Strange metallic grinding noise when engine in idle: 2006 997 C4

[JFP in PA]

Sorry to be the bearer of bad tidings, but this is they way we have always worked with the M96/97 engine cars.

[Boxman90]

Few additional questions though, cause I've read some of your contributions in other topics, like with stick-on magnets and so on, which indicate that there is always some tiny ferritic particles sloshing around, which can also pass through the oil filter. These are not a problem, then?

 

What size is 'too big' and would they not be caught by the oil filter?

[JFP in PA]

Yes, there is always some fine ferrous material in the system, usually smaller than 8-10 microns, which can actually pass through many oil filters (the OEM filter has a pore diameter of around 30 microns).  But that does not mean that they are benign, just slower in how they wear surfaces due to their size.  Use of magnets easily remove them and prevent any wear action.  Large particles are more pronounced in how they tear up surfaces like bearing shells or cam shafts, and therefore a bigger issue. 

[Boxman90]

I won't be liked for saying it, but to me it just doesn't add up, thinking about it critically from an engineering standpoint.

 

On the one hand, "any and all ferritic debris is bad and requires an engine rebuild because the 'grit' keeps circulating." At the same time, apparently "small ferritic debris that pass through the oil filter are not as much of a problem", as it doesn't disqualify an engine for a retrofit. Sure, the magnet is nice, but apparently it's not that big an issue if you don't have one. Then, if you had an IMS go, apparently the big grit is a 'huge problem', even though the oil filter fully catches these particles before the oil is sent to actual critical pressurized components. Grit won't 'circulate' through the engine as it will only meet the oil filter once. You'll catch it and even if some gets dislodged elsewhere and ends up in the sump, it'll be picked up by the filter before it's circulated.

 

I'm confused about the reasoning, it seems contradictory.

 

So after an IMS failure, cleaning as best as possible with the engine in the car, you'll have some remaining debris of which:

- The large particles and grit will be caught by the oil filter before going to critical engine parts. None of these will pass through.

- The fine particles that pass through the oil filter were not really that much of a problem anyway apparently, as it doesn't disqualify for a retrofit and is deemed 'normal wear'.

 

I don't see a solid, scientific reason why the engine cannot be fixed instead of rebuilt. Be it with a service interval on the IMSB. I've seen anecdotal evidence of 'people who blew their engine 75 miles after', but what's to say they never cleaned their oil system, didn't bother to replace their filter, or had a faulty bypass valve - this doesn't mean anything at all. I have yet to read a solid reason on how the debris can cause mayhem elsewhere.

 

Even if an IMSB went, with a fully properly working oil filter without bypass, there is no way for these debris to end up in any of the critical pressurized systems as far as I know. Is this wrong?

 

If i'm not, it comes down to how long a new IMSB can survive in the splash-oil that may have a small amount of leftover debris in the sump. Obviously, use one with seals in that case, not an open bearing. Obviously, flush the engine thoroughly with fresh oil after cleaning as best as possible with the oil pan off. Hell, if you'd fit the pressurized IMS solution, you shouldn't have to worry about the sump oil anyway, since it gets fresh fully filtered oil. If I'm wrong, what brainfart am I making here?

 

I fully understand that taking it apart and cleaning everything is the absolute best option. From an engineering standpoint, I simply don't see how it could ever be the ONLY option.

[JFP in PA]

9 hours ago, Boxman90 said:

I won't be liked for saying it, but to me it just doesn't add up, thinking about it critically from an engineering standpoint.

 

On the one hand, "any and all ferritic debris is bad and requires an engine rebuild because the 'grit' keeps circulating." At the same time, apparently "small ferritic debris that pass through the oil filter are not as much of a problem", as it doesn't disqualify an engine for a retrofit. Sure, the magnet is nice, but apparently it's not that big an issue if you don't have one. Then, if you had an IMS go, apparently the big grit is a 'huge problem', even though the oil filter fully catches these particles before the oil is sent to actual critical pressurized components. Grit won't 'circulate' through the engine as it will only meet the oil filter once. You'll catch it and even if some gets dislodged elsewhere and ends up in the sump, it'll be picked up by the filter before it's circulated.

 

I'm confused about the reasoning, it seems contradictory.

 

So after an IMS failure, cleaning as best as possible with the engine in the car, you'll have some remaining debris of which:

- The large particles and grit will be caught by the oil filter before going to critical engine parts. None of these will pass through.

- The fine particles that pass through the oil filter were not really that much of a problem anyway apparently, as it doesn't disqualify for a retrofit and is deemed 'normal wear'.

 

I don't see a solid, scientific reason why the engine cannot be fixed instead of rebuilt. Be it with a service interval on the IMSB. I've seen anecdotal evidence of 'people who blew their engine 75 miles after', but what's to say they never cleaned their oil system, didn't bother to replace their filter, or had a faulty bypass valve - this doesn't mean anything at all. I have yet to read a solid reason on how the debris can cause mayhem elsewhere.

