Why does the manual call for new oil pickup bolts?

[ThisGuy]

I get that pretty much no one actually does this, and a little threadlock does the trick. But why does the service manual call for replacing these every time the oil pickups are disassembled? They're just screws… “CAPSCREW, M6 X 12”… What can change in the single use of a screw that warrants (recommending) replacing them every time?

To be clear, part #11 here:

 

[Claviger]

Probably because they're a "critical failure" item if they allow the screens to move and let all that crap flow around the motor.

It's a steel bolt into aluminum though....

 

[barbagris]

It's a steel bolt into aluminum though....

Ah - A Helicoil'ing opportunity.

 

[Claviger]

I get that pretty much no one actually does this, and a little threadlock does the trick. But why does the service manual call for replacing these every time the oil pickups are disassembled? They're just screws… “CAPSCREW, M6 X 12”… What can change in the single use of a screw that warrants (recommending) replacing them every time?

To be clear, part #11 here:

You can do what I'm doing with a bunch of the bolts and put in predrilled bolts so you can wire them. Zero risk of failure that way and don't need to replace if it's not a "torque critical" bolt.

 

[barbagris]

You can do what I'm doing with a bunch of the bolts and put in predrilled bolts so you can wire them.

Titanium I hope, to offset the weight of that wire.!

 

[ThisGuy]

You can do what I'm doing with a bunch of the bolts and put in predrilled bolts so you can wire them. Zero risk of failure that way and don't need to replace if it's not a "torque critical" bolt.

I can tell the longer I hang out on this forum, the greater the extremes I'll end up going to. Having learned to safety wire in the navy (when I was briefly destined to be an aviation grunt), it's been tempting me…

 

[Claviger]

While it's not at all necessary, I just figure, while I'm in it why not do it better than factory?

 

[warp9.9]

Because they come pre coated with thread locker. They don't figure your smart enough to clean and apply medium strength thread locker yourself. :

 

[rash_powder]

Is it possible that upon removal oil gets on the threads and they figure it is easier to replace the wetted screws with new dry ones than it would be to replace them? Oil wetted threads may not stay tight the way dry threads would.

I know that sounds like a load of BS, and I feel dumb for posting it because there would be oil in the hole too. And oil seeps in any way. But ENGINEERS........

 

[ThisGuy]

Is it possible that upon removal oil gets on the threads and they figure it is easier to replace the wetted screws with new dry ones than it would be to replace them? Oil wetted threads may not stay tight the way dry threads would.

I know that sounds like a load of BS, and I feel dumb for posting it because there would be oil in the hole too. And oil seeps in any way. But ENGINEERS........

It’s an interesting thought. It definitely affects the torque. Question is, do they just account for that in the instructions? There’s nothing in the manual about cleaning thoroughly before reassembly, so they must assume it’s going to be oil covered.

I also haven’t seen the replacement bolts. If they come coated with thread locker as mentioned above, does that negate the oil in the threads when assembling, and secure with the same torque whether dry or oily? No idea on the engineering there.