Dispeling M96 engine rumors

[Jake Raby]

First, the intermediate shaft. This is NOT a hoax. Most of the engines that we have removed from cars have been caused by failure of the IMS bearing. There are several versions of the bearing that have been used across the production run of these engines. The early cars had a dual row bearing, which has proven to be fairly reliable. Then can the smaller single row bearing. This is where we have seen most of the failures

I concur with these statements..

. Replacing this bearing is not a complex job, and could be completed by any competent tech, with barely any additional labor while doing a clutch.

Using the procedures that LN Engineering and I have developed and continued to enhance many DIY owners have done the IMSR successfully. In fact the only instance we've had was when a 30 year Veteran decided to do the job his way without listening to our directives. Imagine that.

Second, clutches. Whoever says that these cars are due for a clutch by 30K is sorely mistaken. It all depends on the type of use the car gets and how its driven. We've seen plenty of client cars make it to 100k on the original clutch, and we've also seen some go bad by 30k.

So if some have gone bad by 30k that backs up the statements we've made that at that point wear can be significant, correct? I never made blanket statements about wear limits and service life- I don't do that.

Whenever doing a clutch, you need to replace the flywheel, so the notion of changing the clutch before it damages the flywheel is a moot point, as you're supposed to replace it anyway.

Why do you need to replace the flywheel?

If it's not slipping, keep driving it.

BUT what IF you want to do an IMSR and have the parts accessible to facilitate the procedures and you are at 1/2 life already on the disc and pressure plate, but the flywheel specs out good. Do you bolt it back together half worn out of spend the money and save the labor that would be due imminently?? I know what I'd do and what I've done.

Third, oil. While the factory endorses Mobil 1, there are better oils out there. Mobil 1 is not the product that it once was. At my dealership, we still fill with Mobil 1, but I don't run it in my personal cars.

I couldn't concur more..

Fourth, lifters. Whoever says that these cars all need lifters replaced by 60K must be smoking something really good!

Thats me. Don't slap me in the face and don't insinuate that my statements aren't true or have been exaggerated. I don't challenge your integrity, don't challenge mine.

If this were true, any M96 powered car over 60K would be considerably down on power.

And a significant chunk are. Its also not just power, but most every car that we see with low fuel economy also has failed lifters. I recently had a car show up here with 22 of 24 lifters bad, after our work the MPG jumped up 5 MPG, but the power didn't change more than 1HP and 1.5% average torque.

I have seen several client's cars dyno'd with varying mileage, and some of the highest mileage cars have put down the most power!

I dyno EVERY car that rolls into our facility, most of them I do for free to grow our data base. I have seen some high mileage engines make huge power as well, one of which had all 24 lifters bad when I disassembled it to be used as a base for a 3.8 big bore!

Also, keep in mind that if a car had failing lifters, it would be throwing codes.

Nope.. Just like they don't throw codes when the IMS drive sprocket for bank 4-6 slips on the IMS tube by as much as 5-7 degrees retarding the cam timing! The ECu doesn't measure valve lift or events, the last sample point it has is the cam sensor which is upstream of the lifters. The ECU can't tell that the valve events have changed due to lifter degradation, a cam position sensor won't tell that. If a code was ever thrown it would be due to the inefficiency and uneven combustion sampled by the O2 sensors if anything.

The engine we saw that had 22 of 24 lifters bad had no CEL illuminated.

We have put lifters in ONE car, and did so after it started experiencing drivability problems and throwing codes at 110K.

If you tore into more engines and etc you'd see just how many have bad lifters.

Also, I'd like to point out that were there any truth to this, all of the "evil dealers" would be pushing this service as it would bring in considerable revenue on the service side.

No, because that work is too "heavy" for the majority of dealers to carry out.. The last Dealer tech that I had here came from Brumos Porsche.. His first day here he did a lifter job, but didn't know how to do it because in the 5 years he worked there he had NEVER done it!

