Reality check on overtightening drain plugs

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I've had some oil loss via the drain plug in my Subaru over the last 2 or 3 OCIs - just drips but enough to notice on the bottom of the pan when under the car. I'm hoping it's just an issue with the crush washers (which I replace every oil change). I'm going to try something new with the washer next time around to test that theory.

Overtightening the drain plug is another cause that gets cited for leaks. I'm one of those obsessives who uses a torque wrench on the drain plug, and I've done all the oil changes on this car so I doubt this is the case here. But reality check: I'd assume a pretty serious overtightening would be required to cause a leak, right? The car had a steel pan and specs 32 ft*lbs on the plug. It's possible I've "overtorqued" it a little just based on error tolerance but I doubt I've gone over 35 or so ft*lbs. I would hope this would not be enough to cause an issue...
 
What year Subaru? I know the oil pan drain plugs on my 2012 Legacy 2.5 and 2014 XV Crosstrek are super short on the threaded section. Not that that should make a difference, but there's not much to the drain plugs for sure. I've never used a torque wrench on one in ~30yrs of working on cars.

I put a Fumoto on my XV a few oil changes ago. Got an open bag one cheap off ebay.
 
What's the tolerance on your torque wrench at 32ft-lbs? +/- 10% of the torque spec won't do anything detrimental.

Are you sure you only have one crush-washer on there? Sometimes they stick and you have to scrape them off. Check the surface of your pan to ensure the washer is sitting totally flat.

I re-use my crush washers about 2 or 3 times.
 
Silly question but do you know the lubrication specification for the torque specs? Most torque specifications are for dry and unlubricated threads and should be reduced somewhere between 40 & 60% for lubricated threads. It'd be almost impossible to have a dry & clean sump plug & pan threads but I would not put it past the manufacturers to use dry torque specs.

Personally I either use a new washer or re-anneal the existing washer and then snug up the nut. Far less torque than you would think is required to seal it up.

In fact these days with Chinese copper washers I sometimes have to anneal them *before* I use them the first time.

To re-anneal the washer heat it up to a nice red with a torch and dump it in water/oil, then lap it on wet and dry to clean it up and remove any ridges. It'll be so soft it'll conform to just about any sealing surface. You don't have to quench the washer, but quenching it in water sees the steam generated blast most of the copper oxide off the washer and clean it up.
 
Not sure if this is comforting or not, but in all my years of changing oil on my vehicles I've never changed a crush washer or torqued the plug...no leaks that I can recall.

But then again, I've never owned a Subaru....
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32 lbft seems high what is the plugs diameter?
I looked it up !!! it is correct!
 
Try one of the rubber inside metal washers. Oil-Tite is one brand. They last a long time but not forever.

I do not use a torque wrench but then again never lean on it either.
 
If you have done that many oil changes you should have developed a "feel" for what is satisfactory. Yes, it isn't as exacting as a torque wrench, but feel is usually very accurate once you have tightened that drain plug enough times, especially since you have a crush washer on the plug as well when you turn and the resistance suddenly increases you stop tightening as you have correctly seated the crush washer and the plug is properly tightened.
 
It's a 2011 wrx, it's got the large diameter drain plug, not the smaller one some of the NA engines have.

I generally use a beam wrench, not sure what the tolerance is in practice but it should be reasonably accurate.

Definitely only one washer on there.

I think I have reasonable feel, and I generally just use the torque wrench as a final step. I never thought I'd over tightened it, just second guessing after seeing this. But, the subaru crush washers are a little weird so it may just be a fluke too.

The hardest part will be waiting 4000 more miles before "investigating" more deeply.
 
Originally Posted By: stevejones
Not sure if this is comforting or not, but in all my years of changing oil on my vehicles I've never changed a crush washer or torqued the plug...no leaks that I can recall.

But then again, I've never owned a Subaru....
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+1
 
Originally Posted By: Brad_C
Silly question but do you know the lubrication specification for the torque specs? Most torque specifications are for dry and unlubricated threads and should be reduced somewhere between 40 & 60% for lubricated threads. It'd be almost impossible to have a dry & clean sump plug & pan threads but I would not put it past the manufacturers to use dry torque specs.



I've just always assumed that drain plug specs are wet. It's possible that's not true, but the spec here is in line with most others when you consider the thread size is pretty large for a drain plug.
 
Originally Posted By: rationull
I've had some oil loss via the drain plug in my Subaru over the last 2 or 3 OCIs - just drips but enough to notice on the bottom of the pan when under the car. I'm hoping it's just an issue with the crush washers (which I replace every oil change). I'm going to try something new with the washer next time around to test that theory.

Overtightening the drain plug is another cause that gets cited for leaks. I'm one of those obsessives who uses a torque wrench on the drain plug, and I've done all the oil changes on this car so I doubt this is the case here. But reality check: I'd assume a pretty serious overtightening would be required to cause a leak, right? The car had a steel pan and specs 32 ft*lbs on the plug. It's possible I've "overtorqued" it a little just based on error tolerance but I doubt I've gone over 35 or so ft*lbs. I would hope this would not be enough to cause an issue...


35 years of changing oil, never once used a torque wrench or changed the crush washer. I cannot understand what you could do to make it leak. Is the surface where the crush washer smooth? Or are you just nitpicking about a drop or two of oil?
 
Originally Posted By: thorromig
Fumoto Valve -- Problem Solved!!
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+1. Torque once and done.
 
Originally Posted By: CT8
32 lbft seems high what is the plugs diameter?
I looked it up !!! it is correct!


Agree 32 ft lbs seems crazy. Gee, its just sealing in a non pressurized fluid. Back it off a bit.
 
I know your vehicle is newer, but I recently had increasing amount of oil around the oil pan. Turned out to be a crank seal. I no longer own the vehicle, though.
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What do the crush washers for Subaru look like if I may?
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The subaru crush washers actually crush. I just go till they stop crushing.. no leaks yet. I use a 1/2" drive ratchet and with my angle laying under the car you cant really get a ton of force on it. Worked fine on the old car too.

At least my 2015 was upgraded to the 17mm drain plug

the 14mm potmetal drain plug in the 2011 was terrible. I rounded it off on the first oil change from the factory where it was super tight and painted on. I then replaced it with a new one..

Later I purchased as special 6point 14mm socket that applied torque to the flats of the bolt.
 
Originally Posted By: rationull
I'm hoping it's just an issue with the crush washers (which I replace every oil change).


That's the dead giveaway right there: crush washers; they're easy to over tighten. When I worked at Toyota, we'd tighten them with dull knife blades so they wouldn't get over tightened.
 
Originally Posted By: philipp10
Originally Posted By: CT8
32 lbft seems high what is the plugs diameter?
I looked it up !!! it is correct!


Agree 32 ft lbs seems crazy. Gee, its just sealing in a non pressurized fluid. Back it off a bit.


I wonder if it isn't supposed to be 23 ft lbs with a typo in the shop manual.
 
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