Onan generator oil change

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driftless shifter said:
I'd be concerned these cut outs you speak of weren't actually cracked aluminum casting. There is a jerry rig fix using high quality epoxy and a pipe nipple with a new drain plug at the end of the nipple..

Bill

I agree. What I'd do is get a stainless nipple about 1 inch long, measure how many threads are showing when inserted. Then take it back out cut the end off so it doesn't go in too far. Clean all the oil from the threaded area and insert the nipple using red locktite . Let it dry and install a brass valve on the nipple with a plug to remove to change the oil. The locktite will bond the aluminum case and stainless together. It can be removed if needed with a little heat on the nipple.
 
92GA said:
I agree. What I'd do is get a stainless nipple about 1 inch long, measure how many threads are showing when inserted. Then take it back out cut the end off so it doesn't go in too far. Clean all the oil from the threaded area and insert the nipple using red locktite . Let it dry and install a brass valve on the nipple with a plug to remove to change the oil. The locktite will bond the aluminum case and stainless together. It can be removed if needed with a little heat on the nipple.

You could locktite one of these:  http://www.amazon.com/Milton-Industries-Inc-S-614-4-4-Inch/dp/B000HEITXE/ref=sr_1_1?s=automotive&ie=UTF8&qid=1421627988&sr=1-1&pebp=1421628038876&peasin=B000HEITXE
 
driftless shifter said:
I'd be concerned these cut outs you speak of weren't actually cracked aluminum casting. There is a jerry rig fix using high quality epoxy and a pipe nipple with a new drain plug at the end of the nipple..

Bill

Luckily, they aren't!  ;D  They are maybe 1/8" wide and 1/3" tall, and 180 degrees apart, and I'm pretty sure that they are there to allow ALL of the oil in the pan to drain out...without them, the final 1/3" of oil in the pan could not escape out the drain hole. Just picture how you or I would design a drain...with all of the threads BELOW the level of the bottom of the oil pan, such that when you remove the plug ALL of the oil comes out of the oil pan. Then picture trying to design it such that 2/3 of the drain hole threads are ABOVE the level of the bottom of the oil pan...you'd have to somehow provide a path for the oil to get past those threads that are above the level of the bottom of the oil pan, and Onan's way was to provide those two "cut-outs". I still haven't figured out why on earth they had to design it that way...it isn't like there is a clearance issue below the oil pan...there would have been plenty of room to design it with all of the threads below the level of the bottom of the oil pan.
 
Rene T said:
You could locktite one of these:  http://www.amazon.com/Milton-Industries-Inc-S-614-4-4-Inch/dp/B000HEITXE/ref=sr_1_1?s=automotive&ie=UTF8&qid=1421627988&sr=1-1&pebp=1421628038876&peasin=B000HEITXE

Yes...apparently that one has no O-rings, so it should work OK for oil and heat. It would have to be cut off such that only 3 threads were being engaged, in order for the oil to be able to full drain out of the oil pan (see my other post regarding that topic).

Hate to lose the full diameter of the original drain plug, but at this point, knowing that in reality only 3 threads (and aluminum, at that) are seriously hanging onto the drain plug, I do want to semi-permanently install a 1/4"-14 NPT SOMETHING, using thread sealant/loctite AND a metal washer and gasket, and then never remove it again. Might have to experiment with various thicknesses of washers and gaskets to get the right combination because of what Rene T had mentioned: "you would want the flange to make contact with the gasket at the same time you ended up with 100% thread engagement." I still need to call Onan and find out about the drain plug change that happened starting with SPEC L, which changed to a drain plug with a washer/gasket......the oil pan part number remained the same, so likely it still has a tapered threaded hole, and so perhaps they designed a drain plug/washer/gasket combination that achieves what Rene T is referring to, above. However, with just 3 aluminum threads hanging onto the plug, I'd still prefer Rene T's semi-permanent solution, and just never have to remove/replace that plug again, ever.

Another option would be to get the new updated Onan drain plug with washer/gasket, assuming it solves the problem, and then Loctite it in, and then just use a suction pump to pull the oil out of the dipstick/fill hole when I do oil changes from now on, but I'd rather have a better overall solution for the next owner of this thing. With Rene T's drain cock or the other suggested nipple approach, future owners would then have the option of doing either the drain cock or the suction method for oil changes. I don't know if the suction method is as effective at removing any crud from the bottom of the oil pan as draining is, or not.

