dr bob

The 'calibration' in my seasoned mechanic's hands has drifted some over the years. Depending on time of day and whether I ate or smoked my wheaties tha morning, the settings can be all over the map. For the most part I use the torque wrench these days, particularly on fasteners going into aluminum. Plus, since I have the tools to do it right, why not just do it right?

I've had the joy of disassembling things where the bolts into the aluminum have been torqued by feel, usually just to the point where the installer felt some yield in the threads. On disassembly, the aluminum threads that started to yield on installation continued to yield on removal. Think water pump bolts, and engine mount bolts, alternator and other accessory bolts that connect stuff to the engine block or gearbox. Think S3+ cam cover bolts, especially the two-piece bolts. Got a little seepage? Just tighten those a little to stop the leak, and end up with pulled threads and broken bolts. Would a torque wrench have saved them? Sure, if it was used every time a wrench touched those bolts.

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This thread is a tangent from a separate discussion at the time about the block drains. I could go search it down and get the exact wording, but in effect I had suggested that I am using Teflon thread sealant on the drain bolts, even though they are not the tapered 'pipe' threads that normally get sealant. I put a similar film of the thread sealant on the faces of the sealing washer so it doesn't gall as you tighten. Then torque wrench to just draw it up snug enough to seal and not fall out. For me that number is 15-16 lbs/ft, the same number one would use with a 8mm thread into aluminum. Corresponds nicely with the 13mm hex head on the drain bolt, common on 8mm bolts although this one is bigger. And with Dave's 19 lbs/ft recommendation, considering the sealing paste as a thread lubricant.

I do the same sealant thing on the oil drain plugs, by the way. I'd have to dig through notes to remember the oil drain plug torque I use though. It isn't much.

Rob Edwards

The only shop around here that doesn't use a torque wrench on pretty much everything is 928Intl.

GlenL

I'm not seasoned enough. I find doing things by hand to be especially variable when working in awkward positions or with the "wrong" wrench. I'll also reference the torque specs to see if large bolts only need small torques. The bolts holding the suspension to the body come to mind.

Those drain plugs get a light touch as I've stripped them while removing them! The threads are expected to be corroded and soft.

worf928

A number of folks have posted, more eloquently and succinctly, some of the thoughts in my head on this topic. One thing not mentioned:

We - as a community - encourage folks to work on their own 928s for reasons we all know and discuss. Each of us prioritizes these reasons in our own way. As a result of this encouragement we have a lot of folks that are turning the wrench on their own car for the first time ever or turning a wrench on a 928 for the first time, or attempting more challenging wrench turning than they have done before, etc.

n00bs in one way or another with no offense intended by use of the term.

I think that, for a n00b, relying on a torque spec for a fastener is far, far better than attempting to calibrate their arm based on reading internet posts.

Last, a little more of my personal experience from my n00b days:

On my '91, prior to that day on which I came close to over-crushing a block drain plug, I had become keenly sensitized to the issue of properly torquing fasteners in general and drain plugs in particular. Previously I had gone about the business of changing the gear oil in the transaxle.

I, of course, made the mistake of removing the drain plugs first. I then discovered that the fill plug was over-torqued. Using the logic of a longer cheater is always better I eventually rounded out the hex in the plug.

The transaxle drain plugs are a paragon of why the torque spec should be given some thought. It seems ridiculously low to your arm. I experienced this that's gotta-be-wrong 'arm feeling' again last weekend when I torqued the plugs on a 5-speed box. I was almost-shocked when the torque wrench beeped.

It is super easy to over-torque them with *anything* that has a 10mm hex-head on the end. I'm pretty sure I could over-torque them with the short-end of a normal 10mm Allen wrench.

Daniel5691

Worf:

Thanks. I am definitely a n00b to the 928, and fluid-filled things made of 30-year-old aluminum in general. And that's the true coolness of this forum; you guys have usually been down the path several times before. The time you spend giving advice and insight is very greatly appreciated. I mean that to you all. I would sell my 928 without this forum. The beast is too daunting and I am too goofophilic.

Dan

Ladybug83

^^^exactly my thought too.
Cant thank everyone enough

The Deputy

Whenever possible...try to use a six point shocket or wrench when removing drain plugs...especially the first time around. I find that the initial-removal of drain plug is always the most difficult, since normally, nothing is applied to the threads of the plug upon installation at the factory.

Funny story about torque...

I've been a fleet mechanic for the last twenty years, where each mechanic has his own portion of the fleet to maintain. So, one day a wheel comes loose on a vehicle...not one of my vehicles. Then a few months later another...not one of mine. Then another...not one of mine.

