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MG TD TF 1500 - Fan bolt torque limit

Danged if I can find the number. I'm at that point in putting Lazarus back together. I'm not about to break another one (even with the radiator off). Can someone give me the value? Bud
Bud Krueger

I am not sure I have ever seen one Bud but I have always simply tightened them up to a point where the bolts felt snug and the lock washers are fully compressed. I guess the application of some lock tite would be a good idea too.
Jim Merz

Did it that way once, Jim. Went fine until the 4th one decided to give up the ghost. BTW, the fan that I'm putting on is the seven blade one that I got from you a while ago. Bud
Bud Krueger

Bud

This link should give you a steer in the right direction

http://www.cncexpo.com/MetricBoltTorque.aspx

The difficulty might be in identifying the grade of bolts in your possession. I personally would err on the side of caution and use the figures for the softest grade.

Graeme
G Evans

Thank you, Graeme. I would think that 5x.75 should be very close to 5x.80. Bud
Bud Krueger

Bud - Be very careful about using that torque chart as is is for high tensile strength which our bolts are not (The softest grade on that chart is 8.8 with a torque spec of 800Nm or 560 ftlb, which doesn't make any sense to me). Torquing to those specs will result in a bolt that will pull apart somewhere in the middle, leaving long pointy ends on each of the two parts. The camshaft thrust plate can be either 5 X 0.75mm or a 6 X 1.0 mm and I have that down as 6 LBFT of torque and even at that, I would work up to it very carefully and if it starts to feel like is turning and not tightening anymore, stop right there. LocTite, per Jim's would be a good thing (green or purple grade). Cheers - Dave
David DuBois

Dave, from the table a M5 x .8 shows a torque value of 54 in-lbs (4.5 ft-lbs.). I think you are looking at the tensile strength of the steel used in the grade 8.8 small bolts.
Cheers, Hugh
H.D. Pite

Hugh - "from the table a M5 x .8 shows a torque value of 54 in-lbs (4.5 ft-lbs.)"
You are correct - that's why my statement that the figures didn't make much to me. 4.5 ftlbs sounds much more reasonable. Thanks for the correction. Cheers - Dave

PS in my defense, I have been almost flat on my back most of the week, fighting off pneumonia.
David DuBois

Dave, one of the (now replaced) bolts showed that wasp-waist look. Think I'll settle on 40 in-lbs with some loctite as a lube. That'll be after today's blizzard with 50+ mph winds. Still better than the mudslides at your end, Dave. Bud
Bud Krueger

I think there are way too many variables for bolts like this to come up with an actual torque value. The bolts could be brittle, stretched, original, replacement, etc. The pulley threads could be rusted or tight, loose, etc. Maybe when all was brand new, but now I would just snug by hand, gripping the wrench close to the bolt. Make sure the lock washers are good, and you should be fine. BTW, using Loctite in the past, there have been times where it has really tightened up (ie started to work) well before a fastener was tightened. George
George Butz

This thread was discussed between 25/03/2014 and 26/03/2014

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