View Full Version : Torque to yield bolts: Replace or Reuse

01-11-2014, 04:13 PM
2006 T1N, OM647, 3500, 158, SHC, cargo, single air, 150,042 miles
Getting ready to start reassembly of engine - after a burned piston engine failure. Just got the block, crank and head back from the machine shop. Kit includes new head bolts.

I have the manual, thanks to this forum. The torque specs (pages 9 - 11-16) list many torque to yield TTY bolts.
My previous experience tells me replace all TTY bolts, Is this necessary or recommended?

Head Bolts? 44ft-lb + 90deg + 90deg YES I am going to replace.
Injector hold down? YES I am going to replace.

Crankshaft -
Main Bearing Bolts? 40ft-lb + 90deg ? Necessary or Recommended?
Rod Bearing Bolts? 44in-lb + 221in-lb + 90deg? Necessary or Recommended?
Vib Damper Bolt (10.9)? 240ft-lb + 90deg? WOW! Necessary or Recommended?
Flywheel Bolts? 33ft-lb + 90deg? Necessary or Recommended?

Camshaft -
Exh. cam Sprocket bolts? 159in-lb, not TTY, but manual says "Do NOT reuse"? Replace?
Cam tower bolts (24 of them). 80in-lb. Not TTY, reuse?

Any others?

After reading many threads on the vibration damper, should I replace it? Mine is single pulley with no visible problem.

01-11-2014, 04:37 PM
replace, cheap insurance.

Aqua Puttana
01-11-2014, 04:47 PM
replace, cheap insurance.
Given the theory and design of TTY is there any other choice? :idunno:


01-11-2014, 04:54 PM
Thanks, that was my initial thought, especially with how much I am already spending, it seems fairly cheap insurance. Just another aggrevation with more parts to order and wait a few more days for.

01-11-2014, 07:18 PM
Advise---- Do NOT re-use the crankshaft/damper pulley bolt.
I have had three detach in service causing moderate damage to the crank nose.

12-07-2019, 09:27 PM
From what I see, the 2006 FSM does not specify reusing or replacing any of the bolts listed above, except:

Head Bolts: OK to reuse as long as they have not stretched beyond 104mm. It provides a permissible length of 102mm to 104mm.
Cam Gear Bolts: "Do not reuse" (It actually notes this in one section of the manual, but omits it in another -- not the only typo/contradiction in the manual I've seen. The dealership told me they do not have the usual "must replace" notice and advised based on their info I did not need to replace them **but I did anyway**)

As for the rest of the bolts listed above -- nothing mentioned at all, which would lead most to assume they are ok to reuse. As the responses here state, generally TTY bolts should not be reused though. This is another issue with the factory service manual, IMO, and surely could lead to issues for those following it closely and not second-guessing.

Last time I had my head off, I replaced my cam gear bolts and my head bolts (with aftermarkets through europarts-sd) because I had a head gasket issue and didn't want to risk it. My used head bolts measured just over 102mm but I tossed them. This time I have it apart, my head bolts again measure just over 102mm and I am considering reusing them since the manual advises this. I'm mid-convo with Dennis Linden so I'm curious to see his response to this but figured I'd share what I know on the subject.
If they list a stretch spec on these, why not the others? So many inconsistencies with this "reference material," sigh.

A little crazy and a little annoying to have so many TTY bolts on this motor, I have never worked on an engine with so much one-time-use hardware.

12-08-2019, 01:42 PM
In the WIS documents
Replace bolts to exhaust camshaft
Head bolts OK up to 104mm
Crankshaft bolts up to 63.8mm
Conrod bolts up to 48mm
Flywheel bolts replace
Vibration damper replace

12-08-2019, 02:26 PM
Well I simply replace all vital bolts including rod and crank cap fasteners.

For some reason cap # 2 is subjected to much higher stresses than the rest, and cap distortion is often detected at this point on rebuilds .

In some circumstances I have been forced to replace a cap and realign the crank tunnel to recover an otherwise good block.

Many years ago I re-used all good cap and rod bolts but after having a right side #2 securing bolt simply snap under crank stress in service and wreck an engine I undertook a policy of replacing them with new every time .


12-13-2019, 01:19 AM
thank you both for your input -- I have new replacement bolts now (which were quite hard to find).

The main bearing cap bolts are a 12 point -- but is it a special type of socket? A 12mm 12-point doesn't fit and a 13mm 12-point is a bit loose. Possibly a 1/2" 12-point? Or maybe a triple-square socket or something else a bit out of the ordinary? We removed the old bolts with a 13mm socket but it didn't feel great, trying to figure out if I need to grab something different to install the new ones this coming week.

12-13-2019, 01:51 AM
Use 1/2" A/F 12 point double depth socket with 1 /2 inch drive.
I use Snap On socket pt # S161A.

12-13-2019, 01:56 AM
Edit: dennis covered it : )

I don't have the real answer for you, but this image might help discussion
https://redirect.viglink.com/?format=go&jsonp=vglnk_157620207824014&key=8d1879ea4db6639656bbe1af129db4fc&libId=k43hzbvl010025g3000DAbwamkk0r&loc=https%3A%2F%2Fwww.garagejournal.com%2Fforum%2F showthread.php%3Ft%3D406007&v=1&out=http%3A%2F%2Fwww.cnctechnw.com%2Fpics%2FTriple Sq-vs-12Pt.jpg&ref=https%3A%2F%2Fwww.google.com%2F&title=XZN%20triple%20square%20vs%2012%20pt%20splin e%20vs%20double%20hex%20-%20The%20Garage%20Journal%20Board&txt=%3Cimg%20src%3D%22http%3A%2F%2Fwww.cnctechnw.c om%2Fpics%2FTripleSq-vs-12Pt.jpg%22%20style%3D%22max-width%3A%20675px%3B%20max-height%20%3A%201000px%3B%20%22%20border%3D%220%22% 20alt%3D%22%22%3E

Personally I would be ok using the 12 point 13mm that you removed the old ones with, unless there was clear damage or the socket was getting wedged/stuck on the bolts.

12-13-2019, 08:08 PM
Yes, the 13mm 12-point was getting wedged slightly on the bolt heads so definitely not an ideal route.
According to your photo these are not triple square, definitely more than a 90 degree angle on the points. Strange to use a standard size socket on one bolt only though, hmm.

Also wanted to note since it isn’t included in this thread: Dennis recommends elsewhere to replace the crank bolt washer along with the crank bolt. I didn’t know this until a couple days ago. Mine looks fine and only has 65k miles and they’re quite beefy but has me thinking just in case.