Drain plug question - what actually is leaking, threads or mating suface washer to pan?

TiGeo

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I get weeping from the drain plug on my VW MK7 Golf Sportwagen. I have an aftermarket aluminum oil pan that uses an aluminum magnetic drain plug and single use aluminum crush washers. The recommended torque is ~20 ft lbs. Is the weep/leak from:

1) The threads (so you would say use HD teflon tape on them).

2) The mating surface where the crush washer should deform (I think?) to seal the drain plug against the pan.

Do I need to just tighten up (litterally!) and get that crush washer more deformed/tighten it more?

Don't forget folks, this post is set up on the forum using the "question" format so you can vote for the best answer with the arrows off to the right of folks' responses!
 
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Threads do not seal unless they are tapered and have an interference fit.
Thank you for clarifying...I feel a bit dumb not knowing this but I always figured it was the threads...so here, it's got to be the two surfaces mating up or in my case, not mating up well enough to seal with the crush washer. I'll have a good look when I change it next at the oil pan area immediately around the drain plug to see if it's knicked or not smooth. I also probably can tighten the plug a bit more to get that soft crush washer to fill in whatever is leaking...maybe?
 
I get weeping from the drain plug on my VW MK7 Golf Sportwagen. I have an aftermarket aluminum oil pan that uses an aluminum magnetic drain plug and single use aluminum crush washers. The recommended torque is ~20 ft lbs. Is the weep/leak from:

1) The threads (so you would say use HD teflon tape on them).

2) The mating surface where the crush washer should deform (I think?) to seal the drain plug against the pan.

Do I need to just tighten up (litterally!) and get that crush washer more deformed/tighten it more?
It's the gasket failing to seal for one reason or another. I would be curious to see that gasket.
 
It's leaking around the washer as the threads are not not like a Pipe. When I started at the euro shop I was torquing drain bolts and had several leak. Forget about the tq and tighten it by feel.
Thanks. So you're saying just use 10 ugga-duggas? 🤣

I think I'll give it another go to get it tighter this week.
 
Like everyone said, it's the washer. If you use a new aluminum one you can feel when it gets "plastic"-- whatever torque you're throwing at it will stay consistent through maybe 20 degrees of arc of the wrench turning and then it'll harden up more. Stop after those 20 degrees. It's a feel. Don't go grossly over your torque spec, you'll break stuff.

Next time you change it, compare your used washer with a new one and look for deformation. If you didn't deform it, you didn't put enough oomph into it.

Old Briggs motors for OPE used pipe plugs and those use the threads for sealing.
 
Like everyone said, it's the washer. If you use a new aluminum one you can feel when it gets "plastic"-- whatever torque you're throwing at it will stay consistent through maybe 20 degrees of arc of the wrench turning and then it'll harden up more. Stop after those 20 degrees. It's a feel. Don't go grossly over your torque spec, you'll break stuff.

Next time you change it, compare your used washer with a new one and look for deformation. If you didn't deform it, you didn't put enough oomph into it.

Old Briggs motors for OPE used pipe plugs and those use the threads for sealing.
I know that "plastic" feeling...I need to be more mindful doing this next time. I'll give it anouther yank this week. I mean the absolute worst case is a new pan, it's easy to change and not the end of the world if I screw up. The leak drives me nuts when I see it!
 
Just a month ago when I did the oil change last, I think I'm scared to actually tighten it enough b/c the pan is aluminum (but so is the drain plug).
You are smart to be wary of the aluminum pan threads. I can tell you a lot of aluminum pans have waaaaay over-torqued drain plugs installed.

Use a torque wrench and sneak up on the torque. The 2013 up Accord drain plug torque is 30 #/ft into their aluminum pan.
Was it leaking before? Was the plug pretty tight?
Good luck.
 
You are smart to be wary of the aluminum pan threads. I can tell you a lot of aluminum pans have waaaaay over-torqued drain plugs installed.

Use a torque wrench and sneak up on the torque. The 2013 up Accord drain plug torque is 30 #/ft into their aluminum pan.
Was it leaking before? Was the plug pretty tight?
Good luck.
It's always leaked since I put that pan in. I just think I'm being too timid and aluminum is more prone than steel (just a hunch). Good info on the 30 torque value.
 
I would probably give the mating surface on the pan a light scuffing with some scotchbrite and maybe also get a new drain plug. You could also try a copper or fibre washer instead of the aluminum one. I wouldn’t try higher torgue on the plug.
Next oil change I'll plan to really inspect things and do like you said, just scuff it up. If I wasn't dumb and understood this I had the pan off for a new gasket about a month ago and it would have been easy to do!

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I’ve had several drain plugs where the threads I could see were clean of oil till the drain plug pulled out of the pan. But in most cases I’d say the washer is the more important part of the seal. Check and make sure the mating surfaces of the pan and the bolt itself are flat and clean.
 
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