[player0]

Hi,

My first gen 987.1 3.4L spun a rod bearing with less than 50K miles. Using good summer tires but not R compounds. Religious oil changes, running good Motul oil. Had a deep sump pan and pickup installed. Did oil analysis regularly with no signs of any trouble. Car ran great until the sudden rod knock and failure which happened while doing a casual 40MPH. A bit of a turn but nothing high-G at that point. Only about 10K miles on that engine were mine. The crank, cylinder walls, just about everything on the bottom end were pooched.

I'm getting a new 3.4L motor, but reviewing the forums, these things seem to be manufactured out of cheese for how often they have issues. Before this new motor goes in, I'd like to do whatever I can to ensure this never happens again.

I know there are a lot of posts on this forum about oiling mods. Certainly the deep sump / baffled pan which I had. Accusump might have worked, but people here have had failures with those installed. Just too much lag time?

My mechanic believes this is a heat soak issue on the #6 bearing, not necessarily oil starvation. And that the oil layer breaks down. I trust what he's saying, but that sounds to me like a design flaw that won't be addressed by the usual oiling mods.

1.) Has anyone had these failures with a dry sump? This seems like overkill, and I'm just not sure the sump was the issue.

2.) I'm told building the motor fixes the issue. I know the rod bolts can stretch. I suppose clearances can be ensured, but why else does building these motors prevent the spun bearings? On it's own, it doesn't seem to address the main issue that the bearing loses oil pressure

3.) Is there some engine mod I'm missing? Crank oil porting or extra squirters or something that a builder of these engines needs to do to during a rebuild to fix the oiling issue? I've not found descriptions for what needs to be addressed internally during a rebuild.

Thanks for any tips, especially if you've had this engine rebuilt. I trust my mechanic to rebuild the engine right if he cracks the new one open. But I want to better understand the options as I frankly no longer trust these engines to stay in one piece.

 

[Croc'ed]

Hi,

My first gen 987.1 3.4L spun a rod bearing with less than 50K miles. Using good summer tires but not R compounds. Religious oil changes, running good Motul oil. Had a deep sump pan and pickup installed. Did oil analysis regularly with no signs of any trouble. Car ran great until the sudden rod knock and failure which happened while doing a casual 40MPH. A bit of a turn but nothing high-G at that point. Only about 10K miles on that engine were mine. The crank, cylinder walls, just about everything on the bottom end were pooched.

I'm getting a new 3.4L motor, but reviewing the forums, these things seem to be manufactured out of cheese for how often they have issues. Before this new motor goes in, I'd like to do whatever I can to ensure this never happens again.

I know there are a lot of posts on this forum about oiling mods. Certainly the deep sump / baffled pan which I had. Accusump might have worked, but people here have had failures with those installed. Just too much lag time?

My mechanic believes this is a heat soak issue on the #6 bearing, not necessarily oil starvation. And that the oil layer breaks down. I trust what he's saying, but that sounds to me like a design flaw that won't be addressed by the usual oiling mods.

1.) Has anyone had these failures with a dry sump? This seems like overkill, and I'm just not sure the sump was the issue.

2.) I'm told building the motor fixes the issue. I know the rod bolts can stretch. I suppose clearances can be ensured, but why else does building these motors prevent the spun bearings? On it's own, it doesn't seem to address the main issue that the bearing loses oil pressure

3.) Is there some engine mod I'm missing? Crank oil porting or extra squirters or something that a builder of these engines needs to do to during a rebuild to fix the oiling issue? I've not found descriptions for what needs to be addressed internally during a rebuild.

Thanks for any tips, especially if you've had this engine rebuilt. I trust my mechanic to rebuild the engine right if he cracks the new one open. But I want to better understand the options as I frankly no longer trust these engines to stay in one piece.

There's been some discussion about rod bolts stretching being the potential root cause of oil starvation/rod bearing failure in many of the blown M97 engines. Reportedly Porsche increased the rod bolt diameter on 9A1 engines, along with making significant oiling system upgrades. Since the 9A1 engines are seemingly much more durable, one can deduce that following Porsche's lead on the 9A1 upgrades would be a good path forward when rebuilding your M97.

Sent from my XT1650 using Tapatalk

 

[player0]

Thanks for the response. So rod bolt stretch causes the bearing failure, not vice versa. That'd be a compelling reason to upgrade the rods and rod bolts.

Then I'm left wondering if building a 3.4 motor is worth the effort versus dropping in the usual 3.8, or some other motor not made out of cheese. The S could use a bit more horsepower for sure. Will need to work with the mechanic to figure out what the best bang for the buck is.

 

[erikl]

All of the motors M96/M97 are similar, going 3.8 wont help, they have their own issues and have the same issues. LN and Flat Six claim to rebuild motors that addresses all of the issues. But they are $$$.

I have read that oiling issues on track are often related to the oil getting too hot and losing shear strength (something like that). Maybe your mechanic was referring to that in your statement above. I thought that was a track day problem and not an issue in street driving?

Maybe the car was tracked prior to your ownership?

