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Bmw 640d spun bearing, questions as to how, and Next steps

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Hi all,

I've got a bmw 2012 640D (diesel) 130k km. I had recently bought the car from my brother so. ive known it to be problem free for a year. It has a full service history. It recently developed a knock in the front bottom end. When I looked into it I found that it was leaking oil from the front end seal, and it had sheared the brass seal and contaminated the oil. When I looked further I found that it had spun a bearing.

I had the car remapped (no other mods) shortly before hand the knock, well there was a bit of time between but I had very little driving for a while due to covid and working from home. Shortly beforehand noticing the issue, I also had the car out for a spin all warm etc. I gave it a hard pull tipping just over 250km/h

I have replaced the car with a similar milage engine and driving it for a while with no problems, I've been driving it fairly easy as it still has the (possibly questionable) remap on the car.

I'm in two minds as to what to do next.

1. Keep the car, frequent oil changes, possibly monitor the timing chain with a scan tool (if possible?). To do this I would remove the map, and go to darkside development get a new remap from them, along with their fmic.

2. Sell the car and buy something else. I'm not too interested in in removing the remap and driving it stock, in my opinion any issue there will just take a little longer to happen if is no remap on the car.

My questions are:

What is it that could have caused this failure, I have read up and can't see much in the way of remaps causing this problem, but the high speed, hard pull seems to fit the root cause a bit more. I have yet to further investigate into the internals of the engine. But what are your thoughts on this?

I'd like to go option 1, but I'm uncertain on the odds of it happening again, or any other issues, and I'm a little apprehensive About the car otherwise, what are your thoughts?

Much appreciated for any input, or thoughts.

Hello

Good choice, the BMW 35/40d is a wall of torque from 1000-5000rpm.

I think the 640d has the N57 engine which unfortunately suffers from the renowned BMW OEM bearing issues which are usually down to quality, clearance and oil starvation issues. In addition the timing chain and tensioner suffers with lubrication issues. These issues also tend to raise there head around the 60-70k mark which aligns with your current mileage.

Diesel remaps tend to increase rail and boost pressure while ignoring OEM smoke limitations which increases mean and peak cylinder pressure that can lead to metal/metal contact on the bearings if the lubrication system isn’t up to spec so remapping needs to be done with this in mind.

regular oil changes will help reduce carbon deposits which lead to build up and restriction in the galleries as well as managing oil temperature, it could be worth monitoring and increasing oil cooling capacity to help this.

having an oil analysis done every time will mean you can preempt any bearing issues and it’s relatively cost effective now around £20.

Have you thought about contacting https://www.hackengineering.co.uk/ or another such BMW specialist for a quote to replace the timing chain and bearings, this should give you piece of mind a good base on which to develop.

Hi Scotty

Thanks for coming back to me. I’ve contacted Hack Engineering, they are too far away to do the work, but I’m waiting to get a quote back from them on parts.

If you’re saying the issue occurs at 60-70k miles, would it be safe to say timing chains should be done a 50k interval to avoid this problem?

So based on what you’re saying I’m considering doing the following:

3-5k oil changes

Use Liqui Moly 2037 engine flush, maybe just once at my next oil change.

Change the timing belt and possibly the bearings.

Get an oil analysis done on my oil changes.

Carry out inspections on the timing chain (https://www.newtis.info/tisv2/a/en/f13-640d-cou/repair-manuals/11-engine/11-31-camshaft/1VnZ8nwR0I)

Does that sound like a good enough plan?

Just to throw something in the mix about the engine flush - me personally wouldn't recommend engine flush products.

Yes they do the job of thinning the oil and making it easier to drop it out and get rid of any gunked up oil - if I was to use a product to do this I would then run the car on a sacrificial oil and swap that out after a few hours of running to make sure all of the flush has been removed.

You can find that with a flush some of it stays in the system (in lines and coolers etc) which when you then add fresh oil dilutes it slightly. It is ever so slightly and I have never heard of issues coming from using a flush product but for me I would use two oil changes to be sure.

That said I would only do that to an unknown engine, so when you get yours rebuilt just keeping on top of regular oil changes should be enough to make sure it stays clean and fresh without deposits building up.

Also as Scott mentioned you can send samples of your oil off to be analysed to see what is going on internally, this will let you know if there is any excess of bearing material getting into the oil; as Scott mentioned would hint to oil starvation to the bearings.

For me 3-5k is where I would do changes; I've always changed my performance cars at the 3k mark for peace of mind.

Hope this helps.

OK good to know, I may go the sacrificial oil change route with a flush on a one time basis and stay on top of oil changes going forward.

Yes I will be doing an oil analysis. Get a base one, at the very least and maybe check every second oil change.

On Scotty's point about their being an increase in mean and peak pressure will effect the oil film, in addition to oil changes, is it worth changing the oil viscosity?

Thanks

OK good to know, I may go the sacrificial oil change route with a flush on a one time basis and stay on top of oil changes going forward.

Yes I will be doing an oil analysis. Get a base one, at the very least and maybe check every second oil change.

On Scotty's point about their being an increase in mean and peak pressure will effect the oil film, in addition to oil changes, is it worth changing the oil viscosity?

Thanks

Hi Ronan,

Further to Dave’s point, stay away from engine flushes, they can induce more issues than they fix especially with vvt systems and turbo feed restrictors.

Regarding oil viscosity, since you’re probably just asking for a little more from your road car rather than running an endurance race I’d be tempted to stick with the OEM approved oil as long as its changed out frequently and there are no issues with high temperatures or lower pressures. If you find the compression and sheer loads on the oil result in high temperatures you could look at using the OEM approved oil for a different market as BMW would often spec a different oil for Australia than Europe for example.

Hi Scotty,

OK thanks, I'll just stick to frequent oil changes.

Would it be smart to do some data logging on the oil temp, and oil pressure when taking the car out for some WOT pulls, to see if everything is OK. Possibly recheck on a hot day.

Thanks

Ronan,

on logging it’s always a good idea to have some data to back up thoughts and presumptions; like you say on high load / heat situations.. track days etc

it can also be a great tool for peace of mind, so once your comfortable with the oil results from tests; happy with the choice of oil you have made and you have data to back it up you can sleep easier if that makes sense.