A $600 Oil Change
01-04-2009, 03:34 PM
#31
Race Car
The mounts are not designed to be compressed with 1000+ pounds. Just because there are a few exceptions where damage does not occur or has occured and is not noticed, does not mean it is the best way to lift the car.
01-04-2009, 05:48 PM
#32
Three Wheelin'
Here is where we disagree. It appears that your position is that lifting a 911 by the engine is the root and sole cause of motor mount failure. Unfortunately your position is not correct.
The root cause of motor mount failure is simple wear and tear failure. A mount in good repair can handle both positive and negative torsion compression from engine movement, but over time the flexible materials in the mount degrades, and will eventually become brittle and will crack releasing the isolation fluid that is contained in the mount. This is true for not only 996 mounts, but also for mounts from other german manufacturers, especially Audi and VW. Under normal use a mount will usually last about 6-10 years or 100K miles. Severe use can cause the mount to degrade and fail much earlier. (Trivia fact, 996 motor mounts have a 993 part number)
996/997 owners who may not be mechanically adept or have a good understanding of the mechanical or electrical subsystems in their cars could come to the conclusion that if a motor mount failure event happens during lifting the car, that the lifting event is the cause, but the reality is that the mount was doomed well before it failed.
I maintain that if a mount was bound to fail, that it is best that the mount failed when it could draw attention to its condition. Lifting the car using the engine as a mount is a very good way to determine the serviceability of the mounts.
Many 911 owners drive their cars for months if not years with failed mounts and are none the wiser. Their only indication that something may be amiss is an increased level of NVH or that the muffler tips seem to be lower that what they were.
As a part of normal oil change maintenance, I recommend that the condition of the mounts be examined. If there is any purple or dark liquid stains on the mount bottom or the rear engine cross brace, then the mount has failed and needs to be replaced. Replacing a mount is a very easy DIY process.
To replace a mount, simply support the engine with a jack, then remove the bottom bolt securing the mount to the engine, then from the engine bay, remove the 2 top securing bolts, lift the mount out, and drop the new one it and secure it. Note: It is necessary to remove either the air box or secondary air pump to gain access to the mounts. Retail on a replacement mount is about $150, but can be had for less. If you are capable of using a ratchet wrench, you can R&R the mount in under 30 minutes.
The root cause of motor mount failure is simple wear and tear failure. A mount in good repair can handle both positive and negative torsion compression from engine movement, but over time the flexible materials in the mount degrades, and will eventually become brittle and will crack releasing the isolation fluid that is contained in the mount. This is true for not only 996 mounts, but also for mounts from other german manufacturers, especially Audi and VW. Under normal use a mount will usually last about 6-10 years or 100K miles. Severe use can cause the mount to degrade and fail much earlier. (Trivia fact, 996 motor mounts have a 993 part number)
996/997 owners who may not be mechanically adept or have a good understanding of the mechanical or electrical subsystems in their cars could come to the conclusion that if a motor mount failure event happens during lifting the car, that the lifting event is the cause, but the reality is that the mount was doomed well before it failed.
I maintain that if a mount was bound to fail, that it is best that the mount failed when it could draw attention to its condition. Lifting the car using the engine as a mount is a very good way to determine the serviceability of the mounts.
Many 911 owners drive their cars for months if not years with failed mounts and are none the wiser. Their only indication that something may be amiss is an increased level of NVH or that the muffler tips seem to be lower that what they were.
As a part of normal oil change maintenance, I recommend that the condition of the mounts be examined. If there is any purple or dark liquid stains on the mount bottom or the rear engine cross brace, then the mount has failed and needs to be replaced. Replacing a mount is a very easy DIY process.
To replace a mount, simply support the engine with a jack, then remove the bottom bolt securing the mount to the engine, then from the engine bay, remove the 2 top securing bolts, lift the mount out, and drop the new one it and secure it. Note: It is necessary to remove either the air box or secondary air pump to gain access to the mounts. Retail on a replacement mount is about $150, but can be had for less. If you are capable of using a ratchet wrench, you can R&R the mount in under 30 minutes.
01-04-2009, 06:11 PM
#33
Race Car
Here is where we disagree. It appears that your position is that lifting a 911 by the engine is the root and sole cause of motor mount failure. Unfortunately your position is not correct.
The root cause of motor mount failure is simple wear and tear failure. A mount in good repair can handle both positive and negative torsion compression from engine movement, but over time the flexible materials in the mount degrades, and will eventually become brittle and will crack releasing the isolation fluid that is contained in the mount. This is true for not only 996 mounts, but also for mounts from other german manufacturers, especially Audi and VW. Under normal use a mount will usually last about 6-10 years or 100K miles. Severe use can cause the mount to degrade and fail much earlier. (Trivia fact, 996 motor mounts have a 993 part number)
996/997 owners who may not be mechanically adept or have a good understanding of the mechanical or electrical subsystems in their cars could come to the conclusion that if a motor mount failure event happens during lifting the car, that the lifting event is the cause, but the reality is that the mount was doomed well before it failed.
