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Discussion Starter #1
Hello everyone, new to the group and actually new to bmw. My father was a Porsche Audi tech and my last car was a c5 RS6 and I Just acquired a 2008 m5....I have to say this is a superb vehicle and I feel the quality used in bmw far surpasses the Audi’s I’ve owned, anyhow let’s discuss my giant problem. My new m5 had rod knock. When we opened it up it looked like we were gonna get off easy with the crankshaft being good, upon further inspection that is not the case. I’ve got the engine ready to pull out and was wondering if there are any other things I should be doing while undertaking this process, I know the smg pump and other items commonly known but I’ve only owned this car for a week or so. Any help or pointers would be much appreciated. I’ve already ordered the rod bearing kit with motor mounts, seals etc from turner motor sports. Although I’m having a hard time sourcing a crank under a million dollars haha.
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I hope you paid according for the car. How many miles? Since the engine will be apart for quite some time and you or your father are skilled techs, you should also tear down and inspect both oil pumps, per the G.A.S instructions.
Also since you asked:

Front end engine:water pump, idler pulley, and tensioner pulleys, voltage regulator (or whole alternator), belts
Top end: cylinder head temp sensor (cheap), check age of throttle actuators/if they were rebuilt, starter (really hard to get to but engine is out anyways so easy and cheap), potentially thermostat since most of the car will be apart
Cylinder head: VANOS orings on solenoids, all injectors, plugs, coils (if necessary).

Other:
Chain guides, BMW has known issues with chain guides on their V8s, unclear if this is an issue on the S85, there don't seem to be the same catastrophic failures seen on the V8s.
Power steering rack and/or lines. Likely you have leaks somewhere, all of mine did.
Not going to mention RMS and FMS since crank has to come out and those are part of the job.
Looks like you guys kept the whole suspension attached to subframe and the struts. But the front end suspension links and inner and outer tie rods do need to be replaced after 100k miles to keep it BMW tight.

Not going to mention SMG stuff that is a separate subject.

Welcome to the club!
 

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Discussion Starter #3
I got the car for 6k and it has 130k miles. Engine compartment, interior etc are extremely well kept. Wasn’t sure if I needed to do piston rings. And hone cylinders. These are hard things because where do you stop haha. That’s how my 70 corvette started, just going to put a mild cam and then 25k later wondering what happened 😂.
 

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That's a reasonable price, I really like the monaco red seats and it's an LCI. I assume the rod knock was a known issue and reason for the sale right? I'd deduct at least an automatic 6k based on that, and seems like you did as well. Sad the the prior owner neglected to address that since it's such a known issue. You can get a stroker crank and use stock pistons and rods, I think the cheapest stroker crank is like 5k. It really helps on the torque, since the S85 is lacking in that department. Also doesn't seem like the work involved would phase you or your dad. There have been issues reported here and there of cracked valve springs, I think this is an issue with spring fatigue that wasn't really factored in given how high the RPMs can be on these and with all those miles, I'd consider Supertech springs, they are like 500 for the set IRC.
 

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Life Cycle Impluse. Often referred to as a facelift. BMW speak for mid cycle updates to the platform, generally 3-4 years after the first gen comes out.
 

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Discussion Starter #7
Wow I didn’t know there was a difference so that’s an added benefit. What do you do about the SMG just preventive? Seems like a rebuild kit or maintenance kit is like 3500
 

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Well as you can see on this board like 60% of the threads are issues relating to some aspect of the SMG. In general the gearbox never fails, it's every single thing attached to it that has issues, mainly the hydraulics and some of the wiring.
 

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Discussion Starter #9
you know it’s funny, my whole life my family has been VW Audi Porsche but when I got this car, even my father who is a devout Audi guy really thinks this is an amazing car. And rightly so because it is! It goes both ways but never again will I let my stubbornness or pride Tobin the way of enjoying a car...my Rs6 was great and I loved that car but I’m more excited to get this beauty on the road again! Such an amazing machine and worth every penny in repairs.
 

