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Vernatherm Oil Leak

Mark Dickens

Well Known Member
Patron
I have an oil leak around where my Vernatherm screws into the oil filter adapter. It's a 90 degree adapter. I've retorqued it to 25 ft/lbs and it still leaks. So I bought a replacement gasket and I note that, like the spark plug gasket, one side is flat and one side has a little bulge to it. Is it correct that the flat side of the gasket is against the Vernatherm flange and the bulged side against the oil filter adapter? Or do I have that backward?
 
Mark,
If it’s a copper crush washer, such as an AN900, the cut side goes against the flange and the smooth side goes against the bolt head. It’s easy to over torque these washers. The proper way (if you have a crush washer) is to tighten it by hand until it seats, then go another (number of degrees) based on how many threads per inch are on the fastener. Most of the time I’ve found this to be 135 degrees. So tighten a crush washer to seat the washer, then turn it another 135 degrees - half way between 90 and 180 degrees. If you torque it down way too tight, it will leak. I would say that 25 ft/lbs is way too much.

https://www.aircraftspruce.com/catalog/hapages/cardinal13-19792.php

http://acversailles.free.fr/documen...uire/Visserie/Joints/Copper_crush_gaskets.pdf
 
Scott, these are solid aluminum gaskets (Lycoming 76510). Just like spark plug gaskets but aluminum and larger. they have a perfectly flat side and a "rounded" side and I was just asking which side goes where. They are to be torqued to 300 in/lbs (25 ft/lbs).
 
Sorry Mark, I misunderstood the question. I?ll look in my Lycoming assembly manual today and see if I can find an answer. One of the engine gurus here will probably have an answer before I do, but I?ll research it. My cowling is off, so I?ll see if I can tell the gasket orientation by looking at mine when I get to the hangar.
 
Mark,
I don’t know if this helps, but if you zoom in on the vernatherm gasket in figure 3, it looks like the side going against the oil filter adapter isn’t flat. If so, then it seems like you had it right the first time. Apparently these gaskets are at least a little malleable like a spark plug gasket (as you mentioned), since when you remove it, you are supposed to throw the gasket away. I’ll ask a couple of my RV buddies today and see if we can come up with a solution.

https://www.lycoming.com/sites/default/files/SI1255A Thermostatic Oil Cooler Valve Replacement.pdf
 
This was posted by Rocketbob in 2011:

The right-angle oil filter adapters are bad designs, and this points out well why that's the case. On a normal oil filter housing there is a chamfer that the vernatherm face seals against. In the case of the right-angle filters, it uses the hole the oil comes in thru on the accessory case and as you can see it can never seal well against a sharp edge, let alone one that has a piece of gasket covering it. Yes you should cut away the gasket but I would expect even with it cut away the seal is marginal at best.
 
Thanks Scott...the chamfer that Rocket Bob mentions is inside the right angle adapter and the conical face of the Vernatherm is supposed to seat into that chamfer. My leak is at the gasket, so hopefully, this replacement will dry everything up. Thanks for the link!
 
Scott, these are solid aluminum gaskets (Lycoming 76510). Just like spark plug gaskets but aluminum and larger. they have a perfectly flat side and a "rounded" side and I was just asking which side goes where. They are to be torqued to 300 in/lbs (25 ft/lbs).

Washers with chamfers are generally installed with the chamfer towards the head of the bolt to match the chamfer of the bolt head/shank intersection, so I would follow the same philosophy here although in this case due to the soft alum gasket it probably doesn't matter :D
 
Another option ?

I might get flamed here, but why not put a little Loctite 515 on the washer to hedge your bet. As discussed above, the correct washer properly installed should work, but a little extra help cant hurt.
 
Loctite introduced into the oil system? Sounds like an NTSB report looking for a place to happen.
 
I was thinking about putting a thin line of Tite Seal on the threads next to the flange of the Vernatherm. It's used on other fuel and oil related threads so I'd think that could add a little more sealing without any risk.
 
Washers with chamfers are generally installed with the chamfer towards the head of the bolt to match the chamfer of the bolt head/shank intersection, so I would follow the same philosophy here although in this case due to the soft alum gasket it probably doesn't matter :D

Makes sense...that's what I'll do.
 
Per my IA and Aircraft Practices

I recall the smooth side is almost always against the "moveable" part; i.e. bolt being turned or nut being turned.
 
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