 

Even if an IMSB went, with a fully properly working oil filter without bypass, there is no way for these debris to end up in any of the critical pressurized systems as far as I know. Is this wrong?

 

If i'm not, it comes down to how long a new IMSB can survive in the splash-oil that may have a small amount of leftover debris in the sump. Obviously, use one with seals in that case, not an open bearing. Obviously, flush the engine thoroughly with fresh oil after cleaning as best as possible with the oil pan off. Hell, if you'd fit the pressurized IMS solution, you shouldn't have to worry about the sump oil anyway, since it gets fresh fully filtered oil. If I'm wrong, what brainfart am I making here?

 

I fully understand that taking it apart and cleaning everything is the absolute best option. From an engineering standpoint, I simply don't see how it could ever be the ONLY option.

 

You are overlooking one major flaw in your argument:  Most of these cars do not have full flow filters, and the factory bypass system is famous for jamming open and allowing all the debris to circulate; large, small, and everywhere in between.  And even on cars with full flow filters, they are not a guarantee that debris won't get past the filter due to oil splash within the engine; we have pulled apart engines using full flow filters that were packed solid with metal, but still found more grit inside the cam covers and the oil pump,, which according to your thought train should be impossible, but there it was.  Some of the cars equipped with full flow filters appeared to literally killed the engine's due to oil starvation because the filters were packed solid with metal and not allowing enough oil to get by.  And adding a full flow filter after the debris is already everywhere in the engine will not stop the grit from doing damage on its way back to the sump, it will only collect the results.

 

Over the years, shops have tried to develop an alternative method to flush out the debris without taking the engine apart; unfortunately none of them have worked out, leaving us with disassembly or replacement as the only viable options.  Even commonly used "hot tanks" do not clean out this stuff, it requires an ultra sonic bath large enough to put the cases in, which most machine shops do not have as they are very expensive aircraft repair items.

 

At the end of the day you asked for an opinion, which we gave you.  It is the same opinion I have given customers numerous times, and one I stand by.  But that does not mean you have to follow it.  In the end, it is your car, and your money; so if you want to continue to run it, that is your call.  Who knows, perhaps you might get lucky and be one of the very few to pull this off.  But if it were a customer car in my shop, I would not do it as experience has shown that the odds are very much against it coming out in your favor.

[Boxman90]

I know, and I thank you for the willingness to discuss.

 

I wouldn't say I overlooked it as I specifically did mention "without a faulty bypass valve".

Assuming a clean, full-flow oil filter, which components are at risk for getting damaged by grit as it's on the way back to the sump? I'm still figuring out the exact oil routes in this block, but I suppose it cannot reach the main- and rod-bearings, right?

[JFP in PA]

[Boxman90]

That's very helpful, thanks a bunch ?

[JFP in PA]

Loose grit inside the engine can still get in between the rod journals and the crank assembly and start tearing things up from there.

[Boxman90]

Well.. How? I've read that sentence so many times but the 'how' is always missing.

[JFP in PA]

4 hours ago, Boxman90 said:

Well.. How? I've read that sentence so many times but the 'how' is always missing.

 

Simple: Gravity will do it.  Even if the grit dose not get pumped around with the oil, there is a tremendous amount of slosh and windage in these engine's. This is one of the reasons they are so heavily baffled and contain multiple air oil separators in the sump.  Grit come off a failing IMS bearing, or any other failing component, drops into the sump and gets sloshed or other wise whipped up into the crank carrier, falling in between the rod and crank, or worse yet into the thrust bearings for the crank, where they start grinding away.

 

If the car had the factory oil filter installed, most of which have questionable by pass valves, and the process is much more direct:  The grit simply blows by the filter, chewing up the oil pump gears, and is pressure fed directly onto rod and main journals.  While this second process comes to an end much quicker, both end up in the same place.

[Boxman90]

In all my posts I'm assuming the use of a full-flow non-bypass filter. I've disassembled the oil case, the oil in the sump doesn't reach the crank by a long shot. There's only a small window to the crank anyway. The splash coming from the sump will be minimal at best. But even then, oil circulates at a pretty serious volume. The volume in the sump will not be there for very long before all that oil has been worked through the filter. In the end, the vast vast majority of all grit will reach the filter. Your story only holds up if the oil in the sump is permanently contaminated and does not get rid of its grit. It will, cause it will be sucked up by the oil pump and pushed through the filter.

 

 

My issue is this: When an LN Full-flow adaptor needs to be sold, the sales pitch is "this will filter all of the debris protecting your engine, you absolutely need this if you want to be certain your journal bearings receive clean oil at all times!" Then, whenever any amount of grit is in the engine, the sales pitch targets a full rebuild and the tune changes to "yeah this will get anywhere nothing will help, your engine needs to be taken apart completely".

 

It's either-or, not and-and. You can't have the LN adaptor both filter grit and not filter grit depending on the sales pitch that needs to be thrown. Either it works, or it doesn't.

There are two options, really.

