Torque Wet or Dry for Connecting Rod Bolts

[SaltyNC]

I have been reading the various DIYs on rod bearing replacement, and I know on the ARP bolts, they recommend using their lube on the threads and head before torquing. However, for OEM rod bolts, the official TIS mentions nothing about oiling the rod bolts or using assembly lube for the bolts.

My thinking is that BMW doesn't mention lubricating the rod bolts, because the rod threads are already wet with oil, so the bolt will be lubricated slightly with 10W60 as it is threaded, and their torque procedure accounts for this.

For our resident engineers and engine building experts, does that sound right? It looks on the surface like a dry torque, but it's actually a wet torque?

I know, I'm probably overthinking all this, but I want to make sure I do it right. Thanks all for your input and patience while I hash all this out.

Salty

[StickMon]

I would vote for wet.
Like you say, they're going to be oily already.
The amount of effort required to get them dry would be worth mentioning in the TIS if it were a requirement.

[The HACK]

OEM bolts are torque to yield (angle torqued multiple times)? They need to be dry IMO.

[ZAR4MC]

Originally Posted by The HACK

OEM bolts are torque to yield (angle torqued multiple times)? They need to be dry IMO.

agree with Hack, my new OEM bolts where also dry when torqued.

[steffenme1]

I know the BMW torque spec sheet says this.



To be fair I'm genuinely unsure if that document started life as an actual BMW document or if it's 100% home-grown. I know the TIS doesn't mention it either way.

[GuidoK]

Usually rodbolts and similar situations (inside the engine) are torqued wet.
For the s54 bmw has written this elaborate instruction for multiple torquing and maybe they forgot that.
For all other bmw eninges its wet.
Also its virtually impossible to do it dry, because you're not going to clean out the holes with a solvent and a cotton bud (and oil is still dripping inside that hole because you have to lube the crank and bearings). Thats why bolts inside the engine are usually torqued wet.

[SaltyNC]

Originally Posted by GuidoK

Also its virtually impossible to do it dry, because you're not going to clean out the holes with a solvent and a cotton bud (and oil is still dripping inside that hole because you have to lube the crank and bearings).

That's what I was thinking. They were so elaborate with the other instructions, and they specifically say to "moisten" the bearing shells with 10W60. If they had wanted the rod threads to be sprayed down with MAF cleaner or similar and wanted the threads wiped clean inside the rod, they would have said so. I think they assumed the procedure would be done with the residual oil on the rod threads, so there was no need to lube the bolt, because it was going in a wet hole (ahemmm).

Salty

[GuidoK]

If youre going to do the shells yourself, once you're done dont start the engine.
First remove the plugs, turn the crank manually with a ratchet, pull the fuel pump fuse and crank it until you have oil pressure.

[SaltyNC]

Originally Posted by GuidoK

If youre going to do the shells yourself, once you're done dont start the engine.
First remove the plugs, turn the crank manually with a ratchet, pull the fuel pump fuse and crank it until you have oil pressure.

Thanks for the advice, Guido. I appreciate it. Luckily, I did have that in my notes. There are some very thorough DIYs on the M3 forums, some here, videos on YouTube, hints and tips in forum follow-ups, etc. It's scattered about, but amazing how much information is available for us.

If I don't get in over my head on this, I'll document everything on the Z4M, and make up a thorough DIY for us.

Salty