New mode of failure for oil system - car out of commission
07-20-2015, 11:15 AM
#16
Three Wheelin'
With washers like that I just get them snug and then it's a matter of feeling them crush, once that happens it's good to go. Not sure how many lbs that is, other than pretty sure it was way less than 37. I sleep well at night.
07-20-2015, 11:16 AM
#17
Race Car
Join Date: Sep 2006
Location: Jacksonville, FL Duval County
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Only tight enough to crush the crush washer.
This is a good demonstration of how applying torque is a very inexact science. What we are trying to achieve is a certain amount of clamping force, but the only way to practically measure it is torque applied. Depending on how much oil is on the plug, and the condition and temperature of the threads, 37 ft-lbs applied can translate into a wide range of clamping forces and stresses on a fastener (or plug in this case). A given torque spec may be safe to apply dry, but actually cause too much stress and yield the fastener when well-lubricated.
This is a good demonstration of how applying torque is a very inexact science. What we are trying to achieve is a certain amount of clamping force, but the only way to practically measure it is torque applied. Depending on how much oil is on the plug, and the condition and temperature of the threads, 37 ft-lbs applied can translate into a wide range of clamping forces and stresses on a fastener (or plug in this case). A given torque spec may be safe to apply dry, but actually cause too much stress and yield the fastener when well-lubricated.
07-20-2015, 11:49 AM
#18
Race Director
07-20-2015, 11:54 AM
#19
Race Director
The factory drain plugs do indeed have this issue, and often have to be replaced every other oil change. I always keep spare drain plugs in my tool box.
When we developed our drain plug, we tested it side by side with an OE plug. We wanted to maintain the factory tightening torque of 37 ft/lbs. We also wanted our plug to be at least as strong as the factory drain plug. We achieved that, and strength tests showed that it fatigued later than the OE plug, but still, no aluminum drain plug is going to last forever when torqued and re-torqued to 37 ft/lbs.
When we developed our drain plug, we tested it side by side with an OE plug. We wanted to maintain the factory tightening torque of 37 ft/lbs. We also wanted our plug to be at least as strong as the factory drain plug. We achieved that, and strength tests showed that it fatigued later than the OE plug, but still, no aluminum drain plug is going to last forever when torqued and re-torqued to 37 ft/lbs.
What killed it was in a pinch I had the oil changed at a quick lube place and the next oil change -- this time at the dealer the tech found the drain plug wrench hole buggered. What happened was the oil change guy didn't insert the tool bit all the way in.
When I did the oil changes one of the things I noticed was how good a fit the tool bit was in the drain plug bit hole. It took a bit of extra attention/effort to make sure the tool bit was fully inserted. With the tool bit fully inserted the force of the loosening or tightening is spread over the entire length of the tool bit hole in the drain plug.
The quick lube guy just put the tool bit in until it met with a bit of resistance and that was that.
Fortunately the tech managed to get the thing out and had a spare for me to use. I ordered extras and when they came in I gave him one to replace the spare he used and I keep at least one new on the car's center console bin for just in case.
07-20-2015, 11:58 AM
#20
Three Wheelin'
07-20-2015, 12:02 PM
#21
Former Vendor
I have to wonder about the skill of the person doing the change. I changed my Boxster's oil a number of times and the same oil drain plug was just fine.
What killed it was in a pinch I had the oil changed at a quick lube place and the next oil change -- this time at the dealer the tech found the drain plug wrench hole buggered. What happened was the oil change guy didn't insert the tool bit all the way in.
When I did the oil changes one of the things I noticed was how good a fit the tool bit was in the drain plug bit hole. It took a bit of extra attention/effort to make sure the tool bit was fully inserted. With the tool bit fully inserted the force of the loosening or tightening is spread over the entire length of the tool bit hole in the drain plug.
The quick lube guy just put the tool bit in until it met with a bit of resistance and that was that.
Fortunately the tech managed to get the thing out and had a spare for me to use. I ordered extras and when they came in I gave him one to replace the spare he used and I keep at least one new on the car's center console bin for just in case.
