50,000 miles ago.

Thanks for any help!

I am experiencing the same symptom as well as a few more. From the many hours of research I've spent online around the forums, it seems like it is almost impossible to distinguish between a head gasket or injector cup leak. It is rather frustrating not being able to properly diagnose the problem accurately.... My truck is going in to another shop on Wednesday to see if they can figure it out. Worst case scenario, I'll have them replace the headgaskets anyways. I'll let you know what they find.

I am in the process of building my motor right now. It all started out as either a head gasket or injector cup leaking. It is hard to tell which one it is, so I took the motor out of the truck and started tearing it down. When I took the injectors out 3 out of 8 cups came out with the injectors. Turns out the head gaskets were fine. My symptoms were a hard upper coolant line when cold, using coolant (not a lot) and if you look in my coolant tank you can see what looks like soot.