Connecting rod bolt failure.... is this really a thing?
03-23-2019, 12:27 PM
#1
Rennlist Member
Thread Starter
Connecting rod bolt failure.... is this really a thing?
Looking at a nice 2007 Cayman S.
Then I happened across some talk about connecting rod bolts in these cars stretching and letting go, or resulting in spun rod bearings....
... is this for real?
I can deal with the IMS / RMS thing, but not looking to open the engine up to deal with the rotating assembly.
Then I happened across some talk about connecting rod bolts in these cars stretching and letting go, or resulting in spun rod bearings....
... is this for real?
I can deal with the IMS / RMS thing, but not looking to open the engine up to deal with the rotating assembly.
03-23-2019, 04:19 PM
#2
Rennlist Member
If the engine hasn't been over-revved, doesn't have a tune that has raised the rev limiter, and it's been a street car its whole life, I'm not too concerned with rod bolt failures.
03-24-2019, 01:03 PM
#3
Rennlist Member
Thread Starter
Having spent the better part of last night researching this specific topic, it looks like engine failures due to connecting rod bolt stretch are a well known issue with any Cayman / Boxster / 911 built prior to MY09 (the M97 engines). It doesn’t take long to look up Porsche M97 on YouTube and watch the analysis videos of engines that let go.
Yes, it seems to be a result of high RPM use... but these ARE Porsche’s we’re talking about. What good is a sports car that can’t be revved very much...?
It also seems to be regardless of any aftermarket “tuning” or whatever.
So I can buy a Cayman S, but I can’t take it to a simple track day or an AutoX and have any confidence that the engine won’t let go? That’s pretty sad, for Porsche. I might expect that of other less sport inclined brands, but not from Porsche. And I’m not talking about just driving around bouncing off the rev limiter all the time, I’m talking about normal track day / AutoX use.
Looks like the solid recommendation at this point is to look for an ‘09+.
03-24-2019, 07:44 PM
#4
Rennlist Member
Hmmm.
Having spent the better part of last night researching this specific topic, it looks like engine failures due to connecting rod bolt stretch are a well known issue with any Cayman / Boxster / 911 built prior to MY09 (the M97 engines). It doesn’t take long to look up Porsche M97 on YouTube and watch the analysis videos of engines that let go.
Yes, it seems to be a result of high RPM use... but these ARE Porsche’s we’re talking about. What good is a sports car that can’t be revved very much...?
It also seems to be regardless of any aftermarket “tuning” or whatever.
So I can buy a Cayman S, but I can’t take it to a simple track day or an AutoX and have any confidence that the engine won’t let go? That’s pretty sad, for Porsche. I might expect that of other less sport inclined brands, but not from Porsche. And I’m not talking about just driving around bouncing off the rev limiter all the time, I’m talking about normal track day / AutoX use.
Looks like the solid recommendation at this point is to look for an ‘09+.
03-24-2019, 07:59 PM
#5
Rennlist Member
I’ve been in these 996 forums for 2 years and don’t think I’ve ever heard of a rod bolt failure for these M96 engines. I also don’t remember this to be an issue when I had my 987.
That said, any overreved engines, no matter the make or model, can suffer from rod bolt failure. I’ve heard this on BMWs more than Porsche.
I have, however, heard of rod bearing wear due to direct injection and low RPM/high boost engines.
EDIT: I heard of GT3 engine failures, though: https://www.callasrennsport.com/File...e-Failures.pdf
That said, any overreved engines, no matter the make or model, can suffer from rod bolt failure. I’ve heard this on BMWs more than Porsche.
I have, however, heard of rod bearing wear due to direct injection and low RPM/high boost engines.
EDIT: I heard of GT3 engine failures, though: https://www.callasrennsport.com/File...e-Failures.pdf
Last edited by Mike Murphy; 03-25-2019 at 09:39 AM.
03-25-2019, 10:56 AM
#6
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That's why my buddy and I went halves on a 944S for the track. We blew the motor last season after four seasons. We got $400 for the shell. The Hawk blue pads and SS brake lines cost more. But the laughs were worth it. Cant say I would laugh if the motor on my Cayman S went on the track knowing a rebuild would cost 20-25 without a core. The Cayman is a street car. The line that a Porsche is a race car for the street is no longer applicable.
Besides an accusump what should one do to protect the motor if the car will see DEs?
Besides an accusump what should one do to protect the motor if the car will see DEs?
03-25-2019, 04:10 PM
#7
Rennlist Member
That's why my buddy and I went halves on a 944S for the track. We blew the motor last season after four seasons. We got $400 for the shell. The Hawk blue pads and SS brake lines cost more. But the laughs were worth it. Cant say I would laugh if the motor on my Cayman S went on the track knowing a rebuild would cost 20-25 without a core. The Cayman is a street car. The line that a Porsche is a race car for the street is no longer applicable.
Besides an accusump what should one do to protect the motor if the car will see DEs?
Besides an accusump what should one do to protect the motor if the car will see DEs?
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03-31-2019, 10:27 AM
#8
Race Director
I’ve been in these 996 forums for 2 years and don’t think I’ve ever heard of a rod bolt failure for these M96 engines. I also don’t remember this to be an issue when I had my 987.
That said, any overreved engines, no matter the make or model, can suffer from rod bolt failure. I’ve heard this on BMWs more than Porsche.
I have, however, heard of rod bearing wear due to direct injection and low RPM/high boost engines.
EDIT: I heard of GT3 engine failures, though: https://www.callasrennsport.com/File...e-Failures.pdf
That said, any overreved engines, no matter the make or model, can suffer from rod bolt failure. I’ve heard this on BMWs more than Porsche.
I have, however, heard of rod bearing wear due to direct injection and low RPM/high boost engines.
EDIT: I heard of GT3 engine failures, though: https://www.callasrennsport.com/File...e-Failures.pdf
Both my 2002 Boxster and my 2003 996 Turbo saw high revs once the engine was up to full operating temperature. I never even gave a 2nd thought about rod bolt failure. (The Boxster engine had 317K miles on it, the Turbo 161K miles.)
03-31-2019, 11:59 AM
#9
Rennlist Member
Been following the Boxster/996 engines way more than 2 years. Rod bolt failure is very rare. Charles N. is spot on regarding his comments. Stock engine with factory "tune" and with no one having been at the engine, rod bolt failure is way way down the list of things that will take out one of these engines.
Both my 2002 Boxster and my 2003 996 Turbo saw high revs once the engine was up to full operating temperature. I never even gave a 2nd thought about rod bolt failure. (The Boxster engine had 317K miles on it, the Turbo 161K miles.)
Both my 2002 Boxster and my 2003 996 Turbo saw high revs once the engine was up to full operating temperature. I never even gave a 2nd thought about rod bolt failure. (The Boxster engine had 317K miles on it, the Turbo 161K miles.)
Peter