LT4 Engine Oil Drain Plug

[Terry M.]

Re: LT4 Engine Oil Drain Plug

Floyd-----


If you get a GM #11562588 you'll have the metric plug with integral seal + MAGNET.

I don't think this plug comes with a magnet any more -- or the part number has changed. I am not sure which, but there is a lot of angst among the C6 community (at least that part of the community that cares) due to the lack of the magnet. Those who care are getting plug(s) from outside GM that includes the magnet. In PRIODUCTION they stopped the magnet in the drain plug during the first month of calendar year 2008. There is no sense changing the topic of this thread to go into the reason for the need for the magnet in newer LS engines.

[Chuck S.]

Re: LT4 Engine Oil Drain Plug

I don't think this plug comes with a magnet any more -- or the part number has changed. I am not sure which, but there is a lot of angst among the C6 community (at least that part of the community that cares) due to the lack of the magnet. Those who care are getting plug(s) from outside GM that includes the magnet. In PRIODUCTION they stopped the magnet in the drain plug during the first month of calendar year 2008. There is no sense changing the topic of this thread to go into the reason for the need for the magnet in newer LS engines.

Wow, that means the magnetic drain plug was OEM for (part of) only one model year, 2007?...I had no idea; I quit frequenting CF before that happened.

If you're just going to get us interested, and then not follow-up with any details about why LS engines need magnets, I guess I'll have to hold my nose and do a little lurking research.

[Terry M.]

Re: LT4 Engine Oil Drain Plug

Yea Chuck -- that was a cheap shot. Sorry. I opened the box, so I guess I should tell everyone what is in it. I just didn’t want to hi-jack this thread. This is Cliff notes version. There is much more, but i would have to kill you, if I told you. On a per centage though, this is not much of a problem, unless of course it happens to you.

One of the "features" of some LS motors (mostly early calendar year 2006 to date, but there have been isolated other examples) is the rocker arms (RA) shed their needle bearings. Often (read: almost always) the first sign of RA failure is needle bearings found on the magnet of the oil drain plug when the oil is changed.

There are two TSBs for this issue. The one for LS7 engines authorizes changing only the failed RA. The one for other LS engines (and not just Corvette engines) authorizes changing ALL the RA when one fails.

Now don't kill the messenger. I am only reporting what I read on the Internet.

If you have the patience to read more (perhaps more than you want to know, but remember you asked) there is a sticky on C6 Corvette Forum at the top of the Z06 part.

[Chuck S.]

Re: LT4 Engine Oil Drain Plug

Yea Chuck -- that was a cheap shot. Sorry. I opened the box, so I guess I should tell everyone what is in it. I just didn’t want to hi-jack this thread. This is Cliff notes version. There is much more, but i would have to kill you, if I told you. On a per centage though, this is not much of a problem, unless of course it happens to you.

One of the "features" of some LS motors (mostly early calendar year 2006 to date, but there have been isolated other examples) is the rocker arms (RA) shed their needle bearings. Often (read: almost always) the first sign of RA failure is needle bearings found on the magnet of the oil drain plug when the oil is changed.

There are two TSBs for this issue. The one for LS7 engines authorizes changing only the failed RA. The one for other LS engines (and not just Corvette engines) authorizes changing ALL the RA when one fails.

Now don't kill the messenger. I am only reporting what I read on the Internet.

If you have the patience to read more (perhaps more than you want to know, but remember you asked) there is a sticky on C6 Corvette Forum at the top of the Z06 part.

Some of the owners were complaining of excessive rocker arm noise on early C6s...I suspect the engineers now know the noise was real, and a symptom of incipient failure.

I'll have to do some more study on this news. Since I have a very early 2006 (9/05), I'm interested in determining if the problem is simply a mileage dependent design flaw, or the result of using the car like it was intended to be used. My car would probably never meet either of those criteria.

