Hey guys seeing if I can get some help. Picked up a 2005 sullair 260 cat air compressor that was running. Ran in for an hour or so and noticed the compressor shaft seal was leaking pretty good. Tore it all down and pulled the compressor, Sullair couldn’t get me a part number for the shaft seal so measured it all out and went to a specialty seal place and got a replacement with all the same measurements(took 2 weeks to get it) Threw it all back together put new sill air fluid in the tank and started running it with no issues and no leak. Turned the machine off and noticed a squeal and then the compressor started leaking oil out the front cover again like it was pressurized. Checked my fluid and it had a slight foam to it but went away. Once there was zero pressure in the system leaks stop, fire it back up and works fine will run with no leaks but as soon as you shut the machine off it starts shooting oil out again. Any ideas? Is there supposed to be a check valve to make sure pressure doesn’t back feed? The shaft seal I put in wasn’t a whole lot different than what I pulled out. Plus sullair oil isn’t cheap so I’d like to not shoot it out all over my garage.
I would be having a close look at the input shaft play. Get a dial indicator and check radial and Axial shaft endplay. Ie: up and down (radial) and in and out (axial). There is no good reason it should barf oil out of the input shaft seal. When a screw compressor shuts off it should have a check on the inlet to stop backfeed. Otherwise it will spin violently backwards until the pressure equalizes on both sides of the rotors, and in the process pump a bunch of oil into the air inlet side. Unfortunately, when they start having seal issues alot of the time its because the thrusts are pooched. This will be found with the dial indicator and show up as excessive axial shaft play. Assuming your compressor doesn’t have a increaser gear box on the front of it, you should see very little to no axial play. Like maybe 0.004” ish hopefully less.
Also, its normal for alot of foam at shut down. You could also look and price check oil from petro Canada if you have access to it. I usually run Compro XLS in any screws I work on. From what I recall Sullair is stupid expensive for oil. Not that Compro is cheap, probably in around $300 per pail, maybe $350.
Hey thank you for commenting! Just put fresh Sullair awf in, pulled the air end out today and have no noticeable play in the shaft but I suspect the cheaper china seal I put in isn’t helping so I did order an oem one… not cheap!! $350 for the seal… But going to see how the oem seal does because it didn’t have this issue before. It was just leaking when running before but didn’t notice it leaking when shutting off, could have missed it