996 Engine Whine - Is this normal on recentlyrebuilt engine?
Discussion
Thank god I'm not alone, I have the same noise on mine that has been the same since my rebuild, I have listened with a stethoscope but I'm unable to pinpoint it.
I have two theories, the first that the IMS bearing now doesn't have any oil seals on it to soften the sound of the bearing, but I would think any bearing that's lubricated correctly shouldn't make this noise, my second thought is an air leak maybe sucking air in somewhere, either at the intake area or the air oil separator. Its a kind of supercharger noise and that's what makes me think air leak.
I did take mine up to Hartech for Baz to have a listen but he was not at work that day and another guy there said he thought the sound was normal, the thing is I know the the noise wasn't there before my rebuild. Just to clarify I rebuilt my own engine not Hartech.
If you do ever get to the bottom of this let me know..
I have two theories, the first that the IMS bearing now doesn't have any oil seals on it to soften the sound of the bearing, but I would think any bearing that's lubricated correctly shouldn't make this noise, my second thought is an air leak maybe sucking air in somewhere, either at the intake area or the air oil separator. Its a kind of supercharger noise and that's what makes me think air leak.
I did take mine up to Hartech for Baz to have a listen but he was not at work that day and another guy there said he thought the sound was normal, the thing is I know the the noise wasn't there before my rebuild. Just to clarify I rebuilt my own engine not Hartech.
If you do ever get to the bottom of this let me know..
While on this topic, my C4S does this, not all the time, but if it hasn't been used for a day or two. By the way, this isn't my one, just a clip I found on Youtube, but the sound is identical.
http://www.youtube.com/watch?v=WMs3ieE81oQ
Any suggestions?
http://www.youtube.com/watch?v=WMs3ieE81oQ
Any suggestions?
angrybob said:
Hi all,
Thanks for your feedback.
Just to clarify regarding Hartech, they are 250 miles away from me right now and the rebuild (quite extensive) was from the previous owner of the car about 15months ago. I have all the details/job#. I preferred the approach of asking what is normal before I begin to bother what is a clearly very busy and reputable shop, and I would understand their reluctance to diagnose via a youtube clip and would much rather see a car in person.
Apologies for the name mention, this was from a positive viewpoint due to their considerable reputation I wouldn't expect there to be any problem. No malice intended as the engine sounds streets ahead of non rebuilt engines.
Regarding running with no belt, that was a stone cold engine running for 10s at most, and I figured it was worth the diagnostic as I would have been asked to try this anyway (or the local Indy would have done right away).
So looks like most people say this is normal for a 996 to sound like a whiney sewing machine (to me it sounds like a knackered bearing!). I think I will get some more reference points this weekend with other 996/986 and report back.
Thanks for input.
Well, I for one say it sounds ok to me but I'm not at the car. My Turbo was "quiet" for thousands of miles then I noticed it wasn't quiet, at least as quiet as it had been. Best I can describe the sound: A "dry bearing".Thanks for your feedback.
Just to clarify regarding Hartech, they are 250 miles away from me right now and the rebuild (quite extensive) was from the previous owner of the car about 15months ago. I have all the details/job#. I preferred the approach of asking what is normal before I begin to bother what is a clearly very busy and reputable shop, and I would understand their reluctance to diagnose via a youtube clip and would much rather see a car in person.
Apologies for the name mention, this was from a positive viewpoint due to their considerable reputation I wouldn't expect there to be any problem. No malice intended as the engine sounds streets ahead of non rebuilt engines.
Regarding running with no belt, that was a stone cold engine running for 10s at most, and I figured it was worth the diagnostic as I would have been asked to try this anyway (or the local Indy would have done right away).
So looks like most people say this is normal for a 996 to sound like a whiney sewing machine (to me it sounds like a knackered bearing!). I think I will get some more reference points this weekend with other 996/986 and report back.
Thanks for input.
I was on the road and at a hotel parking lot spotted an older Carrera and when I spotted a guy walking up to the car I pulled in and jumped out and asked if he'd give a listen. He did and agreed with me it was "dry bearing" sound.