So, the boss goes out and buys a torque wrench designed for the job. We crank it up to specs, 550 foot pounds...and head out into the yard to torque lug nuts. Out of the 1200 lug nuts I torqued on my vehicles...I had one that turned a quarter turn. The two mechanics that had the loose wheel issues and started the need for this extra procedure made several turns on several lug nuts...if not all of them.

That is why I mentioned the "worth a grain of salt" to my earlier post.

And believe me...if you feel better using a torque wrench...by all means use one. However, please understand that these torque values apply to like new conditions...and also understand that whenever you are using an extension on your torque wrench the torque value changes in prespective to the length of the extension. And you are somewhat assuming that the original installation was not bugger-up in any way...or machining. If I had a dollar for every bolt or nut I ever removed, from its original position, that was buggered up...I'd be driving a new Porsche...instead of this thirty year old one. Okay...that's a lie...I love this thirty year old beast.

I guess the old adage..."All's well that ends well"... definitely applies to these situations...because I have seen things torqued properly that failed or held, and things that weren't hold or fail.

Brian.

bureau13

Hang on a sec...doesn't a torque wrench (at least the kind I have) break loose at a specified torque? If I put an extension on the handle, yes, it amplifies the torque I can apply, but it should still break loose at the same point. Right? Or am I confused about how these things work?

SwedeInSiam

How many calibrate their torque wrenches frequently? You supposed to. On ships I work on (tankers) we have to do it annually and get a certificate.

GlenL

It gets messed up if you put the extension on the business end of the wrench. For example, a crows foot.

IA friend made a long bar adaptor to create the hundreds of ft-lbs of torque for axle nuts using a 150 ft-lb wrench. He calculated the table for what was needed at the wrench to get the right torque on the nut. Cheaper than getting that 3/4" 500ft-lb torque wrench for some once-a-decade nuts.

I never cal. I should. I've connected up two wrenches and seen if they're close. Harbor Freight has a fairly cheap electronic torque sensor and I've thought about getting that.

dr bob

re: Calibrating torque wrenches

For many years, when I had tools in my hands, I survived with a coupl good Snap-On click-type torque wrenches. I had them calibrated after a couple years of regular use, but that included releasing the spring tension before putting them away each day, and NEVER dropping them. Calibration costs about 20% of the wrenches' replacement costs, and the guy would do them on the truck in a few minutes. Deadweight with a lever back in those days. Never more than 2.5% error. Those wrenches cost $80-125 each in the late 1960's, when a dollar was slightly more precious. They were like gold at the time.

Fast-forward to the modern days, when you can find similar clicker torque wrenches at Harbor Freight for about $10 each when they are on sale. I did a little comparison between the H-F wrenches and the similar Snap-On's, and they are within a hair of each other. Since we started hosting guest-owner clinics, I was thinking that using/dropping/losing the lower-cost wouldn't be as painful as one of the Snap-On antique pieces.

Bottom line is that there's really no excuse for not having and using at least a cheap set of torque wrenches in the box. Yes, there are fancy digital wrenches that beep and buzz to let you know when you are getting close to target torque. There are specialty wrenches that include torque plus an angle gauge on it for 'stretchy' one-use head bolts. But the basic 3/8" and 1/2" wrenches are fine for most things. The 1/4"-drive inch-pound wrench gets a lot of workout time for 8mm and smaller fasteners (thread size....) since even the 3/8"-drive turndown is too great at the bottom end of its range.

You'll be a lot happier with a little care doing car projects the right way with the right tools. Factor in the right lubricants, sealers and such, and you may find yourself taking a little pride and comfort from the work you do.

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Grab a copy of Rob Edwards' 928 torque values spreadsheet. It's hosted someplace that Rob will share. Although not complete-complete, it has most of the normally-needed values listed conveniently by system on the cars. I keep a copy handy on my 'garage' tablet/computer. Thanks Rob!

worf928

Note that if the crow foot wrench is at 90 degrees there is zero error. It's a IIRC cosine thing, so within 80-100 degrees of the business end of the wrench the error is calculable but negligible and in any case, arguably, better than not using a torque wrench if your arm-integrated torque wrench isn't calibrated.

The snap-on web site has directions on how to correct for gravity if you want to geek-out on this.

Ad0911

Darn, I just (today) bought a 2- 24 Nm torquewrench for the oil pan bolts. It was only EUR 25 but now can't use it anymore

Fogey1

Can't let this one get away without posting these two threads with great PIX.

https://rennlist.com/forums/928-foru...ieve-this.html
I'm f*cked - You're not going to believe this

https://rennlist.com/forums/928-foru...need-help.html
If it's not one thing it's another, need help!!!

Thanks for the PSA, Worf.

daveo90s4

The theads in the block are deeper than the plug is long. If the block threads are ruined simply use a longer (but not too long) bolt as a replacement plug. And do up hand tight 'firm'

Dave