QuestionQUESTION: 99 Chrysler LHS timing covers (part aluminum cast, and part stamped steel) use M9.8 bolts. What torque do I tighten them to? The manual I have lists: M6=105 in/lbs, M8=250 in/lbs, and M10=40 The last one (M10) must be an error?
ANSWER: Hi Richie,
That last M10 is 40 foot-pounds, which is about twice the torque for the M8, and about 4 times that of the M6. Sorry for the delay but I was in the middle of cooking dinner.
Please 'rate/nominate' this answer/me (See the PS below).
Thanks,
Roland
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QUESTION: Does 40 foot-pounds seem a bit excessive for what appears to be nothing more than a shield for the timing belt? I started tightening the retaining bolts around the perimeter, tighter each round, and when I got to about 120 in-pounds, one of the bolts stripped through the housing — so I'm thinking maybe the torque listed in the repair manual is an error? What is your opinion?
ANSWER: Hi Richie,
There are two different numerical aspects of a given type of bolt material (cast iron in the case of the timing cover bolts, I assume; not aluminum). The M stands for metric and the number that follows is the thread diameter (but that is not the number actually shown on the bolt head which is the strength of the bolt). So the numbers shown for the torque of the timing cover bolts is dependent upon there being a proper number for that strength as shown on the head of the bolt. For all three bolt sizes involved here the number would have to be 8 or higher or the bolt will not withstand the torque recommended.
Which diameter bolt stripped on you (I hope the threads of the block didn't strip)? I do agree with you that those recommended torques are too high for the purpose to which they are being put. The very same torque numbers were given in the 2004 manual. So I would be inclined to use my experience/judgment rather than go by the manual on these.
Roland
Please do a rate/nomination of me answer/me if you believe I merit that. Thanks
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QUESTION: It is strange that they even mention the 3 different torques, since none of them represent the actual bolts involved. I believe there are 13 in total, and they are all labeled M9.8 (as well as all being the same length). And yes, it was threads in the block. In my second attempt, I tried to use the lowest of the three values, but that seems excessive as well. If you have a suggestion as to what torque might be adequate for the job (as I have no idea), I would greatly appreciate your input. Otherwise, they'll get the old Smith "stop just before you twist their heads off" torque, that I learned from my father, and he from his father... (snicker, snicker).
P.S. I tried asking a few mechanics at the Chrysler dealership about it, but got no information of any use. I guess they were too busy...
AnswerHi Richie,
While you didn't tell me the thread diameter, let me give you the spec for a M10 that is 8 mm in diameter measured at the threads (which is 28 foot-pounds), while that for a 10 mm diameter thread is 58 foot-pounds. M9.8 is a bit weaker than M10 so 25 and 50 foot-pounds max torque for those two bolt sizes would be what I would stay below. So measure the diameter of the bolts at the threads and act accordingly. If by chance these are 6 mm bolt thread diameter then the max strength listed is for an M7 and the foot-pound limit is only 8 foot-pounds. Measure to determine which diameter you are working with and observe the limits I have given above. Let me know the bolt diameters of those 13 bolts.
Please 'rate/nominate' again if you would do that once more.
Thanks,
roland
