Question about compresion check.

[kcv67]

I did a compression check on a John Deere 4255 466 engine. Can some one explain the blow by on this engine? Can you get blow by through the head? I did the compression check then oiled the cylinders and that did not increase the compression so it is pointing to the head.

 

[TKingsbury]

Blow-by is combustion getting past the rings and pressurizing the crankcase. You will see alot of smoke/wind come out of the breather tube. If you have low compression readings, it can be leaking past the valves, or the cam being out of time. Although on a diesel I would suspect that last one would cause valve damage.

Travis. .