cracked crankcase around oil drain plug: my fault?

[Shenendoah_Rifleman]

Hello,

 

about a year ago I bought my DRZ, and when I first tried to change the oil both oil drain plugs were spinning in place due to overtightening by the PO and took a ton of effort to remove. I brought the bike into the local Suzuki shop to have the threads fixed, when they informed me that the overtightened drain plug had cracked the crankcase, and I'd need a new crankcase. $900 dollars later they fixed up the bike and it ran great for the last 1,200 miles.

Today I went to change my oil and the exact same thing happened with the crankcase drain plug. I was able to remove it just fine but when I put it back I couldn't get it tight and I discovered a crack in the threads... and was able to pull off the bolt hole with my fingers (see first pic). What I'm wondering is how this happened.

Is it possible that when I was loosening the bolt with my torque wrench the lateral pressure tore off the bolt hole?

Or do you guys think the shop overtightened the bolt when they put it back together?

I also tried to take the frame plug off but ended up stripping it.. it sure seemed a lot tighter than the 13 ft/lbs the service manual says.

 

Removed drain plug and piece of crankcase

Crankcase

Edited May 7, 2014 by Shenendoah_Rifleman

[Stuwy123]

DUDE! That's terrible. I'd be going back to the dealership with that one.

Edited May 7, 2014 by Stuwy123

[Shenendoah_Rifleman]

I edited it to add the rest

[k4f5x0r]

It's not uncommon that it happens, the crank case is made out of weak magnesium metals.  Did you put the crush washer on upside down and over tighten it? If the dealership was the last one to change the oil i would trailer it right back to them and tell them to fix it or they'd be hearing from my lawyer.

Be VERY careful when tightening the crank case plug. As you already know it strips easily and if tightened too much it cracks the case. I tighten mine snug with a wrench and then give it 1/4 turn just to ensure it crushed the washer completely.

Edited May 7, 2014 by k4f5x0r

[Brandon B]

I would be instantly bringing that bike back to the shop. Were you able to verify they actually replaced the cases? This seems fishy to have the exact same problem twice in a row.

[MR5627]

Not sure if they replaced just the side with the drain plug, but based on your second picture, the cases look identically worn / corroded / dirty.  Neither side looks like it only has 1200 miles on it.  What did they actually do to your bike?

 

Also, you don't remove bolts with torque wrenches.  They are just for tightening.

Edited May 7, 2014 by MR5627

[Shenendoah_Rifleman]

It's not uncommon that it happens, the crank case is made out of weak magnesium metals.  Did you put the crush washer on upside down and over tighten it? If the dealership was the last one to change the oil i would trailer it right back to them and tell them to fix it or they'd be hearing from my lawyer.

 

 

This was the first time changing the oil since the dealership had it.

 

Not sure if they replaced just the side with the drain plug, but based on your second picture, the cases look identically worn / corroded / dirty.  Neither side looks like it only has 1200 miles on it.  What did they actually do to your bike?

 

Also, you don't remove bolts with torque wrenches.  They are just for tightening.

 

What they actually did was mate the upper half of my engine to a complete bottom half (i.e. both crankcase sides plus internals) I found on ebay. the bottom half was from a bike that had about 4000mi on it, so they look about like they should (other than the crack :/). The reason I was using a torque wrench is that's my only 3/8" socket wrench. Other than being unnecessary, is it bad to loosen with a torque wrench?

 

Would anyone be able to tell by my picture of the drain plug if the washer was put on backward or tightened significantly more than it should of been?

[bmwpowere36m3]

This was the first time changing the oil since the dealership had it.

What they actually did was mate the upper half of my engine to a complete bottom half (i.e. both crankcase sides plus internals) I found on ebay. the bottom half was from a bike that had about 4000mi on it, so they look about like they should (other than the crack :/). The reason I was using a torque wrench is that's my only 3/8" socket wrench. Other than being unnecessary, is it bad to loosen with a torque wrench?

