Originally Posted by davidpm
No venting from the crankcase overflow tube.
something wrong here if i understand you correctly - if the engine has bad compression due to cylinder wear you will get blowby showing up in the crankcase vent. given the symptoms you describe-low compression and overheating - are you sure you don't have a bad head gasket? (although they will usually show one or two bad cylinders). how confident are you regarding the compression test? an easy start for a low compression diesel engine is an oxymoron.
a worn-out engine will generally let you know by smoke and hard to start. the big factor determining if it's time for a rebuild are the hours and years on it.