I have not read about the rod bolt issue before, is that related to over revs or just normal use?

 

[Croc'ed]

All of the motors M96/M97 are similar, going 3.8 wont help, they have their own issues and have the same issues. LN and Flat Six claim to rebuild motors that addresses all of the issues. But they are $$$.

I have read that oiling issues on track are often related to the oil getting too hot and losing shear strength (something like that). Maybe your mechanic was referring to that in your statement above. I thought that was a track day problem and not an issue in street driving?

Maybe the car was tracked prior to your ownership?

I have not read about the rod bolt issue before, is that related to over revs or just normal use?

Rod bolt stretch would certainly be exacerbated by over-revs, so if indeed it is a root cause of some of the failures then keeping the revs below redline would be a good practice.
Without getting into what caused the failure, my intent was for the OP to consider Porsche's approach to designing the 9A1 engine when considering upgrade options for rebuilding his M97 engine. That seems like a logical path forward to me, considering the improved durability of the 9A1 vice the M97.

Sent from my XT1650 using Tapatalk

 

[husker boxster]

Rod bolt stretch would certainly be exacerbated by over-revs, so if indeed it is a root cause of some of the failures then keeping the revs below redline would be a good practice.

My thoughts too. OP, how much time did you spend in the 6-7K rpm range? How much track time?

 

[player0]

When I first purchased the car last year, I know the mechanic looked in to the over revs. I don't recall the exact figures from the Porsche computer, but there were something like 2-3 minor over revs and no major ones. The mechanic told me it was 'good' and nothing 'out of the ordinary'. I don't believe I've ever over revved it via downshift, it's something I make an effort to avoid for other reasons. I don't think it was unusual for me to shift in the upper RPM range. If I remember correctly, the powerband starts to taper around 6500 so I don't shift too close to redline. I've bounced off the rev-limiter on rare occasion but I don't think anything unusual.

I wasn't babying the engine but I don't think I was being abusive either. Or, I'm doing it wrong, and you're not supposed to push these things anywhere near redline?

The 3.8 being recommended is the 997 C2S motor. Don't know too much about it myself, I'm sure it has other issues to address, but wasn't sure it was a MY97 variant? I need to do some digging in to these things. I guess the 3.4 can also be bored to 3.8 or sleeved. I'll look in to those LN/Flat Six motors. Thanks!

 

[OmniGLH]

Send it to BGB for a 3.8.

They won't use the M97 out of the .1 CS - they'll use the DFI motor out of the .2. Much less "cheese" was used in those.

Probably spend about the same money too. Last I checked they were $18k + labor.

 

[player0]

Oh, BGB looks interesting too. Thanks for the tip. Great to get some real numbers to contrast and compare. I assumed the 3.8 build was going to be 20-30K and I was not wrong.

Dumping 30K in to a car I bought for 30K which still needs a decent suspension, exhaust, intake, LSD, and other fixings makes me wonder though. The built 3.8 caymans are wicked fast. But I'm thinking of spending 911 money now.

Think the next step is to find a 3.8 buddy and see if I can get a ride.

 

[Apex1]

OP, I assume that your mechanic split the case and examined #6 rod bearing closely to make the statement "this is a heat soak issue". Many of us would like to know more about what made him say that? Could he say that it had something to do with your motor oil and the temps you were subjecting your motor to. Or, was it a long term build up of coked surface that finally caused the bearing to fail like many old turbo bearings did when the hot engine was turned off and the oil coked in the turbo bearings. Many racers had similar issues before the 06 Cayman came out, so they used a deep sump with a windage tray to contain the oil to prevent oil starvation, but also thought that some oils are more susceptible to heat issues, so Joe Gibbs oil is recommended and a third radiator was installed. I have read that this issue usually occurs in the later half of the DE runs, so it has more to do with the breakdown of oil not protecting the bearing surface than oil starvation or both.
If you could add more light on what you have found out from your mechanic, I think a lot of us would like to know as we may be in the same risk category as you were and not know it. I have been using Castrol 5W-50 with ZDDP and change it every 4k miles, but would change to Joe Gibbs product if he thinks that protection would help. No DE's just autocross for me. Thanks.

 

[Apex1]

01-19-2016, 04:31 AM​

Voyager 6 Commented 1-16

"Even expensive race oil is cheap compared to having to pay for a new engine.

Some people use race oil and change before and after each event. I use Gibbs' Driven XP9 when on the track and their DT40 for the street. The 9A1 engine is designed to avoid oil starvation much more than the prior M9* engines, which often suffered oil starvation and bearing failure in high speed sweeping turns. with street oils.

The race oils have additive packages that take heat better and provide far more anti-friction additives, but they get used up quickly. XP9 is rated to only provide only 750 to 800 miles of protection. Regular motor oils have an additive package that doesn't provide the same protection, with more concern to have the additives last the life of the oil. So there is less protection in the race environment with street oils regardless of the color when it comes out.

In my car, because of the extensive thermal insulation on the intake and exhaust, the engine oil doesn't get over 210F on track, so the additives in XP9 probably don't get used up at the expected rate."