Then I found an auto repair shop open and I spoke to the owner and he put the car in the air. We got under the car and checked for leaks, etc. Nothing. But there was a noise that sounded like it was coming from up high at the back of the car around the power steering pump. Oh, he agreed it was a "dry bearing" sound.
Faced with 4K miles ahead of me or 200 miles back home I turned around and drove home and at the dealer a day or two later a bad serpentine belt idler bearing was found to be the cause of the noise. The one up high right next to the power steering pump.
But I had months and months of becoming acquainted with my car and its sounds under a variety of conditions.
If in your opinion the noise is new and obviously troubling you get it listened to by an expert, experienced tech.
IOWs, get a second opinion from someone that can hear the noise from the car directly.
There are one or two interesting / scary clips called up by that link - including this one -
http://www.youtube.com/watch?v=ERtwVAy_4H0
Porsche 996 Catastrophic IMS Bearing Failure
The suggestion is that there is an upgrade which it is wise to implement to avoid falling victim to this 'known Porsche problem'. Do you agree?
http://www.youtube.com/watch?v=ERtwVAy_4H0
Porsche 996 Catastrophic IMS Bearing Failure
The suggestion is that there is an upgrade which it is wise to implement to avoid falling victim to this 'known Porsche problem'. Do you agree?
cardigankid said:
There are one or two interesting / scary clips called up by that link - including this one -
http://www.youtube.com/watch?v=ERtwVAy_4H0
Porsche 996 Catastrophic IMS Bearing Failure
The suggestion is that there is an upgrade which it is wise to implement to avoid falling victim to this 'known Porsche problem'. Do you agree?
If you're asking me, my thoughts are you need to ensure the noise that prompted your initial query is not something serious, from "just" a bad idler roller bearing to something worse.http://www.youtube.com/watch?v=ERtwVAy_4H0
Porsche 996 Catastrophic IMS Bearing Failure
The suggestion is that there is an upgrade which it is wise to implement to avoid falling victim to this 'known Porsche problem'. Do you agree?
Get that noise issue settled, first, would be my advice.
Then if you want to consider having an IMSB upgrade (intermediate shaft bearing) installed that' a whole 'nother question.
These engines do have several odd noises - mainly because there are 3 or 5 chains thrashing around, sprockets, several hydraulic tensioners, complex tappets (as you get to variocam plus), cam timing solenoids with hydraulic tensioners and valving, and especially 2 banks of cylinders largely exposed to the outside World and close to reflective metal shields etc. Chain sprockets wear and chains stretch (which then run chains more loosely as they no longer fit the sprockets perfectly (even new chains on old sprockets suffer from this).
Then there are coolant pumps, alternators that rain can dip on to, power steering pumps on top of the engine and several grease filled rollers and dry running gears and a drive belt. Even the air oil separator and various systems to extract the harmful bi-products of combustion (not to mention those with air pumps) and automatic gearboxes and torque converters, tired dual mass flywheels (this list is not exhaustive) - all contribute to unbalanced or un-damped engine speed fluctuations on tick over and hence noise potential that is more often hidden under a front bonnet and insulated from the driver by carpet etc (where the only reflective surface is in front of the driver and behind the dashboard) whereas the slopping rear window of a 911 (or engine cover of a Boxster) reflect a lot of noise from the engine area as well into the car (and Sports cars do not want to carry heavy sound insulation weights).
It all adds up to potential for odd noises that worry people - in most cases unnecessarily.
The firing order also doesn't help being 1 6 2 4 3 5 making the 1 to 6 fire at opposite ends of the relatively flexible crankshaft and produce a torsional snatch to the 2 IMS shaft chains (with drive sprockets on each end) and to the chain and hydraulic tensioner system on tick over. This can result in a ticking noise at half engine speed that is often indistinguishable from a badly worn tappet, weak hydraulic chain tensioner or even piston slap.