1) The filter works, protects your engine from grit, saves your bearings.
2) Any amount of grit (so even a few pieces) destroys the bearings, the existence of spin-on adaptor + fullflow filter is moot.

 

So which is it? It obviously can't be both.

[JFP in PA]

Does the LN full flow design filter all the oil?  The answer is yes, and very effectively as it uses a filter with significantly smaller media pore diameters than the stock filter..  But let me ask you a question:  Did the IMS bearing fail while the engine was running the LN spin on, or did it still have the OEM cartridge filter?  If it was the latter, then the engine oil passages are already full of grit, which is going to get to the bearings regardless of which filter is used, and adding the LN filter after the fact will not change that.  The LN filter "sales pitch" as you state it was meant to apply to a healthy engine, not one that has already suffered IMS damage.  And if you don't believe me on that, I would suggest you drop LN an email and ask their opinion on what you are trying to do. 

 

 

[Boxman90]

That's a questionable catch-all conclusion, really only works if your bypass failed which is only the case in a small percentage of cars. The cartridge filter is inherently full-flow in design too. Simply has a potential for the bypass valve to fail, but as long as it's doing its job properly you really cannot conclude that broken IMS always equals grit in pressurized oil passages. Unless IMS damage also always destroys your bypass valve?. The spin-on just ensures the bypass failure mode is removed. But really, if you have a faulty bypass valve and you're constantly running unfiltered oil - with or without grit -, the engine shouldn't even make it past 10k km from the increased overall wear, everything will grenade.

 

I have mailed with the LN guy, and they tried to charge me 350 bucks an hour to even mail with the guy, rofl. He answered 0 of my questions, probably because I said I'm not in the US so i'm not a potential customer. I'm not even joking, I wish I were.

[JFP in PA]

4 hours ago, Boxman90 said:

That's a questionable catch-all conclusion, really only works if your bypass failed which is only the case in a small percentage of cars. The cartridge filter is inherently full-flow in design too. Simply has a potential for the bypass valve to fail, but as long as it's doing its job properly you really cannot conclude that broken IMS always equals grit in pressurized oil passages. Unless IMS damage also always destroys your bypass valve?. The spin-on just ensures the bypass failure mode is removed. But really, if you have a faulty bypass valve and you're constantly running unfiltered oil - with or without grit -, the engine shouldn't even make it past 10k km from the increased overall wear, everything will grenade.

 

I have mailed with the LN guy, and they tried to charge me 350 bucks an hour to even mail with the guy, rofl. He answered 0 of my questions, probably because I said I'm not in the US so i'm not a potential customer. I'm not even joking, I wish I were.

 

Actually, the OEM bypass issue is much worse than you think.  Somewhere between 40-60% of the cars we see with the factory set up have a by pass that is anywhere from leaking to literally wide open, bypassing the filter completely on engines without other mechanical issues. The valve, which is located in the bottom of the plastic filter canister is a very shaky design that is quite often overlooked when the oil is changed, primarily because of its location which makes checking it problematic.  The factory filter design also has had issues with the glued on paper end caps becoming unglued during use, which causes anther bypass route for the oil.  This combination of factors has helped make spin on full flow aftermarkets systems very popular modifications in North America.  And as Porsche in their infinite parts wisdom only sell the valve with the cannister, few are ever recognized much less replaced, so I would think your estimate of not making it more than 10K miles is more than a bit overstated, and also speaks to the inherent durability of these engines.

 

I really don't know what to say about your experience with LN; many posters here have contacted them over the years with a variety of questions and have always gotten answers without any charge.  This is either something new, or perhaps you are correct about international inquiries.

[ttocs]

I hope I'm not out of line with this, but you might try Pedro's Garage. Pedro seems to be pretty accessible and he's got IMS products. 

[Boxman90]

Just an update, I've replaced the bearing with a generic sealed dual-row bearing after thoroughly cleaning with magnets, rags and fresh oil. I was as meticulous as can be, replaced the internal swirl pots too. Car has been going strong for 1000km now.

 

Total cost excluding oil and was ~150$.

Edited June 16, 2018 by Boxman90

[ttocs]

I wish happy miles upon you! Please keep us updated from time to time.

 

Will you be doing a few low mile oil changes and analysis to provide a baseline and tracking future progress?

[Boxman90]

No oil analysis, but 2000km since my last post and a good trip on the German Autobahn it's still running absolutely fine. After replacing the filter a few times, the oil was changed one last time 500km ago, to Mobil 1 5w50. Checked the oil filter yesterday when doing the IMS chain tensioner, and it was absolutely spotless. Not a single piece of metal or plastic.

[Jager]

Did you replace the IMS bearing by yourself?

[Boxman90]

Yep. Fun job, tbh. 

[Jager]

I have replaced two IMS bearings on 996/986 motors but I have not done a 997. Dropping the motor and splitting the case is much more involved ... Any tips?

[Boxman90]

Oh no, mine was a 996. The vid in the OP is not mine. Stumbled upon it when researching the sound mine made.