What killed it was in a pinch I had the oil changed at a quick lube place and the next oil change -- this time at the dealer the tech found the drain plug wrench hole buggered. What happened was the oil change guy didn't insert the tool bit all the way in.
When I did the oil changes one of the things I noticed was how good a fit the tool bit was in the drain plug bit hole. It took a bit of extra attention/effort to make sure the tool bit was fully inserted. With the tool bit fully inserted the force of the loosening or tightening is spread over the entire length of the tool bit hole in the drain plug.
The quick lube guy just put the tool bit in until it met with a bit of resistance and that was that.
Fortunately the tech managed to get the thing out and had a spare for me to use. I ordered extras and when they came in I gave him one to replace the spare he used and I keep at least one new on the car's center console bin for just in case.
07-20-2015, 12:20 PM
#22
And don't bother with the ECS magnetic plug either. After 3 oil changes the soft aluminum was shot and the hex hole rounded. The hole wasn't deep enough to get a good set with the wrench. My tech had to notch it with a dremel and back it out with a screwdriver and mallet
When we developed our drain plug, we tested it side by side with an OE plug. We wanted to maintain the factory tightening torque of 37 ft/lbs. We also wanted our plug to be at least as strong as the factory drain plug. We achieved that, and strength tests showed that it fatigued later than the OE plug, but still, no aluminum drain plug is going to last forever when torqued and re-torqued to 37 ft/lbs.
I found that using generic or cheap hex tools is a recipe for easily rounding a hex nut on any car as the tolerances and design could be on the "loose" side or designed in a way where the edges of the hex is rounded and thus not creating a good grip all the way in the hex hole.
07-20-2015, 12:27 PM
#23
Race Director
The ones I used in my Boxster and Turbo are very hard, purposely so and is very finely finished. The ring is intended to seal by its finish and flatness not by crushing.
Examining a used one finds a very slight depression where the drain plug tightens down on the washer. But it is by no means intended to be crushed like some oil drain plug washers made out of copper or some kind of soft aluminum.
07-20-2015, 02:18 PM
#24
Race Director
Thread Starter
The fact that the plug started leaking about a week ago - a soild two months after my last oil change - suggests to me that the plug is susceptible to cracking when a tensile load is applied and held. The tensile load, plus the cyclic heating/cooling, appears to be sufficient to cause cracking and eventual failure. The leaking oil indicates that the failure was already in progress - attempting to loosen the plug finished the job.
I don't have enough knowledge of the part to know if this is a design weakness, an issue with a single part having an inclusion or other flaw that made it more likely to fail, or user error. I'm fairly fastidious when it comes to maintaining the motor, and I do not belong to the "tighten it until your arm aches" school of thought. Even back in my foolish youth when I DID tend to overtighten stuff, I never saw a failure like this.
Re: finger-tight drain plugs: Never heard of this. Hand-tight for oil filters I'm familiar with, but not with drain plugs...
I don't have enough knowledge of the part to know if this is a design weakness, an issue with a single part having an inclusion or other flaw that made it more likely to fail, or user error. I'm fairly fastidious when it comes to maintaining the motor, and I do not belong to the "tighten it until your arm aches" school of thought. Even back in my foolish youth when I DID tend to overtighten stuff, I never saw a failure like this.
Re: finger-tight drain plugs: Never heard of this. Hand-tight for oil filters I'm familiar with, but not with drain plugs...
07-20-2015, 03:59 PM
#25
Race Director
Thread Starter
...and the owner at Performance hooked me up with an aluminum plug for $5 so I can get the 996 back on the road rather than wait around for a new magnetic plug.
07-20-2015, 04:31 PM
#26
Three Wheelin'
The one in mine looked like it was a crush washer and snugged up like a crush washer and pelican calls it a metal gasket which usually means its a crush washer. If it didn't crush when snug then they wouldn't call for its replacement since if it was "very hard" and "very smooth" it wouldn't ever need to be replaced.
