How to Properly Use Anti-Seize

[jcslocum]

Anti-seize is not just for 2 different metals to avoid corrosion/galvanic effects. It's used on nearly all fasteners where a torque value is needed. Bolts should be cleaned and the paste reapplied to the THREADS and UNDER the HEAD of the bolt or the bearing surfaces of the nut. There is actually more friction under the bolt-head/nut than in the threads; 55% to 45%.

Most bolting is a +/- 10% of indicated torque. So 50 Ft. lbs gives you a 45 to 55 window. This typically induces a load of 50% of the yield strength of the fastener.

When torquing, even with a really good torque wrench that has been calibrated, you can still get a 25% scatter of load on the bolts. This has to do with the friction in the fasteners which is impossible to predict. Engineers take all of this into account when they design the joint and fasteners to make it all work.

There is much written on the subject and you can go blind reading it all. Lots of it contradictory.

Once a fastener is properly torqued, it should never come loose. The clamp load applied is calculated to be above the loads the joint will see in service usually by about a 2:1 safety factor.

[lkchris]

Contradictory for sure, although imho the best advice is follow the design engineers' specification. Those at the "mechanic" level don't have the background to decide different.

Mercedes goes out of its way to warn against using anti seize on wheel bolts. Porsche specifies using it.

Bosch spark plugs forbid using it.

For the original poster ... exhaust system connections downstream from those at the cylinder head are not particularly critical, and antiseize is likely a good idea in any event. Optimoly TA is probably better than the dime store (FLAPS) stuff.

[Burg Boxster]

Originally Posted by lkchris

Bosch spark plugs forbid using it.

The last few Bosch O2 sensors I bought had a dab on them...

[JFP in PA]

Originally Posted by lkchris

Bosch spark plugs forbid using it.

Good, you can have them come help you when their plugs pull the threads out of your aluminum heads...............

[stephen wilson]

Originally Posted by jakeru

Below shows after anti-seize "top-up":


This is the look I go for, in general, when I anti-seize a bolt or screw - not too heavy, evenly distributed on the threads.

Porsche also wants some Optimoly between the bolt head and spherical seat, but not on the cone portion.

[Flavor 987S]

I use a very small dab on the wheel hubs mating surface, so they come off easily, when doing winter hibernation cleaning prep.

[Cbonilla]

My 2003 986S manual specifically states to not put antiseize on the mating surfaces of the lug bolts. Rather, it calls for antiseize to be applied to the threads and the area in between the collar and the head (the area that's exposed when you try to separate the floating section from the bolt head)

[Burg Boxster]

Originally Posted by Flavor 987S

I use a very small dab on the wheel hubs mating surface...

Originally Posted by Cbonilla

My 2003 986S manual specifically states to not put antiseize on the mating surfaces of the lug bolts...

CB - Flav is NOT referring to wheel bolts but instead to back side of wheel which mates to rotor hat surface... which then mates to hub (where a/s should also be applied).

[Flavor 987S]

Originally Posted by Burg Boxster

CB - Flav is NOT referring to wheel bolts but instead to back side of wheel which mates to rotor hat surface... which then mates to hub (where a/s should also be applied).

Correct...

[Cbonilla]

Sorry, i mis-read, my mistake. For the record I also apply anti-seize to these surfaces, as well as where the hub-centric mounts on the wheel hubs meet the wheels themselves

[linderpat]

Folks - here is what I've found to be the definitive thread on antiseize. It's from Rennlist, 928 forum, but applicable here as well. Linky: https://rennlist.com/forums/928-forum/592090-experts-please-school-us-on-sealants-threadlockers-anti-seizes-and-lubricants.html

[JFP in PA]

Originally Posted by linderpat

Folks - here is what I've found to be the definitive thread on antiseize. It's from Rennlist, 928 forum, but applicable here as well. Linky: https://rennlist.com/forums/928-forum/592090-experts-please-school-us-on-sealants-threadlockers-anti-seizes-and-lubricants.html

And which contains some "old wife's tales" about the use of antiseize and thread lubricants. The use of either actually improves torque accuracy, it does not negatively effect anything, and will not cause properly torqued fasteners to come loose.