Knock Knock Knock Knock Knock Knock .......help!

So is it likely the car is overheating & that's it? If the temp sensor is reading normal how can I tell if the car is overheating? I am going back to the guy's house on Wednesday to check it out better, so what do you suggest I look at? What I was planning on is checking the compression, checking the timing marks & try to get the codes off the ecu.

Sorry "EclipseTurbo" about not posting anything about myself, but if I get the car I am sure you will see a lot of me!

Thanks for your help!

PS I hope this post makes sense. I wrote in a rush.