Main air compressor after overhaul

[neck7281]

Hello everybody. I have an issue with my air compressor Sanwa, piston, 3 stage. All bearings and piston rings were changed during DD. Honing also was made. Is it normal that oil is getting little bit dark? When I opened crankcase I found some black substance on the bottom surface, something like paste.

[popeye62]

Hello, neck7281.Could the dirt be from the overhaul i.e. not cleaning out the oil system? How many hours since the o/h? Is there any water in the sump? Microbial contamination is more like a jelly than a paste. I would clean out the sump and change the oil but keep a sample to send with your other LO samples for analysis. Check the crankcase breather is clear. Is it running any hotter than previously?

[neck7281]

Thanks for your reply! All dirt was cleaned. I'll check about hours. There was no any water in the sump. I've already cleaned sump and changed oil, will see. Temperature is also within the limit. Could it be piston rings or big end/small end bearings running in?

[popeye62]

Unlikely to be from the bearings, certainly hope not; rings/liner a possibility. Was the oil changed 50-100 hours after the o/h? Is it the correct grade of oil as specified? Is the black paste attracted to a magnet?