I maintain that if a mount was bound to fail, that it is best that the mount failed when it could draw attention to its condition. Lifting the car using the engine as a mount is a very good way to determine the serviceability of the mounts.
Many 911 owners drive their cars for months if not years with failed mounts and are none the wiser. Their only indication that something may be amiss is an increased level of NVH or that the muffler tips seem to be lower that what they were.
As a part of normal oil change maintenance, I recommend that the condition of the mounts be examined. If there is any purple or dark liquid stains on the mount bottom or the rear engine cross brace, then the mount has failed and needs to be replaced. Replacing a mount is a very easy DIY process.
To replace a mount, simply support the engine with a jack, then remove the bottom bolt securing the mount to the engine, then from the engine bay, remove the 2 top securing bolts, lift the mount out, and drop the new one it and secure it. Note: It is necessary to remove either the air box or secondary air pump to gain access to the mounts. Retail on a replacement mount is about $150, but can be had for less. If you are capable of using a ratchet wrench, you can R&R the mount in under 30 minutes.
The root cause of motor mount failure is simple wear and tear failure. A mount in good repair can handle both positive and negative torsion compression from engine movement, but over time the flexible materials in the mount degrades, and will eventually become brittle and will crack releasing the isolation fluid that is contained in the mount. This is true for not only 996 mounts, but also for mounts from other german manufacturers, especially Audi and VW. Under normal use a mount will usually last about 6-10 years or 100K miles. Severe use can cause the mount to degrade and fail much earlier. (Trivia fact, 996 motor mounts have a 993 part number)
996/997 owners who may not be mechanically adept or have a good understanding of the mechanical or electrical subsystems in their cars could come to the conclusion that if a motor mount failure event happens during lifting the car, that the lifting event is the cause, but the reality is that the mount was doomed well before it failed.
I maintain that if a mount was bound to fail, that it is best that the mount failed when it could draw attention to its condition. Lifting the car using the engine as a mount is a very good way to determine the serviceability of the mounts.
Many 911 owners drive their cars for months if not years with failed mounts and are none the wiser. Their only indication that something may be amiss is an increased level of NVH or that the muffler tips seem to be lower that what they were.
As a part of normal oil change maintenance, I recommend that the condition of the mounts be examined. If there is any purple or dark liquid stains on the mount bottom or the rear engine cross brace, then the mount has failed and needs to be replaced. Replacing a mount is a very easy DIY process.
To replace a mount, simply support the engine with a jack, then remove the bottom bolt securing the mount to the engine, then from the engine bay, remove the 2 top securing bolts, lift the mount out, and drop the new one it and secure it. Note: It is necessary to remove either the air box or secondary air pump to gain access to the mounts. Retail on a replacement mount is about $150, but can be had for less. If you are capable of using a ratchet wrench, you can R&R the mount in under 30 minutes.
I have no idea where you identified my position as "lifting a 911 by the engine is the root and sole cause of motor mount failure". It IS, howver, one of the causes that can easily be eliminated.
01-04-2009, 07:36 PM
#36
Team Owner
If a part--in this case, a motor mount--has become worn due to age and mileage but actually fails when you do something you're specifically not supposed to do--in this case, using it to jack up the entire car--I'm not sure why one would claim that the jacking didn't make the part fail.
It's like continuing to pile snow on your roof beyond its load rating until it caves in and then claiming that the failure was because age had weakened the roof and not because you kept piling weight on it.
When something works for its intended use but fails when used for something that's beyond its intended use, you don't blame the age of the part...you blame yourself for using it beyond its capabilities.
It's like continuing to pile snow on your roof beyond its load rating until it caves in and then claiming that the failure was because age had weakened the roof and not because you kept piling weight on it.
When something works for its intended use but fails when used for something that's beyond its intended use, you don't blame the age of the part...you blame yourself for using it beyond its capabilities.
01-04-2009, 07:40 PM
#37
Race Car
If a part--in this case, a motor mount--has become worn due to age and mileage but actually fails when you do something you're specifically not supposed to do--in this case, using it to jack up the entire car--I'm not sure why one would claim that the jacking didn't make the part fail.
It's like continuing to pile snow on your roof beyond its load rating until it caves in and then claiming that the failure was because age had weakened the roof and not because you kept piling weight on it.
When something works for its intended use but fails when used for something that's beyond its intended use, you don't blame the age of the part...you blame yourself for using it beyond its capabilities.
It's like continuing to pile snow on your roof beyond its load rating until it caves in and then claiming that the failure was because age had weakened the roof and not because you kept piling weight on it.
When something works for its intended use but fails when used for something that's beyond its intended use, you don't blame the age of the part...you blame yourself for using it beyond its capabilities.
Good comments but you won't get through to him because it make too much sense.
01-04-2009, 10:15 PM
#39
Three Wheelin'
So I get the sense that many of you are really stuck on a tangent, so let me recap my points.
1. When changing your 996/997s oil, don't jack up the rear, rather drive the car up on ramps. It is a faster and easier way to gain access to the oil drain and filter, especially for the faint of heart.
