Quincy 325 roc 13 question.

[Pileit]

Think we screwed up at the shop. My faithful quincy 325 that has never had a problem since new, now has. Sent one of the guys to get some supplies and told him to pick up some compressor oil to change it on the compressor. The store was out of reg compressor oil so he picked up amsoil full synthetic. A few weeks later we are developing blow by in crankcase. If you remove dipstick we can feel it. Is there anything besides worn compression rings or head gasket that could cause this? I was hoping something simpler like one of the valves ? Unloader? Not sure how the quincy valving works exactly. Was hoping someone may know of something to help. Maybe it wasnt the syn oil? Im guessing the thinner oil or detergents in it have caused this. Thank you.

 

[American Locomotive]

Dual stage compressors like a Quincy 325 will always feel like they have blow by when you remove the dipstick. This is because one piston is larger than the other, so as the big piston comes down, it's going to displace more air in the crankcase than the smaller piston is going to take up.

There is a line that goes from the crankcase up to the head. It usually connects in near the air filter inlet. Make sure this line is clear, as it is the crankcase breather line.

What made you think you were developing blow-by?

 

[Pileit]

The dipstick was actually out and it i heard the noise. Possibly someone didnt put it in correcly that morning? I dont beleive ive ever pulled it while running, so i dont know what normal air movement and noise it should have. I will check breather line. Thank you for quick reply.

 

[Wrench97]

We've run 10w30 motor oil in the one at the shop since 1975, it has a touch of blowby but otherwise still runs fine.