Oil pump case nut torque?

[swade]

I searched this and the tech forum and the various manuals I have. What is the torque value for the 4 rib aluminum oil pump case nuts? Thanks for the help.

W

[Walt Fricke]

Wade

If ever there was a fastener whose torque is not critical, this has to be it. The O rings hold the pump in place, and the plates whose edges you fold will keep the nut from turning. I just do it with a regular handled socket wrench, and don't check torque.

But 18 lbs/ft should do it. That is a standard torque for 8mm fasteners where crush washers are not used. Same as what you will use for all the case perimiter nuts, the chain box nuts, the cam carrier nuts, and a whole variety of other nuts on 8mm studs.

[swade]

Thanks Walt, appreciate the reply.

W

[ajwans]

Some guys are using prevailing torque lock nuts rather than those dinky
little folding washers.

andy

[917guy]

I have done research on these things for transformer oil submersion. We found that nylon hardware (5/8"UNC bolts) components were failing. In a $3 million unit, that costs over a million in sales if it breaks, this can be a big deal. Some formulations of nylon include plasticizers that leach out under hot oil. When this happens, the nylon gets smaller. In the case of nuts with a little captive ring of nylon, they lose quite a bit of their original torque, i.e. are easier to remove after hot immersion. There are plastic resins that are unaffected by hot oil. We prefer those resins for our transformer hardware. If nuts are made for hot oil, they will be fine.

How to test unknown nuts:

Fasten a nut and bolt, with the nut mid way along the treads. Place in a soup can half filled with the subject oil. Cover with foil. Put in a 100C oven for 4 weeks. Remove, put the bolt head in a vice. Use a needle type beam torque wrench to remove the nut. Not a click type. Record the needle readings as the nut begins to turn. Compare with a bolt / nut that was not baked or immersed. If you are anywhere close, those nuts are "OK". Bent tabs can be home made, and are reliable, as is threadlocker.

[Walt Fricke]

I have gotten the impression that "prevailing torque" nuts mean ones with distorted threads or the like, not the Nyloc type. I'm not sure why that name was chosen.

I may have to wait a while to get exclusive use of my oven for 4 weeks, though, before performing such a test.

Threadlockers are heat sensitive, but I suppose ought not to see more than 300 degrees F?

Me, I reuse the tabs. No problemo, though I have a few new ones in my stash if I remember to look for them.

[KTL]

I thought the question was, what is the torque spec for the small nuts on the oil pump itself, not the M8 nuts that fasten the pump into the case.........

I agree the pump lock tabs are unnecessary. An ordinary all-metal lock nut would do just fine.

[turbo nut]

I was told a long time ago. The reason the locking tabs were used was because you don't want the pump very tight. I was told to just snug the nuts down and bend the tabs. He said this helps the pump sort of self align with the intermediate shaft and drive coupler. Prevents burnt up shafts on the pumps. Thats what we have done for years with no issues.

[KTL]

I think alot of people that are torque spec faithfuls have been torquing the pump to 18 ft-lbs religiously for years? I've never heard about the shaft binding issue until recently. Funny you mention the burnt up shaft issue because I was just talking about that this past weekend with a Porsche service tech I know. He said the same thing about the shaft alignment (needs to be able to "float" back & forth). I hadn't considered that the freedom of the shaft to move laterally is so important.

[Walt Fricke]

Well, if the oil pump is supposed to float, Porsche neglected to say anything about that in the Workshop Manual.

"7. Insert intermediate shaft with oil pump into right-hand crankcase half and tighten nuts.

Secure nuts with new tab washers."

One of the quirks of the Factory manuals is that they presuppose the reader is a trained mechanic. Which is why the listing of tightening torques in the manual for the engine gives only about eight to ten - rods, heads, through-bolts, case perimeter, flywheel, rocker shaft, crank pulley as I recall.

[KTL]

I just know the shaft is supposed to float. I don't know about the pump having some freedom to keep the shaft free. As long as that splined tube moves freely back and forth no matter what torque you put on the pump fastening nuts, I would say all is good.

Even though the engine case is closed up, the pump moving too much could be a bad thing? Let's say the nuts are just barely tight and lock-tabbed. If the pump can move back and forth a bit (due to applied load from I-shaft, then relax on power reduction) that could elongate the holes in the pump mountings?

Sure the shaft, case halves and fastening nuts are all fixing it in place. But there's some give in terms of the case's influence on fastening. The pump seals are soft enough to allow some movement there.

[swade]

For the pump case nuts I used 10 ft/lbs with some locktite, these are for the 6mm studs that come through the pump itself. The pump turned nice with no catching after torquing the nuts. I used 18 ft/lbs on the pump fastening prevaling torque nuts and used the lock tabs. I reached through the oil return tube holes this evening and made sure the splined shaft floats back and forth and it does. There was so much talk about this that i started getting a bit worried... I think I am OK.

Thanks again,

Wade