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What actually, IS the extent of the damage when the IMS goes?

I'm asking because I'm looking at a relatively clean, 2001 base model (2.7) with 80K miles.

The PO thinks he has the bearing failure because he found metal shavings in the filter and heard a noise before he parked the car. I think he's straight-up - and the car is being sold at a price that even makes engine replacement (used) possible...

The engine turns over, but the battery was completely dead (had to swap the battery out). The car does NOT start - does not even try to catch. It SOUNDS like it has compression. I'm actually inclined to believe that the fuel pump or the CPS may be out - but I haven't had time or access to the car yet (hopefully in about a week or so). I have dealt with a 454 Chevy that busted a timing chain and so I'm well aware of what happens when a piston hits a valve (or 4) - but in that truck you could hear the difference in the way the engine turned over - no compression - the engine just spun.

I know I should do a compression check (that will definitely give me the answer) - but when the IMS goes, and the timing jumps, is it really a grenade just taking out everything, or does the rotating assemby lock up, or does it just bend the crap out of valves? If it jumps just one tooth, will that keep the engine from starting/running, and still not run into interference issues? Theres lots out there on these things breaking, or people being AFRAID of them breaking - but I haven't seen any good descriptions of EXACTLY what the end result was, other than "the engine is toast"

Thanks all!!!!
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Last edited by kuehjo; 09-27-2012 at 09:10 PM..
Old 09-27-2012, 08:27 PM
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When the IMS fails, typically the engine jumps time and you get piston to valve contact, resulting in severe cylinder head and piston damage (hence the lack of compression). Besides this, usually the entire engine if filled with a very abrasive metal grit that chews up everything, which is why LN Engineering has always said that once the IMS starts to fail, but has not gotten to the point that the timing has jumped, you cannot just do the upgrade because all of the grit debris in the engine is going to kill it anyway; it is just a matter of time.

Dump the oil into a pan, and pull the filter and cut it open; if both are full of metal, the engine is toast and either needs a full rebuild or replacement.

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Old 09-28-2012, 05:27 AM
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Holy crap! Nothing in that engine is salvageable.

Nick
Old 09-28-2012, 06:34 AM
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Originally Posted by white out View Post
Holy crap! Nothing in that engine is salvageable.

Nick
Basically, you are correct. The case may be re sleeved with Nickies and put back into service.

Not cheap, but it is avoidable.............
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Angry IMS Failure

Holy moly! IMS failure is like a massive heart attack in humans!
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They don't always go this wrong, but many do. At a minimum, once the engine jumps time, you are going to have bent or broken valves and the associated damage. We have caught engines in the early stages, when there is just the debris from the IMS alone, and for the most part, they could not be saved either due to the potential for the girt damage.



That said, you need to step back and recognize that it can be avoided, and the potential downsides for cheaping out on trying to prevent it.
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Thats part of the answer I am looking for - those pictures are worth a thousand words!!

So the issues are two-fold:
1.) timing
2.) metal grit (bearing debris)

The proper LONG-TERM answer to #2 is a rebuild and a good cleaning

But regarding #1 - so the timing can skip as little as a tooth, or it can be catastrophic?

Does the engine tend to lock up? or it MAY, but it may NOT (depending on what broke or got bent)?

I'm looking forward to putting my hands on the car and pulling the old IMS - at 80K miles I would be thinking of replacing it ANYWAY - and this would be a great time to address the RMS at the same time. There is no guarantee that this one has gone bad - the PO is concerned that it MIGHT have it - but I don't think that he does a lot of his own maintenance beyond changing the oil. So I'm a little reluctant to accept his diagnosis without looking at it closely. And I won't know until I either start the car (which I am understandably reluctant to do if the issue POTENTIALLY exists) or pull the old IMS out and get a better look at it. The kind of noise he describes could be the IMS, a wheel bearing, the clutch, brakes (and probably a number of other things)... He says it does NOT change linearly with engine rpms - that makes me wonder, as I would expect IMS bearing noise to cycle with rpms.

I will start by checking the timing, emptying the oil, cutting open the filter, checking the fuel pump and relay, and possibly dropping the pan, in addition to PLANNING to replace the IMS - if evidence begins to mount that it has indeed failed, then I will do a rebuild or replace. The car is still a clean car, and the price is right
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Last edited by kuehjo; 09-28-2012 at 12:20 PM..
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These are true "interference" motors, so jumping time is a major problem. You can even get one of these engines with the correct timing into trouble by just rotating it backwards by hand. The limit of cam deviation values (how far they can be off the correct timing as read by a PIWIS/PST II/Durametric system) is -/+6 degrees, one tooth on the drive gears is more than twice that amount.