So, the magnets were discontinued because they tipped the owners to the failure? Personally, I never could see much benefit from the magnets anyway; I think it's more of a placebo for anxious owners. (I'm sure Joe's in total disagreement. )

Think about it...the area of that magnet tip is probably less than 0.15 square inches, and the magnet is low power...iron particles in every milliliter of oil would have to come in virtual contact with that magnet to stick. Not to mention every milliliter of that oil is being filtered through a micron rated filter every time it's used.

I changed mine to the magnet style drain plug, but I never find much of anything on the magnet...maybe if I ran the everlivin' h*** out of it. As demonstrated in the case you cited, once you find significant iron filings on your magnetic drain plug, you already have a big problem.

[Terry M.]

Re: LT4 Engine Oil Drain Plug

Some of the owners were complaining of excessive rocker arm noise on early C6s...I suspect the engineers now know the noise was real, and a symptom of incipient failure.

I'll have to do some more study on this news. Since I have a very early 2006 (9/05), I'm interested in determining if the problem is simply a mileage dependent design flaw, or the result of using the car like it was intended to be used. My car would probably never meet either of those criteria.

So, the magnets were discontinued because they tipped the owners to the failure? Personally, I never could see much benefit from the magnets anyway; I think it's more of a placebo for anxious owners. (I'm sure Joe's in total disagreement. )

Think about it...the area of that magnet tip is probably less than 0.15 square inches, and the magnet is low power...iron particles in every milliliter of oil would have to come in virtual contact with that magnet to stick. Not to mention every milliliter of that oil is being filtered through a micron rated filter every time it's used.

I changed mine to the magnet style drain plug, but I never find much of anything on the magnet...maybe if I ran the everlivin' h*** out of it. As demonstrated in the case you cited, once you find significant iron filings on your magnetic drain plug, you already have a big problem.

I can not tell you why the magnet(s) was(were) discontinued in PRODUCTION, however, my guess is a combination of cost and the fact that minor accumulations of iron filings were alarming owners needlessly lead to the discontinuance. LS7 has two drain plugs. LS2 & 3 have one. With the 2010 Grand Sport production that division is blurred a lot, but that is another story.

A close read of that thread on CF, ignoring the posts of alarmists as best you can, doesn't show a trend toward hard use being a factor -- at least as I read it. It seems to me as many self-described aggressive drivers as moderate drivers have had issues.

I personally drain the oil into an auxiliary pan so that if I find any needles on the magnet I can check the rest of the used oil for needles -- count them -- before the oil is dumped into the larger container for proper disposal. It seems to me, considering the potential need to not lose needles (however slight) it is worth having the magnets. However, I got in under the wire with my build in the Fall of 2007. If my LS engine was built without a magnet, I would seek out a replacement with a magnet.

If I were forced to rely on others to change the oil, I might believe differently -- since I doubt one could convince many "professionals" of the need to check for needles on a magnet, or if found to check the drained oil for more needles.

[Joe L.]

Re: LT4 Engine Oil Drain Plug

Joe, for those that don't want to buy a plug each time the seal gets tired, that seal is replaceable...at least it is on my 2006 LS2.

The seal is not an circular section o-ring, but is like a square section ring gasket (similar to a water hose gasket) with a semi-circular o-ring section molded to one face as a contact surface. You dig the old seal out of the groove, and press the new seal into place, and it stays. I purchased a couple of those seals early, but they came in a plain plastic bag...no part number.

Your picture of the elastomer seal washer used on LT1s reminded me that my later 87 with aluminum heads had that type drain plug seal when I bought it. The car had been owned by a Corvette afficianado however; if the seal could be interchanged with the nylon washer, he could have made that change himself.

Chuck-----


Yes, I have found the seal is available separately under GM #3536966. It carries a GM list price of about 2 bucks. The complete plug+seal I mentioned, GM #11562588, carries a list price of about 6 bucks. I have found that these seals will last multiple oil drains (unlike the nylon and composition seals). Rightly or wrongly, I just have the feeling that the factory-assembled piece might have a very slight chance of sealing better. So, I'll pay the 4 buck "premium" every few years and go with the complete assembly.

The original seal on my 2004 Grand Prix still seals perfectly after many oil drains------not even the slightest sign of an oil film around the plug.

[Pat M.]

