S65: Will replacing rod bearings alone "fix" rod knock?

[ocd]

Experienced engine experts please chime in.

My friend found a great deal on an e90 M3, but the engine is noisy and the owner claims bad rod bearing(s). Will replacing the rod bearings alone "fix" the issue and remedy the knock, or at this level of damage is an engine rebuild in order?

[Someone?]

Wouldnt mess with it if i was your boy, could end up costn at the very minimum probably 10 to 15k.

[4corners]

You won't know until you take it apart.

[BPMSport]

You can't really say. If you catch it *really* early, you might be able to get away with just changing the bearings. But usually by the point it's audible enough, there's a likely risk of crank damage.

[SenorFunkyPants]

There is always a chance that the engine noise is nothing to do with the rod bearings - usually the only time you have to diagnose an impending rod bearing disaster is literally just before the engine fails. If the engine noise has been around for a while then it could well be something else. Your pal should take an experienced BMW M3 mechanic along with him for a listen.
Choice 2 is to look around for a second hand engine and do a straight swap.

[Petros]

Originally Posted by ocd

Experienced engine experts please chime in.

My friend found a great deal on an e90 M3, but the engine is noisy and the owner claims bad rod bearing(s). Will replacing the rod bearings alone "fix" the issue and remedy the knock, or at this level of damage is an engine rebuild in order?

I dont know how much of a "great deal" your friend is getting. Unless the deal is great enough to be much cheaper even with the potential cost of an engine rebuild compared to buying another car that is problem free, I think he should forget it.

Also, what hasn't been mentioned yet is if the bearings have worn down badly enough to the extent of making sounds, there is a possibility they scored and damaged the crankshaft journals. It can turn out to be a more expensive repair than you thought.

[BPMSport]

Originally Posted by SenorFunkyPants

There is always a chance that the engine noise is nothing to do with the rod bearings - usually the only time you have to diagnose an impending rod bearing disaster is literally just before the engine fails. If the engine noise has been around for a while then it could well be something else. Your pal should take an experienced BMW M3 mechanic along with him for a listen.
Choice 2 is to look around for a second hand engine and do a straight swap.

I disagree that the noise is indicative of an immediate failure. Obviously it's going to fail with that noise at sometime in the future, but it might take over a hundred miles or a serious beating before letting loose completely. The longer you let it persist, the higher the likelihood of the crank being damaged.

[MilehighM3]

It's completely possible that it's a defective pulley or cracked and damaged belt as well. Without hearing the noise and seeing the car, it's impossible to diagnose. As others have mentioned, you won't know the extent of the damage until disassembly is done.

[regular guy]

The amount of time the engine has is more dependent on what went wrong (or is going wrong). I had one engine that developed a ticking sound and I drove it for 1000 miles as the sound got progressively louder and louder. The bearing clearances were getting bigger and bigger due to a shoddy rebuild where the guy didn't clean the crank before installing (at least that was the theory at the time). I've also seen less than two miles from the time the engine starts ticking until the time it's knocking so loud you think it's going to throw a rod. That was a case of a spun bearing. So there's no one size fits all to estimate how much time the engine has on it.

Last year I bought a 2008 M3 with a blown motor. That car had a racing clutch, roll cage, and brand new supercharger on it when I bought it. PM me and I'll tell you how much I paid and you can give that to your friend to compare. I'll also be able to give you some no-BS ideas what you're looking at for expenses with different scenarios of engine damage. That should help him figure out if he wants to move forward or not.

[bigtracing]

RG hit the nail on the head with that post. mine started making noise a few miles before it spun. If it's already making noise if i were buying it i would go into it assuming it needs a crank then I could weigh out if I was getting a deal or not. I would definitely get a PPI on it it could be a hundred other things making the noise

[ocd]

Thanks for all the feedback guys. Getting the car PPI'd would be awesome, but the particulars of the situation won't allow for it. I'll go with worst case scenario of a used motor swap.

Anyone know the general cost w/labor?

[bigtracing]

Your looking at a lot of money and time. There are usually used motors on ebay for $5-9k. Then I don't know how many hours bmw specs but I'm sure it's up over 40 labor hours to do a full swap. If you were to rebuild it. rods are $250 a piece to replace. If the crank is damaged it's $2500 for one of those gaskets are going to cost you $500 at least. main bearings are 500 rod bearings are 400 etc. etc. plus labor to rebuild it plus removal and install labor. I'd say if your getting a really good deal and can get a deal on labor or do the labor yourself then jump on it if not for the price of the car plus cost of motor swap/rebuild + time aggravation (lots of parts come from germany or are back ordered) you can buy a more expensive one.

[Someone?]

Originally Posted by bigtracing

Your looking at a lot of money and time. There are usually used motors on ebay for $5-9k. Then I don't know how many hours bmw specs but I'm sure it's up over 40 labor hours to do a full swap. If you were to rebuild it. rods are $250 a piece to replace. If the crank is damaged it's $2500 for one of those gaskets are going to cost you $500 at least. main bearings are 500 rod bearings are 400 etc. etc. plus labor to rebuild it plus removal and install labor. I'd say if your getting a really good deal and can get a deal on labor or do the labor yourself then jump on it if not for the price of the car plus cost of motor swap/rebuild + time aggravation (lots of parts come from germany or are back ordered) you can buy a more expensive one.

If the engine has to come apart your lookn at some serious cash, cause unless your a Skilled BMW engine builder you cant rebuild it yourself, it nothing like a American V8 that are simple to rebuild.

[tom @ eas]

Originally Posted by ocd

Experienced engine experts please chime in.

My friend found a great deal on an e90 M3, but the engine is noisy and the owner claims bad rod bearing(s). Will replacing the rod bearings alone "fix" the issue and remedy the knock, or at this level of damage is an engine rebuild in order?

This M3 came in for rod bearing knock, the crank was badly scored.



More info in this thread:

eas | S65 Rod Bearing Replacement: An ongoing "Journal"
http://www.m3post.com/forums/showpos...&postcount=231

His engine is currently being replaced at BMW:

BMW NA Approves New S65 Engine Replacement Due to Bad Rod Bearings
http://www.m3post.com/forums/showthread.php?t=945034

Unless you are fully prepared for the worst, I would probably walk - there's plenty of other M3s on the market for sale. Hope this helps in your decision.

[SenorFunkyPants]

Originally Posted by ocd

Thanks for all the feedback guys. Getting the car PPI'd would be awesome, but the particulars of the situation won't allow for it. I'll go with worst case scenario of a used motor swap.

You are not giving folk much info to work with...if you can't do a PPI then you are basically buying it blind. If you can't hear the engine then you can't drive the car either - it could have a bent frame in which case its worth salvage money.

[bigjae1976]

Once you get the knock I would assume the worst. The crank might still look OK but a rod might be ovaled...who knows what else.