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Worn Connecting Rod Bearing Cylinder 4

Before i start this thread i do not have a spun or thrown bearing, it is simply worn and needs to be replaced.

After countless hours of trying to find out what was making my car have a weird noise i got a mechanic to come out and take a look at it, he said its neither a spun bearing or a thrown one because it would be undrivable, i can still drive the car and he said its just worn, he said i can either leave it and not drive it under heavy load or take the engine out and replace it myself.

I have a 2010 Hyundai genesis 2.0t model that i will be pulling the engine out, instead of replacing the whole engine for 2k i decided that i will just replace the failing bearing, the noise isnt some crazy knock or slap like ive seen before and all it is, is a small rattle, i took a jump over to the car forums and they are all insisting that i just replace the engine and i don’t have the money to do that and honestly they are just being assholes about the whole thing. (thats what i get for having a tuner i suppose)

What i will be doing is pulling the engine out since the #4 cylinder cannot be reached by just dropping the oil pan so im forced to remove the whole engine from the car and get underneath it. Now i understand that the crank or the journal might be bad so im expecting to replace that if its in bad shape and not usable.

What i plan on doing is removing the bearing and seeing if i need to compensate it with using an oversized bearing IF NEEDED or just getting a factory one, with that being said is it actually possible to just replace this worn bearing and be good to go or is the engine totally toast like previous people have told me… I need some advice on what to do or the steps i need to do before starting this… Any help is recommended.

How could you know it’s #4? And if one bearing is worn, the rest probably are, too. I question the diagnosis, I’d get a second opinion before going to this trouble.


The odds of a bearing being worn out on one cylinder only with everything else being fine is about zero. If one is badly worn the others are not far behind.

As to installing a new or oversize bearing there are some caveats to that. If the crank journal is badly worn and/or the rod big end beat out a new standard bearing won’t improve things very much.

Generally speaking, the next size up on bearings is .010 oversize. The odds of the crank journal being worn enough to fit an .010 bearing is also about zero.
Some parts manufacturers may offer an oversize bearing that is .001 to .003 over. This MIGHT help. A lot depends on how worn the crank journal is, whether the journal is tapered or egged badly, etc. I have no idea if a 1 to 3 oversize bearing is offered for your engine.
This is where a set of micrometers comes in handy.

IF the one journal and bearing is in bad shape and the others at least tolerable it could be that the oil galley in the crankshaft has sludged up and cut off oil flow to some degree to that bearing.

There are a lot of ifs here. Hope some of that helps.


i appreciate the reply, the reason how i know its from cylinder 4 is because when i remove the cap that goes to the spark plug it instantly goes away, no sound what so ever so i atleast narrowed it down to that single one instead of multiple ones for now. When i mean replacing the worn bearing i meant the other bearings aswell not just that one as i figured since im pulling the whole engine might as replace the rest of the connecting rod bearings also.

It’s entirely possible replacing that single bearing will make the noise go away. But there’d have to be a corresponding explanation why only one bearing is worn out, and the others aren’t. It’s certainly possible only one is worn enough to make a noise, but seems unlikely the others aren’t close to the same worn-out condition. They just aren’t making any noises yet. Perhaps you have some reason though to believe whatever happened to cause this only happened to one bearing. Do you?

You don’t say how many miles are on your engine or if it has ever overheated, run low on oil, or oil and filter maintenance was ever deferred, if there’s a known history of number 4 bearings problems on this particular engine design, etc. Adding some of those details might help other’s give you an estimate of your chances of a single bearing repair.

BTW, that’s a good diagnostic technique of how you figured out it was number 4!

The oil hose going from the engine to the oil filter had a small leak that i never noticed as it would run down the hose line and just never drop off the car or puddled as it would only drop when driving it or the oil was actually being heated. I went to the store and not even 2 miles from my house is when my CEL came on ( the computers in these cars are very smart ) i decided to check the oil and of course it was very low and i instantly did a oil change aswell as replacing the line in question. It could be from me beating the hell out of it also which now i know i cant be flooring it everywhere i go… I figured since im pulling the engine i might as well replace all the connecting rod bearings. I figured once i removed those and looked at the crank and clean it up, make sure no crazy lines in it or scouring and lube the hell out of it aswell as checking the main bearings i can get away with it. You guys are giving me hope about all of this instead of just telling me the engine is toast… I understand if the crank is messed up i will have to replace that or shave it down and just use a oversize bearing…

Its total crap but for some reason on these engines the bearings are different depending on factors, the only way to tell which bearing you need is to actually take the existing ones off and see the color and the leter :wink:

The bearing – which is really just two cylindrical shells sort of stuck to the journal – is made of a special kind of metal composition. I think the inner part (that you normally can’t see) is a copper alloy. And the outer part is a tin alloy. Oh oh, I can already hear the typing telling me I don’t know what I’m talking about … lol . …

Anyway, when the outer part wears then you can start to see the inner part by the color difference. If you can see that other color you know the bearing is on its last legs. It’s better it be on its last legs than completely worn out though. Last legs gives you a chance at least there’s no crankshaft damage.

