M9 bedplate bolts. Reuse or Replace?

[miles3719]

Hi all,

About to embark on my main and rod bearing replacement job in my S65. I read in TIS that the M11 bolts are to be re-used and if you do use new bolts then you basically have to put 3 stretch cycles through them thus making them 'used' anyway.

What is the case with the 'funny looking' M9x 97 'fitting bolts (P/N: 11 11 7 838 986), tis makes no mention of replacing or re-using them. What does TIS normally do in this situaton, does it always assume re-use unless specified otherwise?

Just like the oil pan bolts for example, some say 'just replace them' and some are like 'just re-use them'. For me they are in the 'given the price just replace them' category but by the letter of the BMW law, is that correct?

Just after some clarity if anyone has found a definitive recorded answer as while they are cheap in the grand scheme of an engine, they are not THAT cheap that they're just a rounding error.

Cheers,
Aaron

[miles3719]

Watching the M539 assembly video again, if you have to torque up the whole thing with plastigague installed to check the main bearing clearances then remove it all again, you have effectively stretched the bolts already?

So wondering if he used a new set of 'fitting screws' then when assembled for the last time, or used the same set he initially torqued it all down with?

Bit confused here, would love for an engine builder to pipe in and let me know what the agreed practice is or this.

I see that at the end he checks his lines to make sure they match so they are torqued to the right angle once its all said and done

[deansbimmer]

The fitting bolts can be reused.

If you suspect the bedplate had been removed and reinstalled before then it would be wise to replace the M11 main bolts so that they don't have too many stretch cycles on them.

[RocketyMan]

Originally Posted by miles3719

Hi all,

About to embark on my main and rod bearing replacement job in my S65. I read in TIS that the M11 bolts are to be re-used and if you do use new bolts then you basically have to put 3 stretch cycles through them thus making them 'used' anyway.

What is the case with the 'funny looking' M9x 97 'fitting bolts (P/N: 11 11 7 838 986), tis makes no mention of replacing or re-using them. What does TIS normally do in this situaton, does it always assume re-use unless specified otherwise?

Just like the oil pan bolts for example, some say 'just replace them' and some are like 'just re-use them'. For me they are in the 'given the price just replace them' category but by the letter of the BMW law, is that correct?

Just after some clarity if anyone has found a definitive recorded answer as while they are cheap in the grand scheme of an engine, they are not THAT cheap that they're just a rounding error.

Cheers,
Aaron

Couple of things on my last rebuild.

• Not all fasteners that are TTA are TTY
• Don't use power tools on the M9X97. The saddle bolts are thru holes, but they position themselves in the bedplate and CAN BE TRICKY to get out/and/or stuck--go slow as to not strip the threads -- this is why TIS warns about this
• TIS calls to clean and oil threads -- I use moly grease on bottom of cap and light amount on threads because there is alot of threads and don't want any binding or "twisting" on the fastener to be experienced in the bolt (this is really important on something like the VANOS bolts)
• I reused all my oil sump bolts with no problem--they torque all the same-- 10 NM, easy
• When measuring the main bearings, I reused the M11x115 and M9X97 bolts and torqued them to 30NM and 15NM respectively then did like "half" of the 130* angle (was using plastigauge, and also wanted to see "how free" the crank would spin with just a light coating of oil on mains)
• I used a very nice torque wrench that did the TTA and gave a final torque reading once done(it also measured how many times it was used to indicate the number of fasteners tightened, but also still use a paint marker to ID)--I was then able to visually remember this and expect each fastener to be within circa 10% of one another as a good check

If you're really concerned about the bolt integrity, you can measure the "necking down" on the throat of the bolt, and/or overall length when compared to new. The reason why TIS has you practice the important tightening instructions on new bolts is to "work harden" the bolt.

The TIS instructions are kinda tricky to understand. But I would say reach out on here if you are confused, or just rewatch the m539 video and you'll get it, easy.

[miles3719]

Hey RocketyMan thank you for the tips. Luckily I am not going to be the one doing this, I just like to know what TO do, and to make sure that I have all the necessary parts for my (trusted) mechanic to put it all back together.

I ordered a set of M11 bolts anyway, they were actually not expensive here in Australia (cheaper than FCP/ECS surprisingly).

The other question I had if you dont mind. I have

[RocketyMan]

Originally Posted by miles3719

Hey RocketyMan thank you for the tips. Luckily I am not going to be the one doing this, I just like to know what TO do, and to make sure that I have all the necessary parts for my (trusted) mechanic to put it all back together.

I ordered a set of M11 bolts anyway, they were actually not expensive here in Australia (cheaper than FCP/ECS surprisingly).

The other question I had if you dont mind. I have

Hmm..interesting.
I can't imagine this bolt is at all common in the industry...so I'd like to know where you sourced them other than FCP or your local dealer when the price is circa $45 EACH.
https://www.fcpeuro.com/products/bmw...m5-11117838986

The main bolts are the same story just at around $30 EACH.
https://www.fcpeuro.com/products/bmw...m3-11117834141



When 10 are needed, of each, this is really quite spendy. Nearly $750 for just bearing bolts. Then not including the 26 perimeter bolts. Maybe you have a new plug on bimmer bolts?

[miles3719]

My mechanic got them from the BMW dealer... List price was only a little higher but price 'to me' was

List price was AUD$ 20.36 + GST (10%) which is about USD$13.88. I got them for $2 each less than that.

I should probably reserve judement until they actually arrive as who knows if they will be actually right or not . The M9 ones were about USD$33.27 each

[RocketyMan]

Okay. Hmm..just a little less in price. So that's nice at least.