Fifth, head cracks. Some of these heads do crack. It is mostly limited to 3.2/ 3.4 heads, but we have also seen a few cracked heads on 2.5 and 2.7 engines. While they could probably be fixed, with potentially questionable reliability, by a head shop, at the dealer, we replace them with new.

I concur with the heads that you mentioned cracking the most... I will say that we have created repairs and upgrades for the crack prone areas that can save a head.

De to the variance I have measured with OE combustion chamber volumes to that of the new castings I'd never swap just one new head onto an existing engine. I have seen a variance of 1.5-3.5ccs differential in the castings and thats enough to create combustion imbalance thats significant between the opposing banks of cylinders.

The crack repair is extensive and isn't just welding up the crack. Thats why the head is stronger in the repaired area than it was previously. The first heads we repaired were purposely overheated and we tried to force a failure during the initial testing, those heads are still in service.

Sixth, cylinder wall failures. This has largely become a problem of the past. Most experienced on 2.5 and 3.4 engines, we haven't seen a "D Chunk" failure in quite a while.

I still get a call every now and then with this mode of failure, BUT they are limited to the '99 cars.

Overall, the M96 is a pretty good engine, with a few shortcomings. The IMS being probably the biggest. I see that the aftermarket has made upgraded IMS tensioner blades and oil pump drives, and I guess if you're building a motor the couple hundred dollars this adds could be considered peace of mind, though we haven't seen any of those parts fail at our dealership.

Actually you have probably seen an IMS tensioner paddle failure, but it was masked as an IMS bearing failure. The reason for this is the symptoms are exactly the same, damage is the same, the only difference is the chain of events. The IMS issue is so wide spread that lots of Dealerships are blaming any failure of significance on the IMS and some engines aren't being interrogated to verify this..

I recently had an 03 Boxster S that was shipped to us from 2,300 miles away for an engine install. It had been diagnosed improperly as an IMS bearing failure, but the IMS bearing was fine and the chain tensioner paddle was in 3 pieces.

The other MOF thats often misdiagnosed is the bank 4-6 drive sprocket on the IMS slipping and wiping out the entire 4-6 bank of valves due to altered valve timing. I permanently install the IMS drive sprockets with a proprietary process with every engine I build due to how many of these issues I have seen. Some have not wiped out the engines, but this slippage is the reason why most every engine we tear down has retarded cam timing on the 4-6 bank compared to 1-3.

In terms of rebuilding these engines, while not as simple as a small block Chevy, they are nothing more complex than any other German car engine. Yes, you need some special tools and the service manual with some added notes, but its a job that any competent engine builder can perform.

The service manual can get you in trouble fast, especially with cam timing. I built my first one without a manual and without a single Porsche tool. This engine is all about procedure and sequence.

Remember, any modern engine will experience very little wear if taken care of properly. Modern metallurgy, production techniques and tolerances, and modern lubricants have gone a long way toward making engines last well beyond 100K. The M96 is no exception.

Then why do so few M96s make it to that point?? I agree that there are exceptions, but I rarely get calls from anyone with more than 85K

There is no reason why these engines should not last 200K. The highest mileage engine I have torn down had 120K on the clock

Actually there are at least 19 reasons why some will not.. Thats how many modes of failure have been documented.

and the cylinder bores showed zero wear,

At what axis did you measure the bores? How many positions within the bore did you take your measurements? I'd be willing to bet that by that mileage the #2 and #5 cylinders had experienced taper beyond limits as well as ovality, especially at the mid-bore position.

main bearings had virtually undetectable wear, with the rod bearings showing mild wear

I concur. I have actually had used bearings PC2 coated and then reused them in test engines with excellent results. I did this when I first started working with these engines, before bearings could be bought easily. As long as the engine has not seen starvation issues it certainly has a god chance of having perfect bearings internally, probably to 200K.

The largest area of wear in most new car engines are the heads. The 120K heads were in need of new exhaust valves and a valve job.

Any head with 120K needs a valve job.. Exhaust valves always get replaced..

To everybody, don't sit home and freak out about your cars, go out and enjoy them the way they were designed!