This is mainly because at tick over there is hardly any fuel being fed to the cylinders and very little air and the firing sequences in any engine actually make the crankshaft speed up and slow down between each "bang" that accelerates and decelerates the engine. As the speed increases several things change. The oil pressure rises quickly (which tightens tensioners and tappets), the oil supplied to the cylinders through the oil spray jets increases and the speed and inertia of the crankshaft reduce the time available for the speeding up and slowing down between power pulses to reach the other end of the slack tension in the drive train before the next power pulse - so it usually disappears immediately the revs rise.
In some cases even a rebuilt engine can pick up a tick over tick as a result of the mixture of new, reconditioned and older components slightly unbalance the firing pulses on tick over.
Wear in cylinders and pistons (or going oval), differences in valve sealing (needing reconditioning), slight changes in fuel injector performance - all change the fine balance between all the cylinders - on tick over - which is much more noticeable than when the throttle is more open and the proportional differences fade away - so the most unbalanced proportional individual piston loads occur on tick over as well.
All this is a recipe for worry because all these engines in particular have the potential for lots of odd noises - most of which are entirely innocent and have no adverse influence on reliability whatsoever.
Indeed it probably needs more than one clue as to the problem to correctly diagnose otherwise similar noises (like a sootier rear exhaust on one side combined with increased oil consumption and a camera view down the bores - might implicate a scored bore when the same noise without any of the other clues may just be due to general imbalance of the tiring engine components on tick over.
Apart from metallic screeches (that may be the IMS bearing and that do not disappear the minute the throttle is opened) most noises are just a feature of these engines and should mainly be ignored.
Even specialists (whatever they claim) would find it impossible to diagnose exactly what the cause of some noises is and if they need attention or not (usually not).
So it is probably best to ignore such noises and make sure however that it is covered by some kind of reliable warranty - if it does actually need the engine fixing one day (which it probably will not).
More relevant issues that should require attention would be running temperature changes, smoke (particularly from one exhaust only), sudden changes that lower tick over oil pressure significantly, debris in the oil filter.
Now please guys don't start picking on this general advice by arguing individual experiences that vary. We see more of these engines with problems than anyone else (and quite a lot that are noisy but OK) and these conclusions are general and apply on average and most often and therefore are good well intentioned general advice. There are always rare exceptions but discussing them offers nothing constructive to readers overall as the particular differences in those cases are unlikely to ever affect anyone else.
Baz
Then there are coolant pumps, alternators that rain can dip on to, power steering pumps on top of the engine and several grease filled rollers and dry running gears and a drive belt. Even the air oil separator and various systems to extract the harmful bi-products of combustion (not to mention those with air pumps) and automatic gearboxes and torque converters, tired dual mass flywheels (this list is not exhaustive) - all contribute to unbalanced or un-damped engine speed fluctuations on tick over and hence noise potential that is more often hidden under a front bonnet and insulated from the driver by carpet etc (where the only reflective surface is in front of the driver and behind the dashboard) whereas the slopping rear window of a 911 (or engine cover of a Boxster) reflect a lot of noise from the engine area as well into the car (and Sports cars do not want to carry heavy sound insulation weights).
It all adds up to potential for odd noises that worry people - in most cases unnecessarily.
The firing order also doesn't help being 1 6 2 4 3 5 making the 1 to 6 fire at opposite ends of the relatively flexible crankshaft and produce a torsional snatch to the 2 IMS shaft chains (with drive sprockets on each end) and to the chain and hydraulic tensioner system on tick over. This can result in a ticking noise at half engine speed that is often indistinguishable from a badly worn tappet, weak hydraulic chain tensioner or even piston slap.
This is mainly because at tick over there is hardly any fuel being fed to the cylinders and very little air and the firing sequences in any engine actually make the crankshaft speed up and slow down between each "bang" that accelerates and decelerates the engine. As the speed increases several things change. The oil pressure rises quickly (which tightens tensioners and tappets), the oil supplied to the cylinders through the oil spray jets increases and the speed and inertia of the crankshaft reduce the time available for the speeding up and slowing down between power pulses to reach the other end of the slack tension in the drive train before the next power pulse - so it usually disappears immediately the revs rise.
In some cases even a rebuilt engine can pick up a tick over tick as a result of the mixture of new, reconditioned and older components slightly unbalance the firing pulses on tick over.