07-20-2015, 04:44 PM
#27
Rennlist Member
If I'm not mistaken, the oil pan and the entire engine case for that matter is aluminum. Needless to mention, the drain plug has to be a softer aluminum in order to be more giving during over-torquing. This way you're replacing the plug vs the pan. So of-course it will need to be replaced priodically regardless of who makes it.
07-20-2015, 05:21 PM
#28
Are you guys using the right washer? The stock washer is soft aluminum that will deform a bit when tightened down to achieve the sealing
http://www.ecstuning.com/ES1376018/
I think the magnetic drain plug is an engineering challenge as I can't imagine the magnet can contract/expand as well as aluminum during all these heat cycles.
http://www.ecstuning.com/ES1376018/
I think the magnetic drain plug is an engineering challenge as I can't imagine the magnet can contract/expand as well as aluminum during all these heat cycles.
07-21-2015, 02:59 AM
#29
Race Director
The one in mine looked like it was a crush washer and snugged up like a crush washer and pelican calls it a metal gasket which usually means its a crush washer. If it didn't crush when snug then they wouldn't call for its replacement since if it was "very hard" and "very smooth" it wouldn't ever need to be replaced.
The ring gets replaced because one of its smooth surfaces is no longer smooth and is at risk of leaking.
Additionally the now deformed and damaged surface is at risk of compromising the sealing surface of the drain plug which is bad enough but at least the drain plug can be replaced. But if the damaged surface of the ring is against the drain pan's sealing surface this can damage this sealing surface and the drain pan can leak. That is a more expensive item to replace.
(The techs tell me they can always tell when the sealing ring has been reused as there is some oil weep sign at the drain plug.)
The ring wants to be replaced every time so both surfaces of the ring are virgin and these virgin surfaces effect an oil tight seal at the drain plug and the oil sump. This works to keep both the drain plug sealing surface and the sump sealing in pristine condition so with a new ring they continue to form an oil tight seal and ensure the drain plug when tightened down is not tipped slightly if it gets on the slight ridge that is formed from the prior use. The drain plug tipped or cocked slightly means the drain plug may not remain tight.
07-21-2015, 10:22 AM
#30
Three Wheelin'
While the sealing ring is hard and finely finished it does deform a bit from use. The drain plug forms a depression into the face it tightens against.
The ring gets replaced because one of its smooth surfaces is no longer smooth and is at risk of leaking.
Additionally the now deformed and damaged surface is at risk of compromising the sealing surface of the drain plug which is bad enough but at least the drain plug can be replaced. But if the damaged surface of the ring is against the drain pan's sealing surface this can damage this sealing surface and the drain pan can leak. That is a more expensive item to replace.
(The techs tell me they can always tell when the sealing ring has been reused as there is some oil weep sign at the drain plug.)
The ring wants to be replaced every time so both surfaces of the ring are virgin and these virgin surfaces effect an oil tight seal at the drain plug and the oil sump. This works to keep both the drain plug sealing surface and the sump sealing in pristine condition so with a new ring they continue to form an oil tight seal and ensure the drain plug when tightened down is not tipped slightly if it gets on the slight ridge that is formed from the prior use. The drain plug tipped or cocked slightly means the drain plug may not remain tight.
The ring gets replaced because one of its smooth surfaces is no longer smooth and is at risk of leaking.
Additionally the now deformed and damaged surface is at risk of compromising the sealing surface of the drain plug which is bad enough but at least the drain plug can be replaced. But if the damaged surface of the ring is against the drain pan's sealing surface this can damage this sealing surface and the drain pan can leak. That is a more expensive item to replace.
(The techs tell me they can always tell when the sealing ring has been reused as there is some oil weep sign at the drain plug.)
The ring wants to be replaced every time so both surfaces of the ring are virgin and these virgin surfaces effect an oil tight seal at the drain plug and the oil sump. This works to keep both the drain plug sealing surface and the sump sealing in pristine condition so with a new ring they continue to form an oil tight seal and ensure the drain plug when tightened down is not tipped slightly if it gets on the slight ridge that is formed from the prior use. The drain plug tipped or cocked slightly means the drain plug may not remain tight.
Lol