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Old 05-10-2017, 07:22 PM   #1
NZ00Z3
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Changing big end bearings with Engine in the car

Hi

Car:
- 2000 E46 323i (M52TUB25 engine)
- 120,000 km

Symptoms:
- Slight dull knock from engine at idle
- Cylinder 6 is off the scale (1.5 to 2) on INPA rough running graph, all others are very even (<0.5).

Expected cause:
- Run big end (con rod) bearing on #6

Question:
- How hard is it to remove the sump (oil pan) and replace the big end (con rod) bearings with the engine still in the car?

Thanks in advance.
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Old 05-10-2017, 07:33 PM   #2
dogsgottaeat
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Unless you are a proctologist, pull the motor out of the car.
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Old 05-10-2017, 11:00 PM   #3
jjrichar
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Big end bearings can be done. Below is a link for an M3 DIY for the same job. A significant DIY, but not as big as pulling the engine. This was done extensively on the M3 due to bearing issues in early engines. The method is pretty much identical to your engine. Second link is to a project I did on the engine a few years ago that gives you a good ideas on what is in the engine. It's for an M54, but the majority of what you will be touching is the same.

http://www.m3forum.net/m3forum/showthread.php?t=455681

http://forum.e46fanatics.com/showthread.php?t=899347
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Old 05-11-2017, 12:16 AM   #4
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I replaced connecting rod bearings couple weeks ago with engine in the car. It is very much doable although a bit annoying.
There are numerous DIY posts about doing oil pan gasket which cover most steps removing everything to get bottom open.

One big suggestions from me is if you have more of a compact type of body then put car on jack stands not too high so that you can lower front subframe onto the ground.
Then go a step further by unplugging sensors on both front wheels, remove and support brake calipers to car body, remove top 13mm nuts holding struts, and finally slide the whole subframe towards the front of the car.
It took me maybe 15 more minutes to remove and install those extra parts but made it much more convenient to work under the engine.
The crucial part is raising car just enough to be able to work under there but also be able to let the subframe rest on the ground. Raise too high and there won't be enough slack in steering lines.
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Old 05-11-2017, 06:45 AM   #5
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Like others said, it can be done. However, if you're experiencing knocking because of a bad bearing, the journals may be damaged and that is nothing you an fix (without a LOT of ugly work) with the engine in the car. You'd have to remove the crankshaft, and if you're going that far, it would be MUCH easier to remove the engine.
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Old 05-12-2017, 06:49 PM   #6
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And to play car whisperer, at 120k kms, most BMW engines are still very nearly new.
For a connecting rod to fail, it'd have to have lead a very rough life, or only had one oil change, ever.

Have you given a close listen with a stethoscope? Something like a failed dual mass flywheel could be knocking...

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Old 05-19-2017, 05:49 PM   #7
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i have done it today, its about an 8h job. you need special tools and to lift your car. my rod bearings have been running for 80k miles and thats how they looked like:
IMG_20170519_155011
all bearings were close to copper, except for cylinder 4 which was completely messed up.

Just remove the oil pan and you can replace them easily. get a friend to help you
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Old 05-19-2017, 05:57 PM   #8
PancakeBimmer
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Quote:
Originally Posted by gigu View Post
i have done it today, its about an 8h job. you need special tools and to lift your car. my rod bearings have been running for 80k miles and thats how they looked like:
IMG_20170519_155011
all bearings were close to copper, except for cylinder 4 which was completely messed up.

Just remove the oil pan and you can replace them easily. get a friend to help you
Ohh wow, that is so much worse compared to bearings I removed at 188k. Was the clearance too big or bearings spun out?
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Old 05-20-2017, 01:25 AM   #9
gigu
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the car has 127k miles now. i only have a vague promise of the pre owner, that the rod bearings were replaced at 55k miles. i dont believe that they have been in longer. other pics that i have seen of rod bearings around 50k miles look similar. i hope this is just normal wear of the bearings.

IMG_20170519_WA0026

most people replace them at a 50k miles interval
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Old 05-20-2017, 01:39 AM   #10
PancakeBimmer
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Quote:
Originally Posted by gigu View Post
the car has 127k miles now. i only have a vague promise of the pre owner, that the rod bearings were replaced at 55k miles. i dont believe that they have been in longer. other pics that i have seen of rod bearings around 50k miles look similar. i hope this is just normal wear of the bearings.

IMG_20170519_WA0026

most people replace them at a 50k miles interval
Oups, my bad. I just notice that you have M3 which is I guess more prone to bad bearings wear.
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Old 05-20-2017, 02:01 AM   #11
gigu
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Quote:
Originally Posted by PancakeBimmer View Post
Oups, my bad. I just notice that you have M3 which is I guess more prone to bad bearings wear.
same here, sorry, just saw i posted this in the regular e46 forum
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