Wear in cylinders and pistons (or going oval), differences in valve sealing (needing reconditioning), slight changes in fuel injector performance - all change the fine balance between all the cylinders - on tick over - which is much more noticeable than when the throttle is more open and the proportional differences fade away - so the most unbalanced proportional individual piston loads occur on tick over as well.
All this is a recipe for worry because all these engines in particular have the potential for lots of odd noises - most of which are entirely innocent and have no adverse influence on reliability whatsoever.
Indeed it probably needs more than one clue as to the problem to correctly diagnose otherwise similar noises (like a sootier rear exhaust on one side combined with increased oil consumption and a camera view down the bores - might implicate a scored bore when the same noise without any of the other clues may just be due to general imbalance of the tiring engine components on tick over.
Apart from metallic screeches (that may be the IMS bearing and that do not disappear the minute the throttle is opened) most noises are just a feature of these engines and should mainly be ignored.
Even specialists (whatever they claim) would find it impossible to diagnose exactly what the cause of some noises is and if they need attention or not (usually not).
So it is probably best to ignore such noises and make sure however that it is covered by some kind of reliable warranty - if it does actually need the engine fixing one day (which it probably will not).
More relevant issues that should require attention would be running temperature changes, smoke (particularly from one exhaust only), sudden changes that lower tick over oil pressure significantly, debris in the oil filter.
Now please guys don't start picking on this general advice by arguing individual experiences that vary. We see more of these engines with problems than anyone else (and quite a lot that are noisy but OK) and these conclusions are general and apply on average and most often and therefore are good well intentioned general advice. There are always rare exceptions but discussing them offers nothing constructive to readers overall as the particular differences in those cases are unlikely to ever affect anyone else.
Baz
I for one will be forever in Baz's debt. That was a comprehensive comfort blanket of a contribution. Hopefully my '02 996 will never go wrong but if it does I will be employing your services to sort it out. Now let's hope for a bit of sunshine so we can all stop worrying and go and actually enjoy our slightly eccentric, undoubtedly noisy supercars. Cheers!
Thanks and don't forget the tickover stability is also a function of the ignition timing, injector pulse width, oxygen sensor feedback and cam position sensors - since all these can alter the tickover speed as a result of feedback.
Even if the engine is mechanically perfectly balanced with all individual cylinder functions balanced - with such a complex - multi linked system and the crankspeed sensor recording each rev (and changes) the cam position sensor picking up every 2 revs and the oxygen sensor permanent while the idle speed controller is trying to adjust the airflow to stabilise the tickover speed - any slight imbalance can set up cyclic surges that result in lumpy tickovers and often resulting worrying noises.
Previous air cooled 911 models had the cam chains both driven from a position next to each other (eliminating some potential for torsional shaft and linear chain tension fluctuations - whereas this engine has a chain at each end of a hollow shaft driven by another (where earlier engines intermediate shafts were driven by a helical gear) so introduces more and more potential for flexing and instability.
As the crankshaft speed increases it becomes a control system in which the inertia of the parts cannot respond quickly enough to need too much control and dampens down surges - but as the speed reduces those power pulses have longer to wait fot he next one and that time can begin to set up surges.
Baz
Even if the engine is mechanically perfectly balanced with all individual cylinder functions balanced - with such a complex - multi linked system and the crankspeed sensor recording each rev (and changes) the cam position sensor picking up every 2 revs and the oxygen sensor permanent while the idle speed controller is trying to adjust the airflow to stabilise the tickover speed - any slight imbalance can set up cyclic surges that result in lumpy tickovers and often resulting worrying noises.
Previous air cooled 911 models had the cam chains both driven from a position next to each other (eliminating some potential for torsional shaft and linear chain tension fluctuations - whereas this engine has a chain at each end of a hollow shaft driven by another (where earlier engines intermediate shafts were driven by a helical gear) so introduces more and more potential for flexing and instability.