Good idea to plan on replacing all the rod bearings while the engine is out. It will give you a chance to decide on the crank main bearings and that pin that holds the piston to the rod at the other end too.

I expect you already know this will be a fun, but very time consuming project.

Oh i understand it will be very time consuming, Im going to tow it to the new house im moving into and luckily my dad being a newly retired military guy all he has is time on his hands and believe it or not he use to be a heavy wheel mechanic so atleast i have someone who knows a little bit about what were attempting… What better retirement gift to give him then to have a solid few days of father son bonding time working on a vehicle :wink:

And thank you for letting me know about the different metal compositions, i don’t know if it applies to every vehicle or only certain ones but we will be able to find out when we open her up!

If production engines use anything but “standard” sized bearings, that means the factories quality control or the equipment used to machine crankshafts is in very poor condition and instead of scrapping defective crankshafts they re-machine them undersize and install oversize bearings to avoid having to scrap the crank…Trying to rebuild today’s engines is loves labor lost. Locate and install a good, complete, used engine…

Wow, I didn’t think ANY manufacturer still sorted bearing shells to achieve the proper oil clearance! IF and that’s a big IF, the crank journal is not damaged you MIGHT get away with a thicker shell to get the proper oil clearance. As you posted, replacing all the rest of the bearings is in order. If the crank is damaged, IF you can find a crank grinding shop to re-grind the crank to fit undersized bearings, that should fix things. If you can’t find a shop, buy a new crank from Hyundai, a set of bearings and plastigage and have at it.

As for why it failed first… If the oil pump is at the front of the engine, #4 is at the end of the oil pressure path so likely the first to wear out. Or as some suggested, sludge is lowering the oil flow. That’s a bit tougher to fix without completely tearing down the engine and boiling out the block and heads.

Good luck!

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I recall several Asian imports that used bearings sized to the OD. It’s been a few years so the makes and models escape me. But the color coding indicated the outside diameter of the bearings.

I found this explanation re Honda color coded bearings

They don’t. They now use something called “statistical process control”. That’s essentially just the application of statistics to the manufacturing process, the result being that the manufacturer controls variation in the process rather than inspecting to tolerances. These systems allow the manufacture to keep all the critical dimensions far, far more exacting with far less variation than inspecting and sorting. By monitoring the distribution curves of critical dimensions of the output of the process, the manufacturer can also identify a process beginning to go awry and correct it rather than fixing it after it produces widely varying dimension. It also allows the manufacturer to determine things that are effecting the output, like machine maintenance and operator variability, and build in preventative measures to prevent their effects.

Apparently, Honda still does.
They are measured and stamped on the block and crankshaft and rods.
There are six flavors (stamped and color coded) of bearing to match the actual variances.
Just went and verified that by searching on OEM crankshaft bearings for a 2012 Civic L4.

I am a disciple of Dr. Deming!

But I think Hyundai does not have control on their crank and saddle machining given the listings for different bearing shell thicknesses in the manual picture he posted. Hence my surprise. GM hasn’t used fitted pistons or bearing shells since they adopted Deming’s methods.

Wow, That must have something to do with very small oil clearances used in engines these days. Not even statistical process control can create those tolerances.

You know you cannot take out one crank journal, right? I think that if you are going to pull the motor, the least I would do mike all the journals. If any are beyond spec, send the crank to a machine shop and have the journals turned and put in the right oversized bearings. There are too many things we don’t know, how many miles, what is the condition of the rest of the engine and car. What are you hoping for? Six more months? If so, just replace the bearing halves on that rod, use plastigauge to check how it measures before you reinstall it.

On engines with oil pans that can easily be removed I have occasionally replaced the rod bearings with standard or when available .001 under inserts with varied success. One 3.8L Buick with 200,000 miles went another 100,000 miles before the owner moved away driving the car.

The sound of a failing rod is somewhat unique, as in Rod Knox, and if heard and immediately taken care of the engine can often be saved, but not always. More often than not no one pays any attention to the noise until it overwhelms the quadraphonic sound system and the rush hour traffic around them.

And people are amazed at the damage done when a rod breaks loose.

Just curious, how is that pin that holds the piston to the rod on the far end lubricated? Is there an oil hole that runs lengthwise inside the rod and exits at that pin? And what takes on the bigger force, that pin, or the bearing at the crank shaft side? I don’t think I’ve ever heard a complaint here about the piston pin failing.

All very technical and sage advice, But I would throw some mystery oil in in, drive it till it drops then put a new engine in,

The pistons usually have a drain from the oil ring to seep lube to the piston pin. An old hot-rodders trick is to drill a small hole in the top of the pin bore in the rod and then chamfer it to capture oil splash but with a bearing (bushing) pressed into the rod and full floating pins.

With pressed pins, the only movement is between the piston and pin, so that’s an aluminum “bearing” surface from the pin to the piston that is not pressure fed.

The pin takes every bit as much force as the crank end but it has very little rotational speed. Maybe that’s how it gets away without a pressure lube.

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