schwett

changed the oil last night with two buddies of mine, who were doing oil changes on their cars at the same time - an '01 330ci and an '01.5 s4. everything seemed fine until i went to put the drain bolt back on. i used a torque wrench which was not mine, that i have never used before. it seemed to me that the drain bolt was turning in MUCH further than i'd have expected, and the torque wrench was not slipping or clicking as they usually do once they reach torque.

i stopped after just a bit of this, maybe a half turn past where i would have stopped if i was not using a torque wrench. i didn't think much of it until about 10 minutes later when my friend asked me to come look at the drain bolt on his 330... he claimed it just kept spinning around and it wasn't the wrench slipping, it was the bolt spinning.

he had broken the head of the bolt off. at this point, we got curious about the torque wrench. i set it to 5 lb-ft and tried it on a lug nut. it was taking all the torque we could put into it, easily 50-75 lb-ft. tried a couple settings, backed it out and back in, and NO limiting action whatsoever.

so now i am paranoid. my drain bolt it certainly not broken, and there's no leaking oil, but i MUST have overtorqued it by quite a bit, simply because it's not the kind of bolt that goes around for many (any) turns after it bottoms out on the washer.

any advise? just leave it? have the dealer pull it out and check the oil pan? pull it and replace the bolt only?

jojipoji

did u have a crush washer?

xviper

The damage has already been done but hopefully it was minimal. When a bolt is "torqued", both the threads on the bolt and, in this case the oil pan, get stretched to a prescibed amount. If too much torque is used, they are stretched that much more. Replacing the bolt alone won't do much so you are better to just keep it. I'd suggest you loosen the bolt a bit and re-torque with a functioning wrench. If it is torqued too tight, the engine vibration may play havoc with the threads. Best not to leave it as is. When you back off the bolt, do it with the good torque wrench and just take note of what torque it takes to move it. It won't be that accurate as you are going in the opposite direction but it will give you some idea of what it had.
For low torque applications, I prefer to use a torque wrench that has a needle. At least with these, you can see the torque building up and it doesn't matter if the needle goes "off zero" at rest after a while, you still see it move the required increment. With this type, you can see over time, when you need to replace it.
For common bolts like oil drain bolts that are encountered more often than any other bolt, I would suggest you get used to your own "mechanics" feel. Once that gets familiar to you, you can do these sorts of jobs with more confidence, with or without a torque wrench.

schwett

thanks for the advice xviper. the irony is that a) the only torque wrench i own is a beam type, and b) for things like oil changes i have almost never used one. it's not too hard to judge relatively low amounts of torque.

i'm worried that the pan is partially stripped from the last half turn or so, which is why i didn't take it out in the first place. it seems like it's made a good seal, but i certainly don't want it to vibrate a crack into the oil pan while i'm driving (fast.)

xviper

Depending on how much it was overtorqued, the crush washer may have saved your bacon - hard to say for sure at this point.

E30M3

Oil Drain Bolts are NOT structural or subject to fatigue or whatever. They just need to be tight enough not to leak or come loose. Leak tightness is mostly handled by the soft crush washer. Drain bolt tightening is easy to do by feel. Adequate tightening is way less than the bolt or threads can handle. Breaking something means you went way too far.

Quickie oil change places are reknowned for overtightening. Some old American cars with steel pans using welded in steel bushings are pretty forgiving as far as overtorquing goes compared to aluminum alloy pans.

I always tighten them by hand. If you insist on using a torque wrench, then use one that can accurately handle the rating. Which may require a smaller torque wrench than most folks have and use.

Stan

Destiny2002

I think the oil pan uses a hard steel insert to handle the oil bolt, correct me if I'm wrong. Therefore, it's possible that there was no damage.

If you find you have weak threads, consider installing a www.fumotovalve.com to replace to stripped bolt. They require less torque to install than a bolt and crush washer. You can also use a non-silicone liquid gasket on the threads as additional insurance against leaks at low installation torque.

pfb

Sorry to hear about the misfortune.

Long 3/8" and 1/2" torque wrenches have absolutely no business being anywhere near low torque fasteners like oil pan bolts.

Use a box wrench, snug it, then give it a little more. Done.

I've *never* seen any shop use a torque wrench on an oil pan!

Destiny2002

What's more important than having a torque wrench?

Having a CALIBRATED torque wrench!

Road Rage

I agree about the "feel" thing, and Honda's torque specs for these various bolts in the lube systems seem a bit high to me anyway. I find that you can feel when the crush washer gives - it feels like the steady pull you are exerting suddenly accelerates a bit - then I stop immediately. Better to have to re-tighten it a tad if you see some weeping, then go through the nightmare of a broken bolt or stripped pan. And i agree with Xviper 100% that a beam type of good quality will serve the home mechanic well - the pros need the speed of a precision click-type, especially if they are torqueing cylinder heads and such. Plus, in certain positions, it can be hard to read a beamer, whereas the clicker is a "blind" device. I was fortunate enough to have bought a some reasonably priced Asian-sourced clickers from IMPARTS many years ago, and when i compare them to my pal's mucho $$ Snap-On electronic, it is right in the ballpark.