And, yes they will turn over with holes in the pistions, etc. Rotation is only stopped when debris in the cylinders or crank carrier jams the sytem.
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Old 09-28-2012, 12:56 PM
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I've been considering your remarks concerning rebuilding and replacing. Please dont take my following comments as critical - I just have a different point of view - and I am open to being corrected if I am mistaken.

I believe that many Porsche owners have the financial means to proceed with a rebuild or replace - but I know some are struggling to financially support their affection for their machine.

NO-ONE wants any kind of debris in their engine or contaminating their oil - but the entire point of the oil pickup screen and filter is to REMOVE these kinds of contaminants before they can damage the rotating assembly.

That said, if the bearing is failing, but the timing has not jumped teeth, in most cases it would seem to me that these engines should be salvageable. The bearing should be replaced, the oil and filter should be changed, and perhaps some version of a flush or a quick oil change (maybe at 100 miles) should be adequate to put these engines back in serviceable condition?

I'm not a Porsche mechanic so feel free to take what I say with a grain of salt, nor do I mean to cause any offense - just offering an alternate perspective - and I might be wrong.... I'm decent at working on my own cars, and I have rebuilt a 928 engine. It just sometimes seems to me that there is the mystique built up about Porsche engineering that is a little over the top - these machines are still just machines. The machine work is just machine work, and the specs are measured as they are in any other engine rebuild. I think Jake Raby's course in engine rebuilding would be immensely interesting and enlightening, but mandatory? Maybe - but maybe not...
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Old 09-30-2012, 02:14 AM
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Quote:
Originally Posted by kuehjo View Post
I've been considering your remarks concerning rebuilding and replacing. Please dont take my following comments as critical - I just have a different point of view - and I am open to being corrected if I am mistaken.

I believe that many Porsche owners have the financial means to proceed with a rebuild or replace - but I know some are struggling to financially support their affection for their machine.

NO-ONE wants any kind of debris in their engine or contaminating their oil - but the entire point of the oil pickup screen and filter is to REMOVE these kinds of contaminants before they can damage the rotating assembly.

That said, if the bearing is failing, but the timing has not jumped teeth, in most cases it would seem to me that these engines should be salvageable. The bearing should be replaced, the oil and filter should be changed, and perhaps some version of a flush or a quick oil change (maybe at 100 miles) should be adequate to put these engines back in serviceable condition?

I'm not a Porsche mechanic so feel free to take what I say with a grain of salt, nor do I mean to cause any offense - just offering an alternate perspective - and I might be wrong.... I'm decent at working on my own cars, and I have rebuilt a 928 engine. It just sometimes seems to me that there is the mystique built up about Porsche engineering that is a little over the top - these machines are still just machines. The machine work is just machine work, and the specs are measured as they are in any other engine rebuild. I think Jake Raby's course in engine rebuilding would be immensely interesting and enlightening, but mandatory? Maybe - but maybe not...
This is why I have installed the IMS Guardian, the cheapest form of insurance against a major blowout of the IMS. Assuming it does it's job, it will detect sufficient metal in the engine oil
so I can shut the motor off before major damage is incurred.
Old 09-30-2012, 05:28 AM
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Quote:
Originally Posted by kuehjo View Post
I've been considering your remarks concerning rebuilding and replacing. Please dont take my following comments as critical - I just have a different point of view - and I am open to being corrected if I am mistaken.

I believe that many Porsche owners have the financial means to proceed with a rebuild or replace - but I know some are struggling to financially support their affection for their machine.

NO-ONE wants any kind of debris in their engine or contaminating their oil - but the entire point of the oil pickup screen and filter is to REMOVE these kinds of contaminants before they can damage the rotating assembly.

That said, if the bearing is failing, but the timing has not jumped teeth, in most cases it would seem to me that these engines should be salvageable. The bearing should be replaced, the oil and filter should be changed, and perhaps some version of a flush or a quick oil change (maybe at 100 miles) should be adequate to put these engines back in serviceable condition?

I'm not a Porsche mechanic so feel free to take what I say with a grain of salt, nor do I mean to cause any offense - just offering an alternate perspective - and I might be wrong.... I'm decent at working on my own cars, and I have rebuilt a 928 engine. It just sometimes seems to me that there is the mystique built up about Porsche engineering that is a little over the top - these machines are still just machines. The machine work is just machine work, and the specs are measured as they are in any other engine rebuild. I think Jake Raby's course in engine rebuilding would be immensely interesting and enlightening, but mandatory? Maybe - but maybe not...
The flaw in your argument about the problem with the grit in the sump is that you are not taking into account how the oil flows in these engines; if you do not get every bit of the debris out of the engine, two engine components are at direct risk: The oil pump assembly and the replacement LN IMS bearing. .

