First time user of a torque wrench

[senn]

ok real n00b question. The instructions are fairly vague (they assume u have some mechanical experience, silly things)

once you've done your 3 passes on the head bolts, it says something about going 90 degrees a couple times. So do i leave the wrench at the last setting (4A-GE 60nm) and just turn the bolts 90 deg each, twice? what's the reason behind that?

[jondee86]

Two completely different head bolt tightening techniques. With the torque wrench you make several
passes, increasing the wrench setting each time, until the final pass is at the specified torque. If you
use the 90 degree method, you snug the bolts down to some minimal starting torque, and then make
two passes with a power bar, turning the bolt 90 degrees at each pass.

You can use either method, BUT NOT BOTH !!!!!

Cheers... jondee86

EDIT: OK... doesn't have to be a power bar. You could set your torque wrench to a way high setting,
and then just use it like a power bar. The point is, you are tightening the bolt to a specified angle of
rotation, rather than a specified torque.

[senn]

so doing 3x passes (24nm, 40nm and final 60nm) is fine, i don't need to do any more with the head bolts?

[ca5pa]

so doing 3x passes (24nm, 40nm and final 60nm) is fine, i don't need to do any more with the head bolts?

To my knowledge. Drive the car once running for a short period of time. Then check the tensions again. Always good practice imo.

[Billzilla]

The other important things to do when using a torque wrench are to turn it slowly & smoothly or you won't get the correct torque, and to properly oil the bolt that you're tightening-up. The thread has to be lubricated but more important is to lubricate under the head of the bolt as well. Without doing that you can get a much lower torque on the bolt.

[senn]

thanks guys +rep for you all.

[Flex]

Good info guys, also which type of torque wrenches are the best? Click type or deflecting beam? Which brands are people using?

[senn]

i've heard "warren and brown" bandied about, but they were a bit pricey for my limited use. I have a CSL click type and (i'm sure this will scare some people) an "eclatorq" electronic one for low torque settings (10-100nm or so)

[jondee86]

...and to properly oil the bolt that you're tightening-up. The thread has to be lubricated but more important is to lubricate under the head of the bolt as well. Without doing that you can get a much lower torque on the bolt.

This seems to be one of the best kept secrets of the automotive world !! I have read the
Toyota Repair Manual from cover to cover, and nowhere does it specify if threads should
be oiled or not. And given the BIG difference in clamping force between oiled and dry
torqued bolts, I would have expected it to be spelled out in BIG LETTERS.

As you mention, under the head is probably even more important.

So, is it possible to say that ALL tightening torques listed by Toyota are for oiled bolts ?

Cheers... jondee86

[jimmmayyy]

I think you'll find it is more like just assumed knowledge.

[senn]

as the hayes manual says in the preface (not word for word) "this manual assumes you have some level of mechanical knowledge"

They aren't really writing for joe blow off the street...like me. None of these manuals are.

[eeeyan]

Dont go "back and forth" with a torque wrench either it should be one fluid motion "click" then relase for each tension level.

[Billzilla]

Some more stuff I remembered - When you're not using a torque wrench make sure to set it back to zero. Not so important for the beam-type, like the Warren & Brown, but it is for the click type.
Also never use them in the reverse direction, unless they're designed for it.
From memory there can be something like a 30% difference in clamping pressure between an unlubricated bolt and a loobed one.

[banana_socks]

Couple of things I learnt when studying fasteners.
-There can be a major difference between lubricated and dry bolts (as Billzilla said). Without lubrication a large part of the torque is overcoming thread friction and not actually tensioning the bolt.

-There is a big variation (up to 20%) in the tension of bolts using a torque wrench. This is because the torque you apply doesn't relate to the bolt tension identically for every bolt. Don't worry too much about them all being perfect, it's a rough guess at best.

-The biggest load a bolt ever sees is when it's being tightened. If you accidentally overtighten something, so long as it's not broken it should be fine. IIRC some of the head bolts are actually meant to be yielded.
(This is not true for head studs, which is their advantage)

[thechuckster]

Two completely different head bolt tightening techniques. With the torque wrench you make several
passes, increasing the wrench setting each time, until the final pass is at the specified torque. If you
use the 90 degree method, you snug the bolts down to some minimal starting torque, and then make
two passes with a power bar, turning the bolt 90 degrees at each pass.

You can use either method, BUT NOT BOTH !!!!!

this is wrong. way wrong.

torque-to-yield (TTY) bolts are designed to be tightened to a specific torque setting - then rotated a specific amount.

to ensure a consistent load on the head, block and the bolt's threads you tighten in stages. The further 90 degree twist then applies a fairly predictable amount of stretch on the bolts.

The reason the bolts are deemed one-use is that the first use has that stretch applied within the bolt or stud's designed plastic region (edited for correct term - thanks stu!). If you re-use the bolts, the added stretching can result in the bolts having a strain outside that design region and instead of assisting with clamping pressure you weaken the bolt and it either stretches more than designed or fails/breaks.