2. If you do need to put the rear of the car up on jack stands, then using the engine case centerline to temporarily support the car while you fit jack stands to the rear body support points is perfectly safe, and is done day in and day out on thousands of 996s without any issue.
3. Fluid-filled motor mounts as used on the 996 have a finite life and will fail at some point. If a motor mount is nearing the end of its useful life, using the engine as a lift point may hasten the mount to rupture and a small number of mounts do fail when lifting the car. The OPs experience shows that. However if the mount is in good condition, then there is no reason for concern, as the mount will not be harmed. The shear strength of the mount is identical in both the load and lift modes.
The key point here is that if the mount is nearing the end of its useful life, then there is a 100% probability that it will fail even if the car is never lifted using the engine. Again, if the mount is at the end of its life, it is going to fail regardless if the car is just driven around or lifted using the engine. Don't confuse the catalyst with the end result. How severely the car is operated will determine the life of the mount.
So if you can get past that point and accept the fact that the mounts will fail at some point in time, then you have to ask yourself what is better, to have to mount fail silently and you not know that it has failed, or have it fail in a environment that makes you aware of the failure so that you can remedy the situation quickly?
I would wager that a significant number of the readers of this thread are driving cars with failed mounts right now and are oblivious of the situation. If your mounts have failed, would you not want to be aware of it?
In the end, this whole discussion is probably moot. Those that are on the sheepish side of this discussion would probably never have a need to lift the car up in the rear in the first place and are probably driving around with blown mounts anyway. The other camp that is comfortable in lifting the car from the engine are very well laughing at this much ado nothing.
1. When changing your 996/997s oil, don't jack up the rear, rather drive the car up on ramps. It is a faster and easier way to gain access to the oil drain and filter, especially for the faint of heart.
2. If you do need to put the rear of the car up on jack stands, then using the engine case centerline to temporarily support the car while you fit jack stands to the rear body support points is perfectly safe, and is done day in and day out on thousands of 996s without any issue.
3. Fluid-filled motor mounts as used on the 996 have a finite life and will fail at some point. If a motor mount is nearing the end of its useful life, using the engine as a lift point may hasten the mount to rupture and a small number of mounts do fail when lifting the car. The OPs experience shows that. However if the mount is in good condition, then there is no reason for concern, as the mount will not be harmed. The shear strength of the mount is identical in both the load and lift modes.
The key point here is that if the mount is nearing the end of its useful life, then there is a 100% probability that it will fail even if the car is never lifted using the engine. Again, if the mount is at the end of its life, it is going to fail regardless if the car is just driven around or lifted using the engine. Don't confuse the catalyst with the end result. How severely the car is operated will determine the life of the mount.
So if you can get past that point and accept the fact that the mounts will fail at some point in time, then you have to ask yourself what is better, to have to mount fail silently and you not know that it has failed, or have it fail in a environment that makes you aware of the failure so that you can remedy the situation quickly?
I would wager that a significant number of the readers of this thread are driving cars with failed mounts right now and are oblivious of the situation. If your mounts have failed, would you not want to be aware of it?
In the end, this whole discussion is probably moot. Those that are on the sheepish side of this discussion would probably never have a need to lift the car up in the rear in the first place and are probably driving around with blown mounts anyway. The other camp that is comfortable in lifting the car from the engine are very well laughing at this much ado nothing.
Last edited by Orient Express; 01-04-2009 at 10:49 PM.
01-04-2009, 10:20 PM
#40
Rennlist Member
BTW, when I changed a bulb in my wife's Cayenne today, I couldn't help but laugh at the "Porsche recommends Mobil 1" sticker. Only a fool would say Porsche doesn't recommend a brand of oil right?
01-04-2009, 10:22 PM
#41
Addict
Rennlist Member
Rennlist Member
How often do you change motor mounts ?
01-04-2009, 10:29 PM
#42
Nordschleife Master
The key point here is that if the mount is nearing the end of its useful life, then there is a 100% probability that it will fail even if the car is never lifted using the engine. Again, if the mount is at the end of its life, it is going to fail regardless if the car is just driven around or lifted using the engine. Don't confuse the catalyst with the end result. How severely the car is operated will determine the life of the mount.
I would have given this a shot if I had a shop jack that could reach that point.
01-04-2009, 10:31 PM
#43
Race Car
Last edited by 1999Porsche911; 01-04-2009 at 10:52 PM.
01-04-2009, 10:46 PM
#44
Three Wheelin'
The short answer is as often as necessary. On my personal 996, It is still on its original mounts after 6 years and 70K miles. I expect that I will change them out at about 100K miles. My Audis mounts seem to fail at about that time, so I would expect the 996 to last about as long.
Your mileage may vary. If you drive everyday like you are trying for a new record at the Ring, your mount life (as well as tire, brake, clutch and engine life) will be less. If you drive more conservatively, your mounts will last longer.
Your mileage may vary. If you drive everyday like you are trying for a new record at the Ring, your mount life (as well as tire, brake, clutch and engine life) will be less. If you drive more conservatively, your mounts will last longer.
