reusing oil pan bolts?

[Migizi]

Replacing the Oil Pan today and discovered at the last moment that I had ordered/recieved the wrong bolts that hold the oil pan in place.

the original ones I removed have a fat washer attached (non removable) and the replacements I had received do not have these fat washers - this makes the new bolts too long :headbang:

I know it is recommended to use new bolts when dealing the the N52 3.0si valve cover, but is this necessary for the oil pan since it has a rubber seal??

 

[lucasxdiniz]

I wouldn't re-use them.

https://www.newtis.info/tisv2/a/en/e86-z4-3.0si-cou/repair-manuals/11-engine/11-13-oil-sump/5YsRxdW

 

[Chris_D]

It's always best to use new bolts where indicated although it won't be a dealbreaker for the oilpan unless they're really stretched and out of spec. I replaced my sump gasket 3 years ago and re-used the same bolts and have never had an issue. Mine is the M54 tho so maybe different specs.

If you absolutely have to re-use them then try to use at least new washers, put a flattened cardboard box under the engine (if undertray is removed) and keep an eye out for leaks.
Replacing with new bolts later will obviously mean an oil change and a new gasket.

 

[lucasxdiniz]

It's always best to use new bolts where indicated although it won't be a dealbreaker for the oilpan unless they're really stretched and out of spec. I replaced my sump gasket 3 years ago and re-used the same bolts and have never had an issue. Mine is the M54 tho so maybe different specs.

If you absolutely have to re-use them then try to use at least new washers, put a flattened cardboard box under the engine (if undertray is removed) and keep an eye out for leaks.
Replacing with new bolts later will obviously mean an oil change and a new gasket.

I checked the technical manual for the M54 sump gasket replacement, nothing about replacing the bolts is mentioned

 

[Smartbear]

It's always best to use new bolts where indicated although it won't be a dealbreaker for the oilpan unless they're really stretched and out of spec. I replaced my sump gasket 3 years ago and re-used the same bolts and have never had an issue. Mine is the M54 tho so maybe different specs.

If you absolutely have to re-use them then try to use at least new washers, put a flattened cardboard box under the engine (if undertray is removed) and keep an eye out for leaks.
Replacing with new bolts later will obviously mean an oil change and a new gasket.

You should be able to change the bolts over for new ones individually without needing a replacement gasket or an oil change
Rob

 

[Mr Tidy]

I understood that anything attached to the engine block on the N52 engine was attached using single use aluminium bolts because it's a magnesium/aluminium block. Steel bolts don't expand and contract at the same rate when they heat/cool.

 

[Chris_D]

It's always best to use new bolts where indicated although it won't be a dealbreaker for the oilpan unless they're really stretched and out of spec. I replaced my sump gasket 3 years ago and re-used the same bolts and have never had an issue. Mine is the M54 tho so maybe different specs.

If you absolutely have to re-use them then try to use at least new washers, put a flattened cardboard box under the engine (if undertray is removed) and keep an eye out for leaks.
Replacing with new bolts later will obviously mean an oil change and a new gasket.

You should be able to change the bolts over for new ones individually without needing a replacement gasket or an oil change
Rob

Good point! I suppose you could still pattern-torque them that way too if you're careful to keep track of which bolts are going in and when.

 

[Migizi]

I figured as long as I was this far into the project I should just do it correctly, so I went to the dealer and coughed up $70US for a set of bolts vs ($35US on eBay).

Now I have another question - the TiS calls for 8nm torque / angle 90 degrees for the oil pan bolts
I don't have an angle torque, just a regular torque - how critical do you all think this particular torque setting is? after all, there is a rubber seal?

think 8nm torque (without the 90 degree method) will be ok?

 

[Chippie]

If 90 degrees is the angle turned after the 8nm torque then it’s only a quarter turn, it shouldn’t be too hard to get near enough.

 

[GuidoK]

If they're aluminium bolts: NEVER reuse!

think 8nm torque (without the 90 degree method) will be ok?

Always use the angle torque too in this case. It's purpose is probably to compress the gasket (so the 8Nm serves as 'bolts all being snug to the gasket to the same point' and the 90deg serves as the amount of compression on the gasket).
It's just a quarter turn. It's not the end of the world if its not exactly 90deg.

 

[Migizi]

I took the advice and finished the 90 degree angle torque :?

The entire process of replacing the oil pan gasket was fairly easy, just a little time consuming. Probably took a total of 5-6 hrs. dealer wanted over $1200us :rofl:

 

[Crazy Harry]

I took the advice and finished the 90 degree angle torque :?

The entire process of replacing the oil pan gasket was fairly easy, just a little time consuming. Probably took a total of 5-6 hrs. dealer wanted over $1200us :rofl:

Win, win $'s saved and look how much more you know now!

 

[GuidoK]

$1200us?
It's a 3 hour job for a trained mechanic with the proper BMW tools

 

[Liam22]

If they're aluminium bolts: NEVER reuse!

I'm interested in this. Holding the sump to block is a very low torque, low stress job for the bolt. 8Nm+90° is hardly going to stretch the bolt, and my understanding is that the lack of elasticity of aluminium is the determining factor for single use.

So for high torque applications like gearbox bell housing, and aux belt tensioner, then one time use seems sensible. For low torque like sump and maybe even water pump, then a few uses should be fine.

The problem is you can't tell how many times they've been used and so BMW will recommend single use in all cases.

Is there evidence for the contrary view?

 

[GuidoK]

8Nm plus 90deg isnt a low torque.
True, its an M8 bolt and on for example the m54 the m8 bolts need 22Nm (but without the torque angle!). (8Nm is more of a torque spec for M6 steel bolt)
Also, bear in mind that the 8.8 grade bolts on the m54 have a yield strenght of 90+ KSI / 630+MPA but 6061 T6 aluminium (one of the stronger, harder aluminium types that is artificially aged and heat treated only has a yield strenght of 240MPA, so it's almost 3 times as weak.

Also, aluminium has a very nasty way of fretting etc. That means that threads eat into eachother and that it damages the surface on a microscopic scale. Reusing it increases the chance that the threads shear off the bolt the next time it's undone.
Steel is less susceptible to fretting.

It's quite common practice not to reuse aluminium bolts in engineering practices. BMW TIS also states this.

And BMW doesnt recommend single use in all cases. Only in cases that stress or change the material properties of bolts.