Torque for bypass plug?

Jkkinz · #1 05-14-2011, 08:16 PM

Can anyone tell me what the torque is for the oil cooler bypass plug? It is the one that is safety wired beside the oil breather tube on the accessory case

Mel · #2 05-14-2011, 08:24 PM

Torque limit for the oil cooler bypass valve is 300 in.lbs.

Scott Hersha · #3 05-15-2011, 07:51 AM

Is that the cap (bolt) with a copper crush washer under it, and do you have an oil filter adapter with a vernatherm in it? If so, it is a cover over where there used to be a 'viscosity' bypass valve and spring, that is now not needed because of the vernatherm - unless you want to get rid of the vernatherm and replace the bypass valve. The crush washer should be replaced whenever you take this bolt off. I'm not sure it can be heat treated and re-used like spark plug gaskets can. If it's this crush washered plug you're talking about, the correct torque is to tighten until the shoulder of the bolt contacts the washer, and then you turn the bolt another 'X' number of degrees (crushing and sealing the washer). The number depends on the size of the bolt and the thread count - I think it's something like 230 degrees (about 2/3 turn), but not sure. I have a table with these different limits out at the hangar, but I got them from somebody on this website, so maybe someone can chime in and help out. If it is over torqued, it will eventually leak.... ask me how I know.... If this isn't the bolt you're talking about, then it's probably the one Mel is referring to. If it is, let me know and I'll see if I can get that torque table for you.

DanH · #4 05-15-2011, 09:19 AM

Figure 917 in your Lycoming overhaul manual calls for 300 in-lbs as Mel said.

The "angle of turn" method is apparently used when an asbestos-core crush washer is brand new. I've attached the torque chart for those (right click and save). If re-using an asbestos washer I'd go with the 300 in-lbs.

That said, the seal washer part number is 06E19769-0.63. Is that an asbestos-core washer?

Jkkinz · #5 05-15-2011, 06:38 PM

Thanks Mel and Dan, that is what I was looking for

Scott Hersha · #6 05-18-2011, 07:14 AM

Thanks Dan,
Mine had the copper asbestos washer and I bought some new ones. 3 RV-8's at my airport (new ECI engines all built by the same shop) had oil seeping from that bolt. We used new crush washers and the angle of turn chart and no leaks so far about a year later. I guess I got that chart from you and it's taped to the wall above my work bench. Can you reuse an asbestos crush washer? There's one under the oil temp probe on my oil filter adapter too.