Would anyone be able to tell by my picture of the drain plug if the washer was put on backward or tightened significantly more than it should of been?

A piece of the crankcase broke off.... regardless of whether they over-tightened the drain bolt or installed the sealing washer upside-down or reused the old one or used the wrong type, whoever did the work screwed up somehow and should be held accountable.

[bmwpowere36m3]

And yes, this kind of damage has occurred to a few forum members. For any of the reasons I listed above (usually over-tightening and less so improper installation of sealing washer).

[DrzDick]

If you put up a good close up of the bolt with the crush washer on, it should be apparent if the washer caused it.

[qwaster]

Don't want to offend you but if this happened twice and your only ratchet is a torque wrench maybe you might want someone to do the maintenance because that cheap oil change just turned really expensive. Those threads on that broken piece also look flattened in one area. Maybe crossed threaded?

Edited May 7, 2014 by qwaster

[Ladyeclectic]

Don't want to offend you but if this happened twice and your only ratchet is a torque wrench maybe you might want someone to do the maintenance because that cheap oil change just turned really expensive. Those threads on that broken piece also look flattened in one area. Maybe crossed threaded?

 

The last person to touch the crank case and oil plug was the dealership, so he DID try to let someone else do the maintenance. Obviously, that was fail as well.

[qwaster]

The last person to touch the crank case and oil plug was the dealership, so he DID try to let someone else do the maintenance. Obviously, that was fail as well.

He stated "I was able to remove it just fine but when I put it back I couldn't get it tight and I discovered a crack in the threads... and was able to pull off the bolt hole with my fingers". He was the last to touch it. No dealership is going to admit fault on that. Cross threading would bust that apart real fast.

Edited May 7, 2014 by qwaster

[Noble]

My 2 cents.

 

The dealership did not replace the crush washer.  They may or may not have over tightened it. Did they ever even have the drain plug out?

Might have been cracked when you bought the motor lower end. 

You may have cracked it yourself as it seems apparent you did not replace the crush washer.  (I do not know your mechanical skills so sorry if I miss judge)

 

Comment to other answers.

Never add 1/4 turn after it is tight.  Tighten correctly and leave it

The center cases are die cast aluminum not magnesium.  Only the outer covers are mag

Bad to use a torque wrench to loosen? yes.  Because a torque wrench is a calibrated instrument and using in the reverse direction can affect the calibration. And it is just bad practice.

Torque wrenches are fine but they have to be accurate and the correct scale.  Otherwise it is just false hope for the user and you get into more trouble than you avoid by using it.

A drain plug is like a shoulder bolt.  There is no stretch.  Once it is solid, it is solid. DO NOT add a 1/4 turn.  Honda aluminum washers offer a little more safety factor to over tightening (If you use a new washer that is not already crushed)

[Shenendoah_Rifleman]

If you put up a good close up of the bolt with the crush washer on, it should be apparent if the washer caused it.

Here you go. If you left-click the picture it should open up in a new tab where you can zoom in.

 

Don't want to offend you but if this happened twice and your only ratchet is a torque wrench maybe you might want someone to do the maintenance because that cheap oil change just turned really expensive. Those threads on that broken piece also look flattened in one area. Maybe crossed threaded?

No offense taken. I'm trying to sincerely determine whether this was my fault or the dealer's. With that being said, I've changed the oil on every vehicle i've ever owned and never had a problem. I just changed the water pump on my jeep today which was a whole lot more complex so I'm not mechanically clueless.

If the bolt was cross threaded it would have to be when it was last put in the bike, since I started it back in by hand and it already had the signs of the crack when I did (side-to-side play in the thread).

 

What I'm really trying to figure out is if this damage is possible from just the way I loosened the bolt, since otherwise the damage must have been caused by someone other than me.

[Noble]

The drain plug was not cross threaded.  No evidence of that.

The crush washer appears very crushed.  If you did replace the crush washer, it may be your fault.

No, absolutely it did not happen from loosening the drain plug.

 

What did it feel like when you loosened the drain plug. Normal, loose, over tight??

