BurtEggley
Well-known member
- Joined
- Oct 8, 2024
- Messages
- 887
Thought I would post this in case someone is doing a search. One of my twin devilbiss built compressors has been knocking a bit near the shutoff pressure. Sounds like a rod or diesel knock, a very sharp rapping sound. It was abused by the former owner but has been good to me once I replaced the filter, changed the oil, and the reed valves, which were carbonized from overheating. I read somewhere about a month ago someone suggested double checking the pulley bolts before tearing into one, because sometimes that is the cause of a knock. The pulley bolt on this one is only a grade 5 bolt, probably 5/16", and it was pretty tight already, but I tightened it a bit more by feel. The knocking is gone, or it seems that way. Of course it was cool this morning so the oil in the compressor is thicker than normal too, but there is no hint of a knock anymore. The moral is check the pulley bolts to be sure they aren't loose because they will cause a knock similar to a rod knock or loud piston slap if they are a little loose.