The screen at the bottom of the oil pickup is far too coarse in opening size to even slow down most of the grit, so it gets sucked into the oil pump (look at an oil system schematic for the M96/97 and you will see that the oil goes to the pump first, then to the filter). Because the pump uses very closely meshing steel gears to pump the oil, the grit can either grind away at the gears, or even totally jam them, snapping the already fragile oil pump drive rod, ending any oil pressure. Even if it does not jam the pump, it will abrade the gears significantly (they end up looking like the surface of the moon), reducing the pump’s ability to function. The grit can also jam the pump’s pressure by-pass valve assembly in the open position, further reducing or even ending any oil getting to the bearing surfaces of the crank and rods.

If the grit gets into the new IMS bearing, it will chew it to Hell, just like the oil pump, and it will fail. The rear IMS bearing is splash lubricated by oil from the sump, if that oil still contains debris; it is going to abrade the ceramic balls of the IMS until the inevitable happens. Of the handful of published LN bearing failures, several have been of this type, which is why LN (and Jake Raby) have remained adamant about not replacing the IMS bearing once grit is found in the sump.
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Old 09-30-2012, 07:24 AM
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Plus, the grit will plug the oil filter itself and cause the filter bypass to open and that will direct line grit to the crank and bearings. Once the bearing is toast its over.
If your seal is still on the bearing, you might have a fighting chance, but if the grit is in the pan.... your done.
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Thank you for taking my comments in the manner I intended them - that was exactly the response I was hoping for.

Point taken on the oil pump.

I alsp appreciate the point on plugging the filter and opening the bypass valve - although that has to be a LOT of crud to plug the filter enough to open the bypass valve.

And good point on the LN IMS bearing because it IS splash lubricated. But the OEM style bearing was not, so I could see where some might still argue the other way.

All that said, I find myself leaning more toward rebuild/replace - but i appreciate the discussion - its been educational!
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Old 10-01-2012, 11:15 AM
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Don't do it!!!!

My advise to you is based on my being 54 years old and buying plenty of fixer uppers along the way. You would be far better off to avoid this bargain however tempting it might be and instead focus on putting all your money into buying the best possible car you can that has never had a major problem. That said you will still be in the boat I am in now with a car with the original ims bearing.
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My advise to you is based on my being 54 years old and buying plenty of fixer uppers along the way. You would be far better off to avoid this bargain however tempting it might be and instead focus on putting all your money into buying the best possible car you can that has never had a major problem. That said you will still be in the boat I am in now with a car with the original ims bearing.
LOL!!

I find myself smiling because I know EXACTLY what you're saying - the 928 guys like to say that a $5000 car is still $5000 away from being a $5000 car.

I've bought plenty of fixer-uppers too - and rarely have I "made " money (I don't buy to flip - I buy to enjoy). But the process can be fun.

This one I might buy just because rebuilding a Boxster engine appeals to me - if I have to, I don't mind, and again - the opening price is low enough to allow me to do this. And of course, I have no guarantee what the actual problems are - so I'm going in expecting the worst.

All that said - you're absolutely right - the best bet is almost always to spend as much as you can afford - you'll likely be happiest in the long run
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Old 10-01-2012, 01:53 PM
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Ahhhh, the sirens song of a fixer upper!!! The 928 guys are of course right, but why confuse us with the facts. I have rarely come out on top from a $ point of view when I go this way. Just because you can doesnt mean you should. You have to be able to buy a car for very short money to make it worthwhile. My own formula or guideline, which I sometimes follow, is as follows. Purchase price of car + known parts + labor costs = 1/2 fair market value of the finished project. The difference will be eroded by the inevitable surprises and the rest is your reward for taking the risk. Applying this to my most recent project, a Boxster, I am at even money so , I cant even follow my own advise, but I usre like the car a lot, Good luck!
Old 10-02-2012, 08:29 AM
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Absolutely!

But then too, one could argue that to spend $60K (or more) on a brand new automobile is a losing proposition from the moment you drive off the dealer lot...

So how much do you value your enjoyment of driving? Or repairing? Is the challenge exciting?

I'm driving my 928 daily - and its only a 72,000 mile car now - but it is over 30 years old and so DEPENDING on it for daily use DOES start to get a little sketchy... But its a ton of fun!!!
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