Reality check on overtightening drain plugs

[philipp10]

Originally Posted By: Rand
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.


Now I know why I prefer to change my own oil. A 1/2" socket wrench and getting on it like you say is nuts. One of these days your going to strip out a pan. I just lightly tweak the bolt, probably no more than 5-10 ft lbs. Never have seen an issue and its always tight when I go to change it.

 

[Vikas]

Think rationally people! What is a typical torque spec for a spark plug? It is around 20-25 at the most. Why do you think oil drain plug would have higher torque spec than that? Which one has to withstand more sever conditions? Which one has more vibration to guard against? Which has to contain more pressure?

This is a classic case where using the torque wrench is wrong thing to do if the spec is 32 ft-lb.

 

[Doog]

Inspect the threads and try 20 versus 32. I always use new washers and snug the bolt with a box end wrench. Never leaks.

My Toyota mechanic never uses a torque wrench either.

 

[cashmoney]

32ft/lbs likely way too much. The primary reason to snug down the drain plug is to make sure it doesn't come loose between changes. I hand tighten it and then give it 1/4 turn or so to snug it hard with socket wrench.

 

[rationull]

Originally Posted By: ltslimjim

What do the crush washers for Subaru look like if I may?

There's a good picture here: http://www.amazon.com/Subaru-Drain-Crush-Washer-Gaskets/dp/B00BR3HMEQ

 

[rationull]

OK, guys -- multiple people are saying that 32 ft*lbs is too much, torquing to spec is the wrong thing to do at 32 ft*lbs, etc. The 32 is not a typo, it's listed in multiple places. This is a 17mm head drain bolt with a ~16mm thread. Even if the full 32 ft*lbs are not necessary I seriously doubt that torquing to spec is going to damage anything.

What is the mechanism by which over tightening causes leaks? Presumably stretching the threads to the point where something warps and the plug no longer seals flat against the pan? I would guess (hope) that if the spec is 32 ft*lbs then it would take quite a bit more to get to that point. Are any of you seriously saying you think that torquing to spec could do this?


Originally Posted By: philipp10

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?



I don't know either. I'm not nitpicking over a couple drops but it's not THAT much at this point.

The subaru washers C cross section, not solid like most aluminum washers that are used on other vehicles. There's a flat side and a curved side. Prevailing opinion seems to be that the curved side mates against the pan since the bolt flange is flat (matching the flat side of the washer) and the pan has a small taper that the curved side of the washer fits into. This is how I've been using them. My theory is that if the washer isn't quite exactly the right size, then the curve might not fit perfectly into the taper and maybe the washer doesn't fully crush to seal at the top of the plug. I thought I'd try reversing it next time and see what happens.

I suppose it's possible that I missed some bit of dirt on the mating surface too although I'm not sure I believe that'd be enough to cause a leak.

 

[SHOZ]

When washers are stamped out one side is rounded and the other flat. The flat side should go against the bolt or in this case the plug head.

If you reverse this there may be a chance that the plug or bolt will loses torque over time due to the washer deforming.

 

[Traction]

Never felt the need to use a torque wrench on a drain plug. I did 35 oil changes just on my 07 Camry. Used the same washer 35 times, and just snugged it by feel,like I always have. Never fell out, stripped, or leaked. It's just a drain plug.

 

[philipp10]

Looking at that washer I could see why more torque could be necessary. Very weird "c" section. Mine have always seemed like a simple flat washer but maybe I should look closer.

 

[mclasser]

All my cars have crush washers for their drain plugs. I've only recently gotten into the habit of changing them with every OCI since I found them for cheap in bulk on eBay. Before I'd use them over at least 3 times w/out any leaks. I don't want to get my beam torque wrench all oily so I never use it for oil changes. Simple 3/8 in ratchet and a slight tug w/one hand after the crush washer seats is all I've ever needed.