 

If it was a sloppy fit when you put it in, yes it was probably already cracked and was probably not very tight when you removed it.  You could not crush a new washer that much if it was already cracked.  Does that analysis fit?

[ohgood]

that picture doesn't look like it's cross threaded. 

 

most likely they damaged it when they over torqued the drain plug, but it didn't show up until you removed the plug, which was holding it all together. 

 

 

proper torque of the drain is the MAIN ISSUE HERE, as these are not engine mounts, they're just drains. treat them as engine mounts and they'll pop off every time. 

 

 

**

sorry, but this one isn't going to be one you can win or prove fault with. take it to a machine shop and pay them to weld a threaded plug in place. then use a torque wrench until you get the feel of what <20 lbs feels like. 

 

sorry, the drain plugs are 15 and 13 ft/lbs, i quoted too high still, at only 20ft lbs. 

Edited May 8, 2014 by ohgood

[Shenendoah_Rifleman]

The drain plug was not cross threaded.  No evidence of that.

The crush washer appears very crushed.  If you did replace the crush washer, it may be your fault.

No, absolutely it did not happen from loosening the drain plug.

 

What did it feel like when you loosened the drain plug. Normal, loose, over tight??

 

If it was a sloppy fit when you put it in, yes it was probably already cracked and was probably not very tight when you removed it.  You could not crush a new washer that much if it was already cracked.  Does that analysis fit?

When I loosened the drain plug it did feel a little loose at one point, like the threads weren't catching. But it did come out without too much trouble. Unlike when I first got the bike and tried to change the oil, when the threads were so damaged from overtightening the bolt just spun in place.

 

I didn't ever touch this drain plug or its washer before I loosened it today.

 

However, you brought up a good point in your last post. I'm not 100% sure the shop ever did touch the drain plug. The new bottom end may have included one and I don't see why they would need to have touched it. It just seems that my luck can't possibly be so bad as to inherit two DRZ motors from previous owners who massively overtightened the drain plug. I'm normally a fairly lucky guy, haha.

[Stuwy123]

The thing that bothers me about this whole situation is that you were using a torque wrench.

This leads me to believe a few things:

1. You have limited tools and have limited experience with them

2. Torque wrenches are usually 12-16" long, which makes them very easy to over-torque and set the wrong way (loosen vs tighten).

3. You were using the torque because a smaller tool wasn't cutting it, i.e short handled ratchet wrench for those small metric bolts

4. You took it to the dealership. Not sure about motorcycles but car dealerships only ever tighten bolts with the pneumatic impact. I've asked to see a mechanic's torque wrench and he peeled the plastic off of it in front of me and the manager. Haha. So the bolt could have been over tightened to begin with. 

 

All these things lead me to believe you messed up and tightened an already tightened bolt to the point of failure.

Go back and check your torque wrench.

Someone has to play the devil's advocate.

[Noble]

I always have something to say often in conflict.

Stuwy - My local Suzuki dealer will not touch a motorcycle without a torque wrench.  That is not my method but it is theirs.  Protects them from claims about under or over tight.  I know the mechanic.  He is very experienced an undoubtedly does not need to use a torque wrench on every nut. But he does.

 

ohgood - Don't say that here on TT.  Replacing the crush washer every time is highly recommended here in TT.  It is a safety factor for people that like to hurk on the drain plug.  There is also the opinion that an old compression washer acts like a wedge to help crack the drain plug boss.  Yup I agree, if you know what you are doing, it does not need to be replaced probably ever.  I have never used a torque wrench on a drain plug, never replaced a Suzuki drain plug washer, never broken a drain plug boss and never lost a drain plug.  But that is just me.  I trust myself. For the less experienced, a new washer is good insurance.  I'm not a big fan of torque wrenches but if a quality calibrated wrench of the correct scale is used, that is a good thing for less experiebced do-it-your-selfers.  A 100 foot pound torque wrench set to 13 ft lb is less than useless and is an invitation to disaster.