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The E60 is pretty easy to work on compared to ANY Audi. I really don't care for the chassis dynamics of the RS6, I like RWD. You already know German cars tend to be money pits, and the E60 platform has it's own issues, and S85 has only like a few fatal flaws that I seem to be aware of :1) rod bearing and scored crank. 2) leaking fuel injectors causing hydrolock, 3) broken valve springs, which could be a major or minor thing. Everything else does not seem to be fatal.

The SMG has several issues, and that's why people prefer the manual or seek to covert theirs to a manual.
 

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BMW seems to have valve seal issues also on many of their engines. This leads to excessive oil consumption which is not uncommon on the S85. Since your engine will be apart, you may want to look at the valves and replace the valve seals. Not hard for you guys.
 

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Discussion Starter #12
Thanks for all your help I really appreciate it! I will definitely check out more than I was planning on doing.
 

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There are like 10 years worth of posts here so there's alot to read. Troubleshooting the SMG won't be so hard for your guys since that's what your dad does, but the manual is so much better to drive, consider a conversion. There is a youtube series about that by E39source.
 

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Discussion Starter #14
As fun as it sounds I think the SMG is pretty cool! I’m sure that will change once I ha e a failure lol
 

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When I first saw the pic of the whole front end removed I laughed, it’s clear you guys are Audi/VW folk. You can actually drop the engine and trans straight down, but pulling it from the front saves the work of removing the secondary air valve thingies. I’d be interested in how you guys decide to remove the heater hoses. I just cut mine, but that car was a wreck anyways.
 

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Discussion Starter #16
Yes that’s how you do it with Audi’s and Porsche’s as well but the bumper was already off and we decided what the heck lol. We didn’t cut anything......yet😂. With that stroker kit are you sure it uses the same rods, the kit I saw was like 14k I could t believe it.
 

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There are different options for stroking. You can do your own research but I seem to recall that the most Vanilla flavor a 5.2L displacement which makes it more square and basically only changes the throw on the crank as well as the counterweights so the rods and pistons can be reused.

you can get your crank reground and go with oversized rod bearings. That would be cheapest approach.

VAG cars are packaging nightmares but they do pull it off at the cost of being hard to service and really nose heavy. The M5 is pretty easy to work on by comparison.
 

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Discussion Starter #18
Yes my Rs6 was horrible, driver side chain tensioner replacement pays 3 hours, passenger side pays 20 😂. And it doesn’t stop there. And in response to your previous post about the all wheel drive, yes that killed the experience so much with my Rs6. Just really numbs the experience. I’m so excited to get this baby going again👍
 

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Yeah I think Audi are great for winter and rally driving, but just a bit too much work.
I’d advise looking at regrinding your crank and going with the ACL 0.25mm/0.010” oversized bearings to make up the difference. There’s a bit of research you will want to do to get the desired bearing clearance since the factory specs are far too tight and that’s what caused the issue in the first place, but ACL has come to the rescue with an oversized bearings.
 

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There are different options for stroking. You can do your own research but I seem to recall that the most Vanilla flavor a 5.2L displacement which makes it more square and basically only changes the throw on the crank as well as the counterweights so the rods and pistons can be reused.

you can get your crank reground and go with oversized rod bearings. That would be cheapest approach.

VAG cars are packaging nightmares but they do pull it off at the cost of being hard to service and really nose heavy. The M5 is pretty easy to work on by comparison.
I only know of Troy’s 5.2 L motor which many refer too as a “stroker” even though all of the 0.2 L displacement increase is acheaved via an over bore.

This route is most cost effective Since rods and crank are retained.

This solution makes sense in the case of hydolock due to injector failure that ruins pistons and cylinder bores.

If a crank has a spun bearing so bad that it cannot be ground to use oversized bearing shells then the more expensive 5.5 L stroker would make sense.
It uses a custom stroker crank, rods and perhaps pistons with a custom pin height or shorter rods to use stock pistons.

I would never entertain a common practice of welding up spun journal and regrinding for the s85 motor

A 5.2 L actual stroker motor by offset grinding crank to Honda 1.8 “ journal diameter is an interesting idea.
It may be the most cost effective in case of bad crank
 
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