Oil Drain Plug Torque in Cast Aluminum

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ctwo
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Oil Drain Plug Torque in Cast Aluminum

Post by ctwo » Sat Nov 29, 2014 1:05 pm

Howdy All,

I've run across the potential issue of stripped oil drain plug threads. This is on a new FJR motorcycle where a lot of users seem to report the problem and fingers point to the mfg. torque setting and initial assembly. I believe the bolt is M14 coarse thread (1.50?), although I have not measured it. The manual states 31 ft-lb, which is where I torqued it. Ironically, the final drive oil plug is spec'd to 17 ft-lb, and it's the same bolt - and both go into cast aluminum.

I can also verify that the factory had that bolt so tight that someone was required to hold the bike from being torqued over and I had to resort to a 24" breaker. It was a clean crack free when it broke loose and spun right out, so I feel good about that.

I found this reference, which indicates a torque range of 25 ft-lb. I'm wondering if it matters at this point if it is left as-is until the next oil change and if 31 ft-lb is likely over torqued? I've always use my best judgment on these things unless a critical torque is required, and 31 ft-lb is more than I'd torque by my calibrated grunt method.

http://mtsspecialservices.homestead.com ... l_data.pdf
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warmstrong1955
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by warmstrong1955 » Sat Nov 29, 2014 1:37 pm

M14-2.0 would be course thread. 1.5 & 1.25 would be fine.

I would guess that whoever installed the drain plug at the factory, forgot to adjust the pressure on his wrench before tightening. They don't use conventional torque wrenches.

31 ft/lbs doesn't sound excessive to me.
It would be a good question to ask the Yamahammer shop guys, who work on those things all the time, next time you're at the dealer. Often times the mechanics do things differently than the book.

Bill
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FLtenwheeler
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by FLtenwheeler » Sat Nov 29, 2014 2:53 pm

I like the torque spec in some of the older engine manuals I have looked at. The torque spec for the oil drain plug is " OIL TIGHT"

You are not holding anything together and all you are doing is keeping oil in.

Tim
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by spro » Sat Nov 29, 2014 7:25 pm

What I say is obvious so I hope it isn't taken as an insult. Don't know about your bike but generally there is a window of threads. The plug may be undercut near the head and every thread counts when that torque is applied. The sealing ring of copper or whatever material, should be the same thickness compressed to allow all full threads to be engaged.

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Re: Oil Drain Plug Torque in Cast Aluminum

Post by OlderNewbie » Sat Nov 29, 2014 8:02 pm

Sounds high to me unless a lot of threads are engaged. As a reference point, spark plug torque into Al is 18.0-21.6 foot pounds according to NGK.

John

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warmstrong1955
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by warmstrong1955 » Sat Nov 29, 2014 8:43 pm

OlderNewbie wrote:Sounds high to me unless a lot of threads are engaged. As a reference point, spark plug torque into Al is 18.0-21.6 foot pounds according to NGK.

John
Spark plugs are of a different class. Per the Champion kids, who used to feed me all the free spark plugs I could stand in return for my display of many a bunch of CHAMPION decals.... over-torquing is bad, as it can distort the body of the plug, and degrade or break the insulator. Th-e insulator is ceramic, and quite brittle.

So....spark plug torques are adjusted to avoid body distortion, and resultant performance problems... including total failure (been there). They utilize crushable washers to compensate for the lower torques to maintain a seal, although....I used aluminum washers, of various thickness, to index the plug electrode to the head. In racing....every little thing matters.....like a lb/ft of torque or a half-a-HP.....ya gotta get what you can get....

:)
Bill
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spro
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by spro » Sat Nov 29, 2014 9:14 pm

The plug is steel and the female thread is aluminum.... or is it? If everything is right, it doesn't crush the thread internally. By previous action it may be that larger torque is required. I think, along time, my theoretical doesn't apply. We depend upon items which have been altered. We need to know how they were, so we don't run a tap in there and remove the meat of the formed union . There is no "going back" when that happens.
lt would be a new pan or serious reconstruction or a kit which addressed the same thing-because it already happened.

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ctwo
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by ctwo » Sun Nov 30, 2014 11:55 pm

It's happened a lot - along the lines of a stuck chuck thread here. Most folks discover it on the second oil change after having the dealer do the first 600 mile service, which involves new oil. Some have reported the bolt is just stiff all the way out the first time, and aluminum threads come out with the steel bolt, and some find it just never tightens. Time-serts are usually suggested if one does not want to pay for a new crankcase cover.

I decided to break it loose again when it was hot and torqued it to 25. I think it's a problem introduced at the factory considering how tight mine was.
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spro
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by spro » Mon Dec 01, 2014 12:55 am

I probably should leave this. It is different with 2-cycles or it was. What we may see as over torque at a drain plug for 4-cycle is necessary with 2-cycle.

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SteveM
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by SteveM » Mon Dec 01, 2014 9:23 am

I remember arguing with a Ford engineer at the NY car show.

She mentioned that the oil pan was aluminum and I asked if there was a steel insert. She said no, as that would affect the recycleability.

I said the the owner isn't going to care about the recycleability when he has to shell out $250 for a new oil pan because the quick-change lube shop stripped the threads.

Steve

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warmstrong1955
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by warmstrong1955 » Mon Dec 01, 2014 10:58 am

As noted in a different thread....anti-seize is a good idea!

Bill
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SteveM
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Re: Oil Drain Plug Torque in Cast Aluminum

Post by SteveM » Mon Dec 01, 2014 11:06 am

warmstrong1955 wrote:As noted in a different thread....anti-seize is a good idea!
Yes, but one downside is that with the anti-seize applied, you can, at the same torque-wrench force, apply MORE tension to the threads.

It will definitely prevent the galling and corrosion issues you will have with steel on aluminum.

Steve

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