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Last fall I had a major water pump failure that resulted in pieces of the plastic impeller getting ground off and circulated throughout the engine, so after consulting with several people it became clear that I needed to have the entire coolant system flushed and have the cylinder heads removed for a full cleaning (otherwise the heads would have eventually developed hot spots and cracked). I originally planned to send the car off to Flat6, but they were backed up for three months and the local PCA members said we have a very highly qualified 996/997 specialist in our area (doing 996 and 997 race engine work since 99, and has never had a single one come apart), so he's doing the work.
Since it has 75k miles and has sat in storage several times, sometimes going many months in a row without being driven, I agreed to do a full teardown with all new bearings and several other bits (new chains, IMS bearing, chain tensioners, AOS, etc. etc.). The engine is currently disassembled and it's mostly great news. With the exception of the IMS bearing, all internals are in excellent condition! The IMS bearing was absolutely on its last leg, and I am actually very lucky that the water pump failed when it did, or things would be much worse by now. The builder said that it's the worst condition early-996 double-row IMS bearing he's ever seen that hadn't failed, and that it could have potentially been a few starts away from catastrophic failure, and invited me over to take a look. The videos below show the IMS shaft with the bearing still installed, first with the cover still installed, then with the cover removed with full view of the bearing. I also have a pic of the busted ball cage that fell out after we popped the seal off.
The only reason it lasted that long is because its a dual row bearing... But... If you look hard enough you'll find collateral damage that came from the wear debris suspending into the oil. This is usually seen on the cam journals in the cylinder heads, and their caps.
The big issue with a dual row bearing is it can take too long to fail, and it has twice as many wear components to generate debris than a single row. Regardless, that bearing was at Stage 3 failure. It had failed, it just hadn't came apart yet (stage 4).
The only reason it lasted that long is because its a dual row bearing... But... If you look hard enough you'll find collateral damage that came from the wear debris suspending into the oil. This is usually seen on the cam journals in the cylinder heads, and their caps.
Given that the seals appear to have stayed in place, would it really have allowed enough debris out to cause significant collateral damage? It seems like anything that could have escaped would have been of a size and amount that I wouldn't expect to be able to cause significant damage.
Given how little flow the seals seem to let through, it would seem to reason that the majority of the debris would have stayed in the bearing and hastened it's demise. Is there more flow than I'm giving it credit for at operating pressure?
Given that the seals appear to have stayed in place, would it really have allowed enough debris out to cause significant collateral damage? It seems like anything that could have escaped would have been of a size and amount that I wouldn't expect to be able to cause significant damage.
Given how little flow the seals seem to let through, it would seem to reason that the majority of the debris would have stayed in the bearing and hastened it's demise. Is there more flow than I'm giving it credit for at operating pressure?
Absolutely!!!!
I do t k ow why everyone discounts the tiniest of particles of this material that are super hard. I am not worried about chunks doing damage, they stay in the sump. I am worried about the tiny particles that are light, and easily suspend themselves in the oil. This allows the oil to deliver them to every internal part of the engine, and start taking parts out one by one.
The smallest of particles are the ones that are the most damaging, and they can easily escape from a failing bearing that still has seals in place. There's so much splash lubrication of engine oil in the region that it washes the debris right back to the sump.
This is why it's imperative to carry out all IMS Retrofit work prior to a bearing failing, and certainly before it reaches the point of this one. Once the bearing begins to fail it should be disqualified from retrofit.
With the bearing at stage 3 failure damage to the IMS shaft assembly may have already occurred. The rear most drive sprocket is lightly staged with 1/4" of engagement, so the vibration and trauma of the bearing failing can create runout on this sprocket and that can make the drive literally fall off later down the road (MOF 24), or it can have enough runout to compromise the drive chain (especially the early duplex units like this one in the video).
I do t k ow why everyone discounts the tiniest of particles of this material that are super hard. I am not worried about chunks doing damage, they stay in the sump. I am worried about the tiny particles that are light, and easily suspend themselves in the oil. This allows the oil to deliver them to every internal part of the engine, and start taking parts out one by one.
The smallest of particles are the ones that are the most damaging, and they can easily escape from a failing bearing that still has seals in place. There's so much splash lubrication of engine oil in the region that it washes the debris right back to the sump.
This is why it's imperative to carry out all IMS Retrofit work prior to a bearing failing, and certainly before it reaches the point of this one. Once the bearing begins to fail it should be disqualified from retrofit.
With the bearing at stage 3 failure damage to the IMS shaft assembly may have already occurred. The rear most drive sprocket is lightly staged with 1/4" of engagement, so the vibration and trauma of the bearing failing can create runout on this sprocket and that can make the drive literally fall off later down the road (MOF 24), or it can have enough runout to compromise the drive chain (especially the early duplex units like this one in the video).
Worry more about the damage that can't be seen.
So in your opinion this car would not qualify for the IMS Solution at your shop? If you had this car what would you be recommending?
In an example like this with intact seals, would you expect there been enough debris out in the oil that a magnetic plug or examining the filter (sans microscope) would have given enough sign to be concerned?
Originally Posted by Flat6 Innovations
With the bearing at stage 3 failure damage to the IMS shaft assembly may have already occurred. The rear most drive sprocket is lightly staged with 1/4" of engagement, so the vibration and trauma of the bearing failing can create runout on this sprocket and that can make the drive literally fall off later down the road (MOF 24), or it can have enough runout to compromise the drive chain (especially the early duplex units like this one in the video).
Yeah I was wondering about what impact the amount of play shown in the video could be having to the IMS itself and the parts it drives (and is driven by).
So in your opinion this car would not qualify for the IMS Solution at your shop? If you had this car what would you be recommending?
I believe from past discussions that he is saying he would not have done (and no certified installer should be doing it either) just the swap. He would have required the motor to be torn down (like it already has been) and rebuilt to address any of the collateral issues.
I believe from past discussions that he is saying he would not have done (and no certified installer should be doing it either) just the swap. He would have required the motor to be torn down (like it already has been) and rebuilt to address any of the collateral issues.
This bearing has failed! It just hasn't come apart yet.
The Code Of Conduct that we created for all Certified Installers is followed here, as we lead by example. There is no way that an engine with a bearing in this condition would pass the 11 step checklist that is required for an engine to be qualified for retrofit.
Doing these things and taking this seriously is how we have almost 550 IMS Retrofits under our belts with zero post- procedure failures or complications.
At the point that the bearing has failed, the process is no longer preventative, it becomes reactive. Complete disassembly and ultrasonic cleaning of every part is the only way to remove this debris.
I'd be interested to learn from the OPs mech what was left in the sump when the oil was drained and a picture of the pleats of the oil filter. Also a pic or two of the cam lobes?
This pretty much makes my decision to add a remote particulate oil filter to my engine mandatory.
This is the key sentence here for me: "Since it has 75k miles and has sat in storage several times, sometimes going many months in a row without being driven"
Drive it often like you stole it, change the oil frequently and the factory double rows will be fine. I truly believe that. Glad your engine was saved.
This is the key sentence here for me: "Since it has 75k miles and has sat in storage several times, sometimes going many months in a row without being driven" Drive it often like you stole it, change the oil frequently and the factory double rows will be fine. I truly believe that. Glad your engine was saved.
That's not a 100% cure, but well used cars seem to have a lower frequency.
Besides even if it does go you got to have a blast getting to that point
01-22-2016, 12:39 AM
IMS Bearing ALMOST failed
