s62 Crankshaft repair/grinding - BMW M5 Forum and M6 Forums
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post #1 of 10 Old 19th March 2019, 06:15 AM Thread Starter
dranik182
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s62 Crankshaft repair/grinding

Hello everyone!
I just took apart engine after spun bearing and wondering if anyone has expirience in s62 crank repair?

There are 2 options:
1. to weld and grind it to nominal size:
-which is more expensive, at least 500$
-the only company i know in socal who are able to do that is marine cranckshafts - waiting time at least 6 weeks
-once they did crank for my s85 and it still runs great

2. to grind it for undersized bearings
- bmw has undersized bearings in catalogue +0.25 and 0.50
- crank shop i found nearby estimated 50$ to grind one rod journal - the guy said that he can try 0.25, but most likely damage is beyond that point so 0.50 is my option

So i have couple questions. I believe crank is hardened or has some coating on top of the journal, so is it ok just to grind it without any other proceedures? Also can i grind only 1 journal, or i have to do all 4? Will it affect to a stroke somehow?

Any opinions highly appreciated!
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post #2 of 10 Old 19th March 2019, 07:30 AM
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post #3 of 10 Old 19th March 2019, 07:46 AM
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Quote:
Originally Posted by dranik182 View Post
Hello everyone!
I just took apart engine after spun bearing and wondering if anyone has expirience in s62 crank repair?

There are 2 options:
1. to weld and grind it to nominal size:
-which is more expensive, at least 500$
-the only company i know in socal who are able to do that is marine cranckshafts - waiting time at least 6 weeks
-once they did crank for my s85 and it still runs great

2. to grind it for undersized bearings
- bmw has undersized bearings in catalogue +0.25 and 0.50
- crank shop i found nearby estimated 50$ to grind one rod journal - the guy said that he can try 0.25, but most likely damage is beyond that point so 0.50 is my option

So i have couple questions. I believe crank is hardened or has some coating on top of the journal, so is it ok just to grind it without any other proceedures? Also can i grind only 1 journal, or i have to do all 4? Will it affect to a stroke somehow?

Any opinions highly appreciated!
Assume the scoring on the crankshaft was severe enough to the point that it requires this work?



Do you have any additional details on how/when you discovered the spun bearing ? And if you continued to drive on it afterwards?
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post #4 of 10 Old 19th March 2019, 04:42 PM
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If you grind the crank to remove metal, won't you need OVERSIZED bearings?

Regards,
Jerry

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post #5 of 10 Old 19th March 2019, 05:25 PM Thread Starter
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Quote:
Originally Posted by gsfent View Post
If you grind the crank to remove metal, won't you need OVERSIZED bearings?



Regards,

Jerry

I thought the same before I read that:
An oversized bearing has the same inside diameter but a bit more material on the outside diameter. An undersized bearing measures the same outside but is thicker on the inside.


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post #6 of 10 Old 19th March 2019, 05:27 PM Thread Starter
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Quote:
Originally Posted by mmzcee View Post
Assume the scoring on the crankshaft was severe enough to the point that it requires this work?



Do you have any additional details on how/when you discovered the spun bearing ? And if you continued to drive on it afterwards?


I bought the car with knocking engine, so I was ready for it)


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post #7 of 10 Old 19th March 2019, 06:36 PM
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The crank will need to be heat-treated after grinding.
I think the best bet right now just to get a good replacement crank and go with standard bearings.

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post #8 of 10 Old 19th March 2019, 10:21 PM
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Quote:
Originally Posted by gsfent View Post
If you grind the crank to remove metal, won't you need OVERSIZED bearings?

Regards,
Jerry
It's just terminology. They are oversized in the critical dimension!

--Peter
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post #9 of 10 Old 19th March 2019, 10:24 PM
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Quote:
Originally Posted by TexaZ3 View Post
The crank will need to be heat-treated after grinding.
I think the best bet right now just to get a good replacement crank and go with standard bearings.
Correct. Some argue that grinding down one size doesn't go through all of the existing heat-treatment, but I would never take that risk.

Agree that a replacement crank will be both cheaper and faster than sending it to Marine Crankshaft. If you do choose to use the existing crank, I would recommend the weld and re-grind approach rather than using (what I call) oversize bearings.

--Peter
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post #10 of 10 Old 20th April 2019, 01:42 AM Thread Starter
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I decided to let marine Crankshafts do their magic and it went out perfect.


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