Thats what we've been telling people for several years now.

I have made it a primary objective to understand these engines at a level that others have not. We had foresight with these engines and started working with them internally when people told us that we were dumb and were wasting our time because of how cheap a replacement engine was... Needless to say the foresight has been effective.

The things I have stated on my site and on this forum are based on the experience of myself and my team as well as the experience of shops that work with us as our affiliates across the country that see the same things we do.

Before most dealerships had the authorization to tear into the M96 to make repairs we'd already broken and reconstructed most every major component within the engine and we did it all without any assistance from the factory or PCNA.

Respect my experience, knowledge and statements and I'll do the same for you. If you have a problem or disagree with a statement I've made its much better to just come out and say it and direct the heat toward me- trust me, I can take it.

I'd like to hear more of your experiences and I am glad to see you here on the forums, we don't see many techs here.

With that I'll say that its much better to agree to disagree than get into a huge pissing contest between opinions. Pissing contests don't benefit anyone on this forum andI'll warn you now that I am very difficult to argue with.. I gather way too much info, take way too many pictures and have way too many notes to sit on the sidelines without substantiating my information. I go to the ends of the earth to gather this data and retain it just for "challenges" that are sure to come up from time to time.

I have over 1 Tb of data in my corner :-)

[mikefocke]

"Then why do so few M96s make it to that point?? I agree that there are exceptions, but I rarely get calls from anyone with more than 85K"

Maybe the reason you don't hear from high mileage owners with problems is because your prices are so high that they are just swapping in engines from wrecks as the only economically reasonable alternative to junking the car without investigating you beyond a quick internet price search. When the car is worth $10k running perfectly as many 986s are, it is hard to pay up to double that for an engine. It isn't like these will be collectibles and the emotional attachment of the owner may not be as high as we saw with 914s and 911s. Plus lots of 986 owners have a very different economic profile from the 914/911 owners. (Not disputing the worth of your work or the value received for the money you charge...just that it is high relative to the value of the car's value and so the sample you get is very selective. If my engine blows, I'll ship you my car but it wouldn't make economic sense as I could replace the car for 50-75% of the replacement engine cost. I'll do it for emotional reasons and because I can and not everyone is in that position.)

And I don't understand your wording that "so few M96s make it to that point". You don't hear from 85k+ Boxster owners who aren't having trouble so how can you compare failures to success numbers and say "so few"?

[Daniel R]

Originally Posted by mikefocke

"Then why do so few M96s make it to that point?? I agree that there are exceptions, but I rarely get calls from anyone with more than 85K"

Maybe the reason you don't hear from high mileage owners with problems is because your prices are so high that they are just swapping in engines from wrecks as the only economically reasonable alternative to junking the car without investigating you beyond a quick internet price search. When the car is worth $10k running perfectly as many 986s are, it is hard to pay up to double that for an engine. It isn't like these will be collectibles and the emotional attachment of the owner may not be as high as we saw with 914s and 911s. Plus lots of 986 owners have a very different economic profile from the 914/911 owners. (Not disputing the worth of your work or the value received for the money you charge...just that it is high relative to the value of the car's value and so the sample you get is very selective. If my engine blows, I'll ship you my car but it wouldn't make economic sense as I could replace the car for 50-75% of the replacement engine cost. I'll do it for emotional reasons and because I can and not everyone is in that position.)

And I don't understand your wording that "so few M96s make it to that point". You don't hear from 85k+ Boxster owners who aren't having trouble so how can you compare failures to success numbers and say "so few"?

You said it Mike.

It is all about sample size, but more importantly, a non-biased sample.

My 2000 S is approaching 80k miles and I have (thankfully) not encountered any of these issues yet. This does not make me an authority on these cars because 1 out of the many millions in the world has not gone bad by 80k.

It is my belief that the best thing anyone can do is to heed the warnings of those in the know, but at the same time use just a modicum of common sense to understand how and why the experts hold such opinions to be true. Nothing can beat backing up one's statements with hard facts and figures, after all, a measurement is not an opinion.