Re: LT4 Engine Oil Drain Plug

I've never personally changed the oil in my LT4, but it must have the integral seal, because I can see it doesn't have the nylon bushing, and it's never leaked a drop.

[Floyd B.]

Re: LT4 Engine Oil Drain Plug

I picked up a new drain plug bolt - part #11562588 and can confirm that it no longer includes a magnate. I also bought 2 seals - part #3536966. I cannot see how the performance of the plug will be compromised by replacing the seal. The original seal is not attached to the bolt in any way - it simply slips on/off. I think the best solution is to replace the seal every so often. I paid MSRP of $2.14 for the seals; You can get a package of 10 seals for $12.70 from GMPartsDirect; that's $1.27 per.

[Chuck S.]

Re: LT4 Engine Oil Drain Plug

I picked up a new drain plug bolt - part #11562588 and can confirm that it no longer includes a magnate. I also bought 2 seals - part #3536966. I cannot see how the performance of the plug will be compromised by replacing the seal. The original seal is not attached to the bolt in any way - it simply slips on/off. I think the best solution is to replace the seal every so often. I paid MSRP of $2.14 for the seals; You can get a package of 10 seals for $12.70 from GMPartsDirect; that's $1.27 per.

Good choice IMO...the plug and the seal are manufactured separately and must be assembled. There is no evidence I could see that anything like adhesive is used to retain the seal in the groove. I figure I can stick that seal in the groove as well as a body at the factory. Reuse, recycle, conserve...it's totally green.

Of course, ten seals would be about a 30 year supply.

[Joe L.]

Re: LT4 Engine Oil Drain Plug

I picked up a new drain plug bolt - part #11562588 and can confirm that it no longer includes a magnate. I also bought 2 seals - part #3536966. I cannot see how the performance of the plug will be compromised by replacing the seal. The original seal is not attached to the bolt in any way - it simply slips on/off. I think the best solution is to replace the seal every so often. I paid MSRP of $2.14 for the seals; You can get a package of 10 seals for $12.70 from GMPartsDirect; that's $1.27 per.

Floyd-----

Good information and it saves me the trouble of buying one of these to confirm configuration. Apparently, what's happened here is that GM replaced the magnet type drain plug with a non-magnetic piece. That's unusual. Usually, in a case like this, they would just discontinue the magnetic plug without supercession since the replacement is not functionally equivalent. However, in this case, I presume that the magnetic plug must have been originally installed for some applications, so they had to do a supercession.

No problem, though, if one wants a magnetic plug. Dorman/Motormite will sell you all you want under their number 090-091. From what I can tell, the configuration is virtually the same as GM.

As far as replacing the seal on a drain plug, I originally had the notion that the seal was in some way bonded to the plug and that was part of the reason it sealed so well. It sounds like it's not bonded, though. I'll have to look closer at one.

[Terry M.]

Re: LT4 Engine Oil Drain Plug

Of course, ten seals would be about a 30 year supply.

That depends on what is in your fleet. For some folks ten seals might not last long at all.

[Chuck S.]

Re: LT4 Engine Oil Drain Plug

As far as replacing the seal on a drain plug, I originally had the notion that the seal was in some way bonded to the plug and that was part of the reason it sealed so well. It sounds like it's not bonded, though. I'll have to look closer at one.

Joe, Floyd's comment that it "simply slips on and off" made me question my recall and take another look at the one from my 2006 (no magnet).

I remembered the seal as fitting into a groove recess, but actually the sealing face of the plug has a slight recess (counterbore?) the full diameter of the seal. The seal is like a circular section O-ring about 0.080" diameter, but with a "web" molded into the center.

There is a hole in the center of the "web" about the same as the minor diameter of the threaded portion, causing the seal to be captured on the threads. When the plug is tightened, the seal effectively compresses like an O-ring, but without the full support of an O-ring groove. Since there isn't any pressure to be sealed, a true O-ring isn't necessary as long you have some slight compression remaining in the seal.

[Floyd B.]

Re: LT4 Engine Oil Drain Plug

Joe, Floyd's comment that it "simply slips on and off" made me question my recall and take another look at the one from my 2006 (no magnet).