As the crankshaft speed increases it becomes a control system in which the inertia of the parts cannot respond quickly enough to need too much control and dampens down surges - but as the speed reduces those power pulses have longer to wait fot he next one and that time can begin to set up surges.
Baz
Baz
I don't like to intrude on your generosity in commenting - I had actually been getting a little concerned about lumpy tickover - my Jag by contrast ticks over smooth as silk.
However, have you any views on the screeching sound which follows immediately after I use the starter motor?
http://www.youtube.com/watch?v=WMs3ieE81oQ
(I am in Glasgow so it isn't an easy thing to drop the car in. I prefer if I can to get any issues dealt with at the same time as a service.)
I don't like to intrude on your generosity in commenting - I had actually been getting a little concerned about lumpy tickover - my Jag by contrast ticks over smooth as silk.
However, have you any views on the screeching sound which follows immediately after I use the starter motor?
http://www.youtube.com/watch?v=WMs3ieE81oQ
(I am in Glasgow so it isn't an easy thing to drop the car in. I prefer if I can to get any issues dealt with at the same time as a service.)
My last car before my current 996 C2 was a tuned Audi C5 RS6 with Milltek pipes. That sounded like an earthquake at low revs and a hurricane when the turbos spooled up.
I'm still not used to the sound of the 911 after a succession of V6s and V8s. I like the noise a lot but it's unlike any other car I've ever heard. I think it sounds like some kind of spaceship when you get to the upper reaches of the rev range.
I'm still not used to the sound of the 911 after a succession of V6s and V8s. I like the noise a lot but it's unlike any other car I've ever heard. I think it sounds like some kind of spaceship when you get to the upper reaches of the rev range.
My car went into OPC Guildford other week for what i thought was a water pump bearing or something like that. Was making a noise at low engine and road speed. Guys there had it in and it turned out it was a couple of exhaust brackets that had snapped which was probably causing it to resonate, sounding like a bearing. Had the work done once the brackets turned up from Germany and everything is fine. Only drama is now there is a new noise which i definitly know what that is and confirmed with OPC is the baffles have gone in one side. They do make funny noises and sometimes as above, not what you think it is. Take it to Hartech or even to your local OPC. I got a Panamera out of them for 2 days, they did a safety check on the car and diagnosed the problem.
We have even heard a metallic tap (you would swear it was metallic) caused by an exhaust leak into the AGR vents.
When you consider all the parts and systems I have highlighted above - you then compare that to a straight 4 or 6 with a single cam driven by one belt the reasons for so many potential noise sources compared to other engines becomes more clear.
Even many V8's have far less driven and flexing parts.
Furthermore having a cam drive on each end of the crankshaft and an overhanging flywheel increases crankshaft flex.
Noisy they are - great to drive - they are - noisy likely to be signs of problems - that are more often than not - not!
Going back 40 years my 2.2 911T (with 6 inlet trumpets drawing in air just below the rear parcel shelf) was so noisy the answer was a good tape - loud - perhaps with our more sophisticated sound systems the same solution could be worth considering!
Baz
When you consider all the parts and systems I have highlighted above - you then compare that to a straight 4 or 6 with a single cam driven by one belt the reasons for so many potential noise sources compared to other engines becomes more clear.
Even many V8's have far less driven and flexing parts.
Furthermore having a cam drive on each end of the crankshaft and an overhanging flywheel increases crankshaft flex.
Noisy they are - great to drive - they are - noisy likely to be signs of problems - that are more often than not - not!
Going back 40 years my 2.2 911T (with 6 inlet trumpets drawing in air just below the rear parcel shelf) was so noisy the answer was a good tape - loud - perhaps with our more sophisticated sound systems the same solution could be worth considering!
Baz
cardigankid said:
While on this topic, my C4S does this, not all the time, but if it hasn't been used for a day or two. By the way, this isn't my one, just a clip I found on Youtube, but the sound is identical.
http://www.youtube.com/watch?v=WMs3ieE81oQ
Any suggestions?
I am pretty sure you need a new starter...http://www.youtube.com/watch?v=WMs3ieE81oQ
Any suggestions?
Edited by Stefandk on Sunday 19th May 12:47
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