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Old 04-22-2014, 01:46 PM   #1
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No need for IMS upgrade on 1998 base Boxster?

After reading and re-reading the various threads, it appears my 1998 base model Boxster (made 11/97 in Finland) with 73k miles has a double row engine, which is less prone to IMS failure (apparently less than 1%).

Is this correct? If so, I'll probably pass on the IMS upgrade.

Thanks in advance for your comments and insight.
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Old 04-22-2014, 02:13 PM   #2
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Well, i have also done loads or reading and re-reading as well. I have been to see a couple of Porsche specialists on the very matter and the last guy i spoke to i found very knowledgeable and basically the conversation lead to the overall design of the Boxster engine. My 986 is a 2004 2.7 car and has the 3 timing chains which i am told are an improvement from the previous 5 timing chains on, i think, the 2.5 cars. Anyways the IMS was intended to last the lifetime of the engine, which as we all know can and probably will fail prematurely. I was looking to upgrade my IMS, RMS and clutch all together mostly for peace of mind, but most of the specialist ive spoken to tell me even the upgraded bearings can still fail. i am told the oil fed bearings so far are the best option. As it is not intended to be replaced they recommend having the engine removed strip down and rebuilt with complete new IMS shaft and full seal kit. But that is about £4500.00 and then the bearing can still fail. Apparently to save money porsche made both cylinder heads the same , rather than on left hand and one right hand, thus the need for an intermediate shaft to drive the timing chain at each end of the engine.

my car has done 86k miles, 40k done by me in the last 5 years. I probably won't get an upgrade at the moment. its due for a service end of this month so i will have the oil thoroughly checked for debris then plan it from there.

i found some good info on the Porsche servicing, repairs, engine rebuilds, reconditioned wishbones and cars for sale - near Bolton, North West England. website and thats who the specialists i have spoken to have recommended for the engine rebuild. i know they are here in the UK but you may well find some useful info.

from what i can tell and read it is completely pot luck if and when it will fail. I try not to worry about it, but i still do.

sorry if i dragged on a bit but that is the info i have read and been told.

hope it helps

steve.
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Old 04-22-2014, 02:28 PM   #3
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Originally Posted by SvenskaPoika View Post
After reading and re-reading the various threads, it appears my 1998 base model Boxster (made 11/97 in Finland) with 73k miles has a double row engine, which is less prone to IMS failure (apparently less than 1%).

Is this correct? If so, I'll probably pass on the IMS upgrade.

Thanks in advance for your comments and insight.
All M96/97 share some level of potential for and IMS failure, and while the percentages vary and in some cases may be low, the consequences of the failure are usually catastrophic. You need to decide if you are willing to live with that risk.
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Old 04-22-2014, 02:46 PM   #4
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it's not really an "upgrade". That's the wrong way of looking at in my opinion.

It's more a refresh that happens to come with some key upgrades. Fact is a sealed bearing, even a dual row, will not last forever.

Given enough time under the wrong conditions, and a dual row bearing, like on 97-99 cars, will fail as well.

The inherent flawe in this bearing design is not addressed in any IMS bearing be it from the factory or the aftermarket, they all simply attempt address longevity, some very well others not all.
But at the end of the day oil contamination and oil starvation of the bearing still appear to be the root cause of these engine failures. Today we have some options available to us that insure that oil starvation is not a problem anymore (Direct Oil Feed lines) and other options remove the bearing altogether (the LNE Solution). But you're not getting either of these perks by leaving the factory bearing in there simply on account of it being a dual row bearing.... a bearing now pushing the 15-20 year mark.

so unless you know how the previous owner took care of the car it's a bit of mystery for any car if your IMS bearing is near its end or good to go.
If there's any doubt about this, the best policy is simply to put in a new one. After all a serviceable bearing should be replaced at some interval to avoid collateral damage.
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Old 04-22-2014, 02:51 PM   #5
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Well, i have also done loads or reading and re-reading as well. I have been to see a couple of Porsche specialists on the very matter and the last guy i spoke to i found very knowledgeable and basically the conversation lead to the overall design of the Boxster engine. My 986 is a 2004 2.7 car and has the 3 timing chains which i am told are an improvement from the previous 5 timing chains
I heard the complete opposite. Not a net improvement.
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Old 04-22-2014, 08:58 PM   #6
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my 98 that I pulled a couple days ago...

https://lh5.googleusercontent.com/-PocrH_Fd_QE/U1L0qR9Nt0I/AAAAAAAAiZ4/ins3vZZCybo/w576-h324-p-no/20140419_110526.mp4





Tomorrow if I remember I'll show you the 2001 I pulled a couple months ago. Also a dual roll.

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Old 04-22-2014, 09:05 PM   #7
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oh... by the way did I forget to mention that the 98 has a little over 256K miles on it???
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Old 04-22-2014, 11:48 PM   #8
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^ sorry what's on this annim visual? Is that a IMSB rocking because of chewed balls/races?

If it is indeed what I think it is, you just saved a boxster engine mate

sppoookky
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Old 04-23-2014, 12:03 AM   #9
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^ sorry what's on this annim visual? Is that a IMSB rocking because of chewed balls/races?

If it is indeed what I think it is, you just saved a boxster engine mate

sppoookky
Engine still running at 256k miles though.

Many people here would insist on changing the bearing regardless ( 3k, 30k, 70k).

Clearly the cars have the capacity to go a long time.
Failure is not always 'imminent'.

Depends on if you're the type to roll the dice ( I am).
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Old 04-23-2014, 02:01 AM   #10
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Originally Posted by M4SGK1986 View Post
Well, i have also done loads or reading and re-reading as well. I have been to see a couple of Porsche specialists on the very matter and the last guy i spoke to i found very knowledgeable and basically the conversation lead to the overall design of the Boxster engine. My 986 is a 2004 2.7 car and has the 3 timing chains which i am told are an improvement from the previous 5 timing chains on, i think, the 2.5 cars.
Not really, plus you have the weakest design IMS bearing as well.
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Old 04-23-2014, 06:02 AM   #11
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Apparently to save money porsche made both cylinder heads the same , rather than on left hand and one right hand, thus the need for an intermediate shaft to drive the timing chain at each end of the engine.
The intermediate shaft design also performs the 2:1 gear reduction from the crankshaft speed to the camshaft speed, thus lowering the velocity of the long chains going out to drive the cams by the same amount. This is a significant benefit.
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Old 04-23-2014, 08:53 AM   #12
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^ sorry what's on this annim visual? Is that a IMSB rocking because of chewed balls/races?

If it is indeed what I think it is, you just saved a boxster engine mate

sppoookky

Yep the bearing was just before the point of disintegration. Good thing I did not wait!!!


LOL





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Old 04-23-2014, 08:57 AM   #13
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For your situation, convention wisdom is change your IMS at your next clutch job...
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Old 04-23-2014, 10:04 AM   #14
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The issue with the OEM dual row IMSB is they take too long to progress through Stage 3 of the failure process. The stronger bearing is made stronger by having more components to share the loads, the issues is there's 2X the amount of wear components to shed material, contaminate the oil system and create massive collateral damages from foreign object debris. Since the dual row bearing will hold together longer the debris circulates longer.

Dual row IMSB failures are much more damaging to the remainder of the internally lubricated components. This damage is the most expensive to remedy, by far.

I pulled this dual row IMS bearing yesterday from a 9K mile 2000 Boxster.. Thats right, 9K miles and the low mileage and time spent sitting around has already compromised the seal. He is lucky that he decided to retrofit this one.

Can't wait to cut it apart!
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