FSM Torque Values & Broken Bolts

mtgstuber · **Joined:** Tue Sep 13, 2011 4:15 pm **Posts:** 66

Hi All,
I'm in the final stages of putting my CRD back together. I've run into two issues today and I'm wondering if anyone else has had the same. The fine service manual says that I should torque the bolts to the cooling fan support block to the engine block 149 Nm. I tried that. One of the bolts failed. Are these one-time-use-only bolts like the ones that hold the head on? Is this a misprint? Right now I've got the other three bolts at 100 Nm. I don't feel comfortable trying to take the others to 149 Nm. One of the others already feels a little soft. I'm wondering if that's good enough. Luckily I was able to back the broken bolt out. It simply stretched and deformed the thread, rather than snapping off and leaving a chunk in the engine block.
I have a similar issue with the crank shaft timing access caps. The fine service manual says 24.5 Nm. This seems like a pretty reasonable value. I set my torque wrench and started tightening, and then I felt the soft give of stripped threads. Argh! :furious:

I don't even want to think about taking a drill and a tap near it, only to get filings into the engine top end I've just finished rebuilding. Simultaneously, I can't leave them loose. One trip down my dirt road and they'll be out, leaving the engine open to lots of fine grit. I'm tempted to slather then with some JB Weld and pray that I can get them out again in 100k miles when I have to change the timing belt. (Assuming the blasted thing doesn't die on me again.)
It has not been a good evening with the CRD. Any suggestions?

DOC4444 · **Posted:** Wed Jun 05, 2013 6:06 am

Those numbers are obviously wildly wrong. You need to learn about threaded fastenrs in various materials. Best way is with an experienced mechanic who can demonstrate the "feel" you need to acquire before you do even more serious damage. And, for god's sake, do NOT put the cam plugs in with JB WELD! You need to learn about pipe thread. Tightening to a few inch pounds is plenty.

DOC

dirtmover · **Posted:** Wed Jun 05, 2013 8:10 am

Yeah, this issue has been highlighted before:

viewtopic.php?f=5&t=65759&view=next

You've probably compromised all the bolts so it's probably wise to replace them all.

In the case of the timing caps another member reported a few months ago finding one of them glued in place either by the PO or dealer during a previous service or maybe even at the factory, who knows? Rest assured you're not the first to face this problem.

As Doc points out you really need to get a feel for what's right for different sized fasteners and different materials rather than just blindly believing the "spec". Also bear in mind that torque specs are almost exclusively given for dry fasteners i.e. no contamination, lube, anti-sieze etc.

mtgstuber · **Joined:** Tue Sep 13, 2011 4:15 pm **Posts:** 66

Generally I do do things by feel and have never had a problem. Given how finicky this blasted machine has been I decided to do things to spec. Silly me.

Any constructive suggestions on the caps?

DOC4444 · **Posted:** Wed Jun 05, 2013 6:33 pm

There is nothing "finicky" about the hardware on a CRD.

DOC

mtgstuber · **Joined:** Tue Sep 13, 2011 4:15 pm **Posts:** 66

In my book an engine that needs so many modifications to be reliable is finicky. I guess we disagree.

If anyone has some specific ideas on the best way to move forward with respect to the caps, I really could use some good advice. Thank you all!

DOC4444 · **Posted:** Wed Jun 05, 2013 11:42 pm

"Hardware" = Threaded Fasteners

mtgstuber · **Joined:** Tue Sep 13, 2011 4:15 pm **Posts:** 66

I determined a partial solution, should anyone else run into a similar problem. Given the number of folks doing rocker jobs, I figure I may not be the only one . . .

VM Motori was nice enough to thread the entire shaft, which is substantially longer than access cap that comes with the engine. (I'm wondering if the error in the FSM regarding the torque is because they changed the length of the screw at some point. I think the torque specified might have been fine on longer screw.) The screw is 10mm x 1.0 TPMM. A screw that is approximately 10-12 mm will get past the damaged threads, while still not protruding through the inside of the housing, or coming anywhere close to the camshaft. Unfortunately my local hardware emporiums -- or at least the ones that were still open after work -- didn't have anything sufficiently short, however I was able to trim a longer one down and chase the threads with a die. My new plug has a slightly larger profile than the old one, which put it a little close to the heater lines on the exhaust side, but it looks like it's going to do the trick.

dirtmover, you made an observation that lubrication, antisieze, etc. impacted torque values. Any notion how torque specs should be adjusted when using lubrication or antisieze compound on the threads? I'm guessing you'd reduce the torque, but I'm curious if there is any rule of thumb about how much?

FSM Torque Values & Broken Bolts

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