I remembered the seal as fitting into a groove recess, but actually the sealing face of the plug has a slight recess (counterbore?) the full diameter of the seal. The seal is like a circular section O-ring about 0.080" diameter, but with a "web" molded into the center.

There is a hole in the center of the "web" about the same as the minor diameter of the threaded portion, causing the seal to be captured on the threads. When the plug is tightened, the seal effectively compresses like an O-ring, but without the full support of an O-ring groove. Since there isn't any pressure to be sealed, a true O-ring isn't necessary as long you have some slight compression remaining in the seal.

Yep. Both the original on my LT4 and the replacement I bought today are exactly as you describe.

[Joe L.]

Re: LT4 Engine Oil Drain Plug

Joe, Floyd's comment that it "simply slips on and off" made me question my recall and take another look at the one from my 2006 (no magnet).

I remembered the seal as fitting into a groove recess, but actually the sealing face of the plug has a slight recess (counterbore?) the full diameter of the seal. The seal is like a circular section O-ring about 0.080" diameter, but with a "web" molded into the center.

There is a hole in the center of the "web" about the same as the minor diameter of the threaded portion, causing the seal to be captured on the threads. When the plug is tightened, the seal effectively compresses like an O-ring, but without the full support of an O-ring groove. Since there isn't any pressure to be sealed, a true O-ring isn't necessary as long you have some slight compression remaining in the seal.

Chuck------


I think one of the "keys" to the sealing efficiency of this design lies in the fact that the seal fits into the recess in the plug. Therefore, when the plug is tightened the compression on the seal is limited to that which can occur before the peripheral edge of the plug contacts the oil pan. With accurate manufacture of the plug and seal, this provides for near-perfect control of compression of the seal. In conjunction with the seal design and material, that, in turn, provides for superior sealing.

I just wish they made this design in a 1/2-20 thread size for earlier engines. If they do, I have not been able to find one, either GM or aftermarket.

[Joe L.]

Re: LT4 Engine Oil Drain Plug

I picked up a new drain plug bolt - part #11562588 and can confirm that it no longer includes a magnate. I also bought 2 seals - part #3536966. I cannot see how the performance of the plug will be compromised by replacing the seal. The original seal is not attached to the bolt in any way - it simply slips on/off. I think the best solution is to replace the seal every so often. I paid MSRP of $2.14 for the seals; You can get a package of 10 seals for $12.70 from GMPartsDirect; that's $1.27 per.

Floyd------


By the way, I initially thought that the 11562588 was a magnetic plug since it replaced a plug that I know to be magnetic. However, you've now confirmed that it is not magnetic. I've now pretty much determined that there is no magnetic plug available from GM in the 12 mm thread size with or without the new style seal. There were once several different such plugs but now there are none.

Generally, GM has offered a magnetic plug at least as a SERVICE item for many years. However, they have now, apparently, chosen to no longer offer one for the 12 mm thread size. Certainly, they would have no problem sourcing such a plug if they chose to offer it in SERVICE.

So, this all implies that, perhaps, they have a good reason for discontinuing any PRODUCTION use of a 12 mm magnetic plug and also discontinuing to even offer it in SERVICE. They still do offer in SERVICE such a plug in the 1/2-20 thread size. But, all using that size are older applications that are long-since out of warranty. However, I do not believe that the elimination of the magnetic drain plugs for 12 mm applications has anything to do with any sort of attempt to conceal engine problems from the owner (i.e. roller bearings from the rocker arms, etc.). I just do not believe that GM would do anything like that. What the elimination of the magnetic drain plugs implies to me is that there was some sort of problem created by these plugs. I've always figured that there was not a great amount of good that these plugs could do, but I figured there was no harm, either. Maybe there was a flaw in my "figuring". Perhaps, rather than trying to find a way to obtain a magnetic plug, we should "take a cue" from GM's elimination of them.


As I mentioned previously, if one does want to use a 12 mm thread size magnetic plug with new style seal, it's easy to get one as manufactured by Dorman.