Buying used without Blowby or dyno.

You might be able to extend the factory warranty. Some offer it if your still under the original.

 

Poor man's blow by test. Let the truck heat up to 160'f or more. If the engine is cold there is less blow by. Pull off the oil fill cap and see if it's puffing. If its not puffing you should be ok there.

 

You tube it. Your going to have some blow by. If you have one puff that's bad, it should mean one cylinder has blow by.

 

Light steady stream is fine. They all breathe. If it's "choppy" or it looks like your over heating when you pull up under a street lamp at night then you have problems

 

Check out Big Mack Trucks too. Lots of service bulletins and a few mack Tech's over there you can give em the vin and they'll tell you what's been done.

School yourself on injector cups.