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Hi there,
Due to a knocking noise from the engine on my MY2004 156 2.0 JTS I might need to replace one or more rod big end bearings. I've been working with cars for many years and have done all types of engine jobs except tasks relating to crankshaft and rods. Has anybody here replaced big end bearings?

I've been looking at the Alfa OEM parts catalog at 7Zap, CONNECTING RODS AND PISTONS ALFA-ROMEO 156 M.Y.2002 BZ/DS (2001-2005).

It seems like there are several dimensions for the bearings and I'm not sure which to choose. I guess the different dimensions correlate to if crank and rods has been grinded? Do I need to measure the rods and crankshaft to get the right?

Can this job be done with the engine still in the car or do I need to get it out?

All help appreciated! :)
 

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Hi there,
Due to a knocking noise from the engine on my MY2004 156 2.0 JTS I might need to replace one or more rod big end bearings. I've been working with cars for many years and have done all types of engine jobs except tasks relating to crankshaft and rods. Has anybody here replaced big end bearings?

I've been looking at the Alfa OEM parts catalog at 7Zap, CONNECTING RODS AND PISTONS ALFA-ROMEO 156 M.Y.2002 BZ/DS (2001-2005).

It seems like there are several dimensions for the bearings and I'm not sure which to choose. I guess the different dimensions correlate to if crank and rods has been grinded? Do I need to measure the rods and crankshaft to get the right?

Can this job be done with the engine still in the car or do I need to get it out?

All help appreciated! :)
First of all you need to remove your old bearings and inspect the crankshaft. Since you have knocking, you must verify that the crankshaft is still usable, which is unlikely. It would have to probably be reground or best replaced.

Honestly, you should give the job to the machine shop.

However, if you wan't to tackle this yourself, remove the crankshaft, inspect it, you will at least need a machine shop to polish the journals, after that you need to measure all of the clearances (preferably using micrometers that are properly zeroed) and adequately choose the correct bearings. You can reference to the factory manual for correct clearances.

This is not like changing wheel bearings, extreme caution and precision must be used. I would say this warrants for a complete engine overhaul as you have sent bearing material through the oil pump and the rest of the engine. Might be best to just replace the engine...

Wish you luck!
 

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Alfa 159 2.0 JTDm Lusso 6sp.
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......after that you need to measure all of the clearances (preferably using micrometers that are properly zeroed) and adequately choose the correct bearings. You can reference to the factory manual for correct clearances......



Wish you luck!
......and use this to double check bearing assembly clearances.....


 

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Discussion Starter · #4 ·
Thanks for your feedback! I haven't looked deeper into this yet. Hopefully there's some thing else that knocks.. If not, an engine swap sounds like the best choice, I guess a restoration will cost more.

Are there any other known issues on theese engines that causes a knocking noise?
 

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The OE bearings are graded and colour coded. Aftermarket bearings are not. When I've done work like that, I just use Federal Mogul group parts (AE, Glyco, Nural, Payen, Goetze).

It goes without saying that an engine shouldn't wear out a big end bearing. It needs an operational fault to do that.
 

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Even in high mileage engines? ex. 350K miles? (JTD)
Last time I checked my aux pulley, I noticed some axial play in the crankshaft.
Sounds pretty much like like the average diesel, but that's something I'm not confortable with.
 

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Yes, but is that normal due the mileage?
Some people say bearings will never need changing unless you have some problem with the lubrication. Others, that's something that gets worn (not in catasthrophic way) when reaching high mileages.
 

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Thrust bearings are loaded and wearing when you declutch. Do you start the car with the clutch pedal depressed?
 
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