Onan's use of tapered threads would have been fine if they had just designed the oil pan such that ALL of the threads were below the level of the bottom of the oil pan, eliminating the need for the "cut-outs", but they didn't do that, and so we are left, in reality, with just 3 aluminum threads to depend upon (and only 3 useable threads if the semi-permanent solution is used), which aren't enough, IMHO. Onan compounded the problem by specifying 21 lbs-ft of torque in the Operator's manuals, despite the fact that the Service manuals ('97 and '06, anyway) specify 5-8 lbs-ft. The "cut-outs" aren't cracks, but it wouldn't surprise me at all if 21 lbs-ft of torque did, indeed, SPREAD the upper 2/3 of the drain hole threads where the cutouts are, rendering them mostly useless as far as their ability to aid in holding the drain plug in place, and I'm surprised that that amount of torque hasn't completely stripped ALL of the threads...21 lbs-ft still seems too high for aluminum, as others have also commented.
 
92GA said:
I agree. What I'd do is get a stainless nipple about 1 inch long, measure how many threads are showing when inserted. Then take it back out cut the end off so it doesn't go in too far. Clean all the oil from the threaded area and insert the nipple using red locktite . Let it dry and install a brass valve on the nipple with a plug to remove to change the oil. The locktite will bond the aluminum case and stainless together. It can be removed if needed with a little heat on the nipple.

My oil pan is not cracked (yet), but, yes, I think that I get what you are saying here...and it would work even better if Onan hadn't designed the drain hole with 2/3 of the threads above the bottom of the oil pan, necessitating the "cut-outs". UNFORTUNATELY, because of Onan's design, ANYTHING that is going to remain in the drain hole during oil draining can only occupy the bottom 3 threads if a complete oil drain is desired...otherwise you'd leave approx. 1/3" of oil in the pan because the "cut-outs" would be blocked. 3 threads might be enough, especially if sealant/Loctite is used, and it might be worth trying just to avoid having to ever remove/replace anything from that drain hole again, risking stripping the aluminum threads and/or spreading the upper cut-out 2/3 of the threads apart to the point that they might even break off in the oil pan...I don't know how well attached they are in there.

If Rene T's drain cock has enough threads on it to achieve the same tight fit as the nipple above would, without bottoming out on the hex head on the drain cock, the ideal setup would then be the drain cock, cut down so that only 3 threads are being engaged into the oil pan hole, semi-permanently "glued" into place with sealant AND using a washer/gasket combination (as insurance against leakage). I'll have to spend some time at hardware and/or auto supply stores this week to see if I can find a drain cock or anything else made of brass (or steel???) in 1/4"-14 NPT that has enough threads and/or space near the bolt head to allow for 3 tight fitting threads AND a washer/gasket under the bolt head, keeping in mind what Rene T had mentioned: "you would want the flange to make contact with the gasket at the same time you ended up with 100% thread engagement." Hopefully, if I spend enough time in stores I can find something that will satisfy all of the above requirements and I won't have to worry about damaging my oil pan ever again. If nothing else can be found that is more convenient, then I'll go with the nipple method. I've even thought about getting a suction device to just remove the oil out through the dipstick/fill hole, but I'd still want to have a workable drain option because the next owner might want to go that route and I wouldn't want to have to tell him that if he removes the drain plug he might have headaches trying to replace it without causing damage or having it leak. Something that is installed semi-permanently into those 3 good available threads will prevent those potential problems and still allow for complete draining of the oil in the oil pan, if/when a suction device is not used.

I was wondering about the choice of stainless steel vs. brass for the nipple...you had stated "The Loctite will bond the aluminum case and stainless together"...is the Loctite able to bond better to steel than to brass, and if so, would it matter if it was stainless steel or just steel? I'm also wondering if I could use blue Loctite instead of red, to make possible future removal easier? Or is there a sealant out there that both seals and bonds that would do those two jobs better than Loctite?

