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Bad Connecting Rod Bearing?

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Hey guys new member here. Recently bought my 2000 Porsche Boxster S back in June and ran through plenty of problems since day 1 but today im a little lost. After a failed oil cooler, oil pump solenoid, new spark plugs, new window regulator, new AOS; im now stuck with a knock coming from from the driver side of the engine (U.S.) I haven't needed to get into the engine since I haven't had serious problems until now. Looking at similar knocks on YouTube, I think its a failed rod bearing. CEL came on for a Cylinder 6 misfire. I read at other posts about getting to them through the oil pan but can't find how. Besides pulling the oil pan, what else do I need to crack open? Do I need to remove the cross bar? By the way, I know something is going on because I pulled the oil pan off already and found alot more metallic flakes from wear and tear than usual. Im pretty sure the previous owner didn't do a oil change when he was supposed to. At this point, Im going to college with 5 classes and launching a business soon, so I hope im not stuck with a major rebuild. Planning to post pictures and video tomorrow. Thanks.

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Welcome to Renntech!


"I pulled the oil pan off already and found alot more metallic flakes from wear and tear than usual." Based on this description, I'm sorry to say but the only proper way to correct this is a complete tear down and clean up of the engine. The rest of the other issues will also need be addressed once everything is apart. How does the oil filter look like?

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2 hours ago, Ahsai said:

Welcome to Renntech!


"I pulled the oil pan off already and found alot more metallic flakes from wear and tear than usual." Based on this description, I'm sorry to say but the only proper way to correct this is a complete tear down and clean up of the engine. The rest of the other issues will also need be addressed once everything is apart. How does the oil filter look like?

The oil filter looked normal with casual wear.

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6 minutes ago, Harman2907 said:

The oil filter looked normal with casual wear.

If you find metal flakes in the oil pan, the same debris will be sucked up through the oil pickup tube to the pump then to the oil filter.

Just curious did you cut open the filter, lay it flat, and check both sides?

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It may not be as bad as I thought then. I think as long as your filter is clean, you should be safe.


To inspect for bore scoring, you only need to remove the oil pan and put the cylinder in TDC and stick the borescope into the cylinder wall via the crank cradle.

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4 minutes ago, Harman2907 said:

I can't upload any pictures because they all exceed the 2mb upload limit. I can email them to you if you like to see what the oil pan looks like. Should be able to reach and take out the bearings from the oil pan?


Not a chance.  When you take off the sump cover, you will not seen any bearings.




All the bearings are inside the crank carrier and cases



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You can upload the pics to wetransfer and post the link here.


No, unfortunately you can't take out of even access the rod bearings or any bearings unless you split the engine block. The bearings are all held captive inside the crank cradle (part #14 here http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996-99-05&section=102-00)



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I had a similar problem. 90k miles0n mine - yours?.Perfect service history.Mine was #5.Look at the oil circulation system ,you'll see why it is 5 &6 that fail first.Thanks Jake for that !

Mine had an LN full flow filter fitted and that caught all the debris from the bearing. There was also debris(like yours) in the pan. If you have the OEM bypass filter, the FOM has probably circulated beyond the filter. If so the only option is a total tear down, meticulous multi-stage cleaning and rebuild. Used engine may be a better option unless you are a total M96 geek like Ahsai & Schnell Gelb who lavished thousands of dollars and hundreds of hours on a rebuild+upgrade.

Your old engine may have value to someone who wants the intellectual challenge of a rebuild+upgrade - if it is complete and not butchered during removal. Before you decide ,do the financial research and be sure to include any gearbox repairs that may be necessary (2nd Pop-out or bearing noise). You can easily spend $12k+ on such a project w/o upgrades  and it takes months. Roller ?

We'll help you through the decision making but it is rather brutal.

Let's hope it is just a loose spark plug !


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Bearings usually go out because of oil starvation which usually occur on the track but I dont track my car and I have had to frequently change my oil in the last few months of ownership because of a intermix issue. I still used to Mobil synthetic, but could it be anything else like a sticky lifter or exhaust manifold gasket?


-96k miles.

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The M96 is different.The word "usually" from the Mechanical Engineering lexicon does not apply.

Look at the oil circulation path for the M96, as I suggested earlier and you will see there is  short,direct route for FOM from the oil pickup straight to 5 & 6 . So debris from other wear components hits those bearings even if the car is stationary,in neutral  and the engine is idling. Tracking may cause 'sump' oil to slosh around an dislodge debris from previous incidents (like a failed IMSB from thousands of miles previously). Depending on which filtration system the engine has, the debris is quickly carried to bearings regardless of oil level or g forces.

Once there is debris in an M96 with a stock filter ,the most likely cure is a complete strip,clean and rebuild because that is the only way to remove all the debris. This is the mechanical engineering reality but it conflicts with people's emotional reaction to the cost and with their experience with conventional engines. So they dicker and deny.

The few rational people fit a deep sump, do UOA ,drop the sump plate,fit full flow filter and take many other seemingly needless precautions. Yes this is expensive but not compared to a rebuild.

Yemv and I hope it does.

Edited by Schnell Gelb
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