OP, Did your mechanic recommend any solution that would have prevented the spun bearing? Thanks, K

 

[Sapientoni]

Are you sure it's the rod bearing? I sped thru all the posts and didn't see if you conclusively saw it. The cruising and then suddenly rod knocking makes me suspect IMSB. A spun bearing doesn't get that bad that fast. An IMSB does. A friend with a 914-6 drove it to Road Atlanta, about 180 miles and back with the engine oil temp pegged. It would cool down at idle on the side of the road while we were checking everything. Turned out to be exhaust restriction causing hi speed overheating, just cruising at high speed. I can help you if it's the IMSB.

Good Luck. I go back and look over the other posts again.

 

[player0]

It was 100% a spun bearing. My understanding is that IMS failures are less common on the 3.4L 987 motors but I have also had people recommend replacing it. Including my mechanic.

Anyway, good news is I got the car back yesterday with a re-manufactured stock engine. The insurance company refused to simply cut us a check and simply sent a full replacement engine and *some* of the cost to install it. Breaking it in now. I get 1-2 years of warranty on the new engine and apparently I still have an insurance policy so if anything else fails I'll be covered.

As far as deeper failure analysis, I don't have more information. I don't want to speak for my mechanic but I think in his eyes this was an obvious case of 'engine saw too much action, was not built'. I had a good oil in there and the oiling mods, but who knows what the previous owner had done.

His recommended solution is building the motor. I mean, he builds motors for people who track heavily and do not want to mess around with 'maybe'. There might be cheaper ways to solve the issue but I don't blame a performance shop for recommending the safest bet. It's their bread and butter after all.

On oiling, I think I covered it above, but I don't think I ever had any oil in there that saw more than 1000 miles. It wasn't full racing oil, I think Motul 8100 Xmax, not the 300V, though changed very frequently and continuously lab tested.

My take away on this: I don't think race oil or minor oiling mods are going to save this engine. I think these engines will handle 30-40 track days with no sign of issue and suddenly give up the ghost at a seemingly random time. Based on the information available online, I don't think anyone should be surprised about this type of failure if doing any sort of high performance driving in a gen 1 cayman. Some people get lucky and deep sumps probably help delay the issue. I've discussed this personally with at least 4 different pro porsche shops in the area and no one is at all surprised about this engine and this result.

At least I get a daily driver back with at least a year of warranty on it. I'm going to be very gentle, meanwhile saving up for a mean 4.0 build. Shop is doing a 4.0 for another customer and I'll let them guinea pig it

Finally, want to give a shout out to this shop. I have never had such a good experience before. The car drives great, was completed on time, communication was great. I've spent 2017 fighting with other shops and other cars and other blown motors and it's a nightmare. I'm not sure I'm allowed to promote names here in public, but if anyone is looking for a fantastic performance Porsche shop in new england, drop me a PM.

 

[Sapientoni]

pictures please, the masses want to see pictures. I try to always show when telling. My friend with a 914-6 was running Mobil 1 on our second trip (first long trip after rebuilding for the #6 spun bearing in 2.2) drove it from Charlotte to Atlanta and back a second time with temp gauge pegged. With Mobil 1 it was only pecking faintly when we got back. But still it was "lead gone" bearing damaged. Turned out air cooled engines hate back pressure, even when just cruising on the highway. He had stuffed steel wool into the p.o. modified muffler trying to quiet it down to bearable. No problem, BUTT, this engine was pumping oil and the oil soot was clogging up the muffler, restricting the exhaust. The restriction had insidiously built up and he hadn't noticed it because it was so gradual.

 

[desmotesta]

By insurance company do you mean "extended warranty" company?

 

[toy4two]

By insurance company do you mean "extended warranty" company?

must be I don't know any insurance company that would cover a blown engine, but I'd happily switch to them if there is such a thing!

 

[desmotesta]

OP: You mentioned you tok great care of the care, religious oil changes etc.. BUT only 10K of 50K miles was under your watch. You can't be sure of how it was cared for, driven, over-revved or abused/neglected before your ownership. Lots of people out there, who shine and polish their cars every weekend, freak out when they have a small stone chip or wheel scrub, yet are obtuse when it comes to mechanical maintenance and care, go 10-12K miles on old oil, start the car up first thing in the morning and go full throttle, miss shifts, over rev while red light racing etc etc etc

Its a crappy situation to be in. Looks like your car is covered under warranty and thats a good thing.

 

[player0]

Yeah, an aftermarket warranty the used car dealership forced down my throat saved my butt.

So absolutely right, I can't be sure the level of abuse the car received before me. But, with small world luck, my mechanic knew the car through the original owner. Somewhat coincidental. But there was quite a bit I did to review the engine before purchase. It was scoped for cylinder wall damage. Two years of oil analysis showed no bearing material. The Porsche computer actually counts minor and major over-revs. There were only two minor events logged, pretty typical AFAIK.

Much more important than the PO, I know what my contribution was to the motor.