Torque Setting for Water Pump Bolts with Anti-seize?

[emerydc8]

I am starting to get what sounds like a bad bearing on my water pump. In anticipation of replacing it, I was doing some research and I found this article at http://www.w124-zone.com/downloads/MB CD/W124/Index/MiscFiles/M119WaterpumpRemoval.pdf that says:

DO NOT OVER TIGHTEN esp. with anti-seize on bolts and into aluminum. Most bolts are 21 Nm, but with anti-seize on them, it's closer to 12-15 Nm. Do NOT use a 3/8-drive ratchet to put any bolts ON, only 1/4-drive with about a 5-inch long handle so I don't overly torque anything.

I never gave this much thought because I almost always use anti-seize on bolts unless they go into a water jacket, then I use Permatex high-temp thread sealant. Is there really that much disparity in torque when using anti-seize on the threads? This seems like a lot.

 

[gerryvz]

I never put much anti-seize on any bolt (very thin film) and I just use normal torque specs. That's just me though.


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[samiam44]

Just use blue locktite on the threads, except the ones which require sealant.

 

[emerydc8]

I never put much anti-seize on any bolt (very thin film) and I just use normal torque specs. That's just me though.

Thanks, Gerry. So you do use some (very thin film) anti-seize and still torque it to the factory spec. I don't cake it on either, but I was just curious about how it might affect the actual torque. I ran into a similar issue with head bolts on a small block Chevy I rebuilt this month and wondered how using the Permatex teflon would affect head bolt torque. The FSM says to use sealant and specifies the torque, but trying to get any consensus on the Camaro forum on this issue seems to be a lot like asking what's the best transmission fluid.

 

[gsxr]

Official word from fastener experts is that when anti-seize is applied to threads, the torque spec should be reduced by some amount, if the spec is for dry threads. How much depends on what website you read. I think the bolts were coated when assembled at the factory which was supposed to prevent seizure, so the factory method would probably be to use new bolts? (Klink?)

I generally prefer to use anti-seize on anything screwed into aluminum and reduce torque spec by maybe 10-30%, roughly. (Exceptions are bolts which require either threadlock, or sealant to prevent oil leaks - MB usually specs the orange anaerobic stuff on the threads for leak prevention.) I also like to torque in stages... i.e. initial torque to 5Nm in criss-cross pattern; then 10Nm, etc until you reach final torque. If possible, run a tap into each hole to carefully (!!) chase the threads; and at least wire brush the old bolts if not run them through a die to clean them up.

I've only done an M119 water pump once and I honestly cannot remember exactly what I did for torque spec... it was ~5 years ago.

 

[emerydc8]

Thanks, Dave. I'll plan to go on the light side for the torque, but I'm not quite ready to take it down to 60% of spec as the above notes suggest. Maybe we can get more feedback on this.

I've only done an M119 water pump once and I honestly cannot remember exactly what I did for torque spec... it was ~5 years ago.

I did a 119 water pump back in 2007, but it was on the 400E and I had to take the crank bolt out -- there was no way to walk the damper off. It turned out to be much more than I expected. At least it cleaned up well and while I was in there I replaced the main seal.

 

[Klink]

I just use a super thin coat and tighten to spec, maybe minus 20%-10%(?) adjusted for feel. There is a certain feel to a correctly tightened assembly. That just comes from experience...

 

[emerydc8]

Thanks, Klink. And thankfully for those of us who lack that kind of feel, we have torque wrenches. I'll plan to back off the water pump bolts by 2 or 3 nm. Thanks again.

 

[gerryvz]

I just use a super thin coat and tighten to spec, maybe minus 20%-10%(?) adjusted for feel. There is a certain feel to a correctly tightened assembly. That just comes from experience...

Agree.


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