red loctite on case through bolts...should i or shouldn't i?

[Baby]

Yesterday I sealed up my case, and aside from the usual cold sweats and second guessing about the amount of sealant I used and wondering if I got all the mating surfaces, I'm optimistic. Tonight I need to go back and add the o-rings to the case through bolts.

Should I put red/blue loctite on the threads? (I did use a little red on the perimeter bolts, though I don't recall reading anywhere that I should.)

[Eagledriver]

I wouldn't do that. I don't know of anyone who does. Never heard of one of these coming loose. What reaction might the o-rings have to the locktite? Will the next rebuilder hate you for doing it?

-Andy

[Baby]

Thank you, Andy. I've never heard of it either, but I guess I'm surprised that the bolts would be torqued dry.

[MBruns]

I would not use loctite at all, I use a makeup oil (STP or Lucas) to lube the "O" rings as well as the acorn nuts on the thru bolts, they will torque up nicely.
Mike Bruns

[KTL]

I too put a little engine oil on the threads and the bearing surface of the captive washers. The nuts can squeak at you a bit if you don't. I don't think that's a good sign of being able to get consistent torque on each and every of those thru bolts, so I lube them up to eliminate the squeak.

No need to put any loctite on the perimeter nuts either. They are all lock nuts anyway, be they nyloc nuts or deformed thread nuts, so they are already resisting loosening.

[Baby]

Oil it is! Thanks for your help.

[Cupcar]

My bet is that Porsche speced the torques dry, they are pretty good at mentioning lubrication in the FSM when important.

Adding lubricant changes the theoretical torque spec.

[KTL]

Originally Posted by Cupcar

Adding lubricant changes the theoretical torque spec.

Agreed. But when you hear squeaking and, and sometimes have washer rotation that in turn wrecks the o-ring, you aren't getting consistent torque anyway. My thinking is some oil replicates the plating that allowed some reduced friction. Older nuts & washers where the plating has gotten corroded causes extra friction btwn the bottom of the nut and the nut contact surface on the washer.

[Cupcar]

I use WD-40 on bolts.

I then install the through bolts without the seals, torque and then remove the bolts one by one, insert seal and do a final torque.

This minimizes turning the seals as the case is drawn together and WD gives a bit of lube but not too much.

Also I use Dow 111 on seals, not much just coat the seal.

[Baby]

Curious, what is the difference, more or less, between dry and wet in terms of NM or ft-lbs for this application? Is a dry torque of 25 ft-lbs similar to a wet torque of ---just throwing out a number---30 ft-pounds?

[KTL]

It's actually dependent on what type of wet lube you use. Some thread locking compounds actually increase the friction more than a dry installation. So to get the amount of preload you would normally want dry, you would have to torque the bolt MORE.

I read an anti-seize rule of thumb is the torque needed to achieve the same clamping force is 2/3 to 3/4 that of the dry bolt. A 100 ft-lb torque specification becomes 70 ft-lbs with anti-seize! Also found that coating the head seating area of a fastener with lubricant could double the design preload or more.

Thankfully there seems to be a considerable amount of heavy duty fasteners on the Porsches so overtorquing them doesn't usually end up breaking the fasteners. Not saying I condone overtightening things. Just saying that most Porsche fastenings are pretty strong, so a bit of unintended over-torquing doesn't make the connection fail.

[Cupcar]

This is why torque angle or better yet measurement of bolt stretch is the way really critical fasteners are torqued.

[Baby]

2/3 to 3/4, damn! WD-40, oil, copper anti-seize...seems like people use all kinds of lubes.