Drain Plug Torque Values

[Crossrodes]

I recently change all the fluids on my '79 R65.  I also changed all the crush washers with ones I bought at Napa.  I torqued the plugs according to the specs in the Clymer manual.  I ended up with drips from many areas. So I drained the fluids again and replaced the crush washers again...this time with BMW washers.  I'll find out today if the BMW washers solved the problem.  But what I am wondering is whether the Clymer specs for torquing are correct for these drain plugs.  It would not be the first time I have found incorrect info in this manual.  Does anyone have the correct torques specs for these plugs for the '79?

[Mike V]

Cross,

I doubt your leaks are being caused by inaccurate torque values...just a guess.  Careful not to overtorque any of these plugs, sorry I had to mention that - not to insult your intelligence.  I would check the gasket surfaces carefully to make sure they are clean and there is no debrit or burrs preventing a solid seal on both the case and plug surfaces.  Also check the crush washers carefully, I've experiened some mysterious different sized crush washers lately in diameter.  I would recommend OEM washers, who would ever think a simple aftermarket crush washer wouldn't do the trick but it may be the sizing of your local APS washers aren't correct.

I recently had a small leak in my final drive plug with a new washer. I carefully hand milled a new washer and it seemed to do the trick.  An excercise in minutia that I never encountered before.

I purchase all different sized OEM crush washers in bulk from airhead friendly shops to keep on hand and redily available.  I hate wasting expensive hypoid or 20w50 due to a $0.25 washer.  Argh.

Let us know what develops.

edit: forgot to mention I attached my torque chart herein.  Normal caveats apply, happy to share but - use at your own risk.

[Luca]

Crossrodes,

Perhaps this is not so applicable with your drain plug, but there is some useful information from Snowbum on torque values.  I'll paraphrase:

BMW has made a handful of errors in publishing ft-lb torque values that were converted from Nm torque values.  The Nm values should be OK.  Both Haynes and Clymers have sometimes copied BMW's mistakes, so they should also not be trusted.

You can read the whole book in his technical articles list at www.bmwmotorcycletech.info , currently article No. 71A

[Barry]

I too think more torque is not the answer. With steel plugs in alloy casings there is the possibility for stripped threads. We have had reports of stripped filler or drain plug threads several times here.

There can be a range of answers to  "what are the correct torque values" because many would argue that the official figures are unnecessarily high. These are not safety critical items in the mechanical integrity sense although a leak would be an issue.  They should be tight enough not to leak and need be no more regardless of the thread size.  What I'm getting at here is BMW may have looked up the thread size in a table and picked a value that the materials could take but that torque may not be really needed.

As an example Rear drive oil filler plug recommended  torque 21 - 23 lb ft. Without reference to any other figures my immediate instinct is to say that's way too high. Mike V's chart which I think takes a more experienced common sense approach suggests 10 lbft and that's what I use. In fact I see no reason to exceed 10 lbft on any of  the drain or filler plugs with perhaps a little less on the drive shaft items which are easiest to damage. With good joint surfaces and crush washers (not necessarily new ones) I don't have leaks with these figures.

I was going to add "and they don't fall out" but in 1971 following an oil change on my Ducati single, towards the end of the compulsory test ride I felt the rear tire stepping out on every turn. Just as I pulled up the drain plug fell out and deposited the whole contents of the sump on my Dads driveway.  I guess that could have been safety critical in more ways than one.

[Mike V]

Barry & All,

To qualify my chart; a lot of these items I never use a torque wrench for; spark plugs, drain plugs, valve adjustment nuts, etc. and the like.  I was filling up space and logging data as a cursory and general idea (mentally).  I think you can pick out the items that are of importance and the ones that teeter on silly or even obsurd.  And yes Barry, you are correct - I'm on the coservative side of things when it comes to torque.  In fact I actually communicated with Oak and Bum regarding these values and made minor adjustments to my chart based on their recommendations and opinions.  With practice you can develop a feel for the correct torque with some thought for practical hardware applications.

Bum's site has a much more coprehensive list of values than my chart.  But as I stated earlier the chart was originally developed for my own personal use - then amended and items added as time went on by request.

Be careful with things like spark plugs, drain plugs, valve cover acorn nuts, pan bolts, and oil filter cover bolts.  They can strip easily when using gorilla force and an un-sympathetic approach.  Be deliberate with your wrenches and pay attention to the feedback being transferred from your wrench to your hand.

We could drag this on for some time - use common sense or get the feel of a specific value then try to duplicate by hand.

Barry, I've had some oil cleanup experiences myself.  Last year I forgot to install my transmission drain plug before refilling.  A very humbling experience.  Love the smell of hypoid!  My wife doesn't share the same opinion.

[Crossrodes]

Thank you all for the torque info.  After I installed the new crush washers last night/this morning.  There were no more drips except for the rear drive.  The surfaces of the stud and the drive housing seem to be OK.  So what I have done is install some gasket seal as well as some teflon tape on the threads.  I'm going to let it sit overnight before I fill it once again with oil.  So I'll let you know how it works out.