Thanks to everyone for your help with all of this. My ALL CAPS comment to Brad (who said "sorry for derailing..." and then proceeded to derail) was just frustration with constantly having to wade through off-topic posts to find the on-topic posts that might actually help with the problem being researched. Yes, off-topic posts can be educational, too, and if I had unlimited time I would love to read all of them, but I'm trying to get my MH ready for a 1000 mile trip with my 91 year old frail mother aboard to move us to where my brother moved to, and need to get my MH quickly into great, safe condition...and I'm having to do this while serving as a nearly full-time caregiver to my mother, who lives with me. I haven't really had a day off in over a year, and so my patience is pretty thin. Perhaps I could have not used ALL CAPS, but I still believe that if everyone just stuck to the topic of the thread, it would make for a more efficient forum. Yeah, I know...I'm not on topic here...hypocrite, right?...but since this can was already opened, I thought I should explain, and also I wanted to make sure that no one thought I was addressing Gary with my ALL CAPS comment. I quoted Brad's derailing post, but since my ALL CAPS comment appeared right after Gary's post some people might have thought that I was addressing Gary's comment instead of Brad's. Part of the problem is that, in this forum, posts seem to appear chronologically regardless of whose comment you are replying to and quoting, as opposed to some other forums where your reply to a person's post appears as a sub-post to their post. There are good things to be said for both styles, though.
 
I'm not buying the reasoning for the "drain" slots in the threads. The difference in the amount of oil with or without the slots would be a couple table spoons of oil. Engineers wouldn't be concerned about a couple tablespoons remaining in the sump. Maybe they are thread chasers to clean the threads as they go back in so grimy drain plugs don't ruin threads or introduce grit to the sump. I'm thinking someone lost the original flanged drain plug, with crush washer, or something. Just because you only see three complete threads doesn't mean that the slotted portion doesn't have any holding strength I have seen slotted threads in many applications. Wheel bearing spindles often have a large slot machined into them for locking tabs for one example. Does the face of the drain hole have a machined flat surface? If it does it is meant as a sealing surface.

Bill
 
Soyjer,
I just googled "2002 onan microlite" found a manual. your drain plug is supposed to be flanged and have a gasket.

http://www.cumminsonan.com/www/pdf/manuals/981-0503.pdf

Figure 10-2, page 10-2.

Bill
 
Gary RV Roamer said:
Yeah, you would want a fat, soft gasket with that set-up, so that it fills the gap as you could compress the gasket.

Here is a brass plug with enough flange to seat a washer/gasket. Don't need much since its an almost zero pressure application.
http://www.zoro.com/i/G5123176/?category=5764

Or get somebody to weld a flange on a standard pipe plug.  8)
Gary, I think if you wrap some Teflon tap at the top where it engages the last 3-4 threads on the pan it will seal. I know they say use the paste but I think that is a cya statement because of the slotted threads would possibly cut off the tape if wrapped all the way down the plug. Just wrap the plug at the top where it will engage the solid threads.
I would also look at the parts list for the later plugs with a flange and just order one if they are the same pipe thread.
Billl
 
Carefully applied teflon tape could certainly work, but it wouldn't take much of a slip-up to get some bits of tape floating around in the sump. Teflon cuts or shreds easily and forms little slivers of plastic that could easily end up in an oil gallery and clogging it. Ordering the right size Onan oil plug seems like the best alternative. Or maybe a Fumoto-style oil drain valve instead.

I checked the Fumoto web site and they show only 1/4" and 3/8" NPT valves for Onans. The size closest to 1/2" is a 12mm pipe thread.
http://www.fumotousa.com/results.php?make=64&year=9999&model=28985&makeid=ONAN&modelid=Onan+engines+with+12mm-1.75+plug
 
I agree Gary. I am not a fan of the Fumoto valve as it seams to prevent complete draining of the old oil.
One other way to seal the threads you could use a couple of drops of Loctite. If you use the blue/removable it will seal the threads and you don't have to worry about the plug vibrating loose.  ;D Just don't use the red.
Bill
 
Chances are that if the plug does indeed utilize a gasket, the chances are the threads are not a NPT/Pipe thread but instead a straight thread like maybe a 1/2"-20. Someone may have thrown a pipe plug in there because they thought it was the correct fitting for that hole. A call to the manufacturer should solve the question as to what actually belongs there. If it is a straight thread, hopefully the existing threads are not destroyed to the point where they can't be used. If you look at all the fittings that Gary suggested, I think they are ALL straight threads not pipe/tapered where they screw into the pan.
 
driftless shifter said:
I'm not buying the reasoning for the "drain" slots in the threads. The difference in the amount of oil with or without the slots would be a couple table spoons of oil. Engineers wouldn't be concerned about a couple tablespoons remaining in the sump. Maybe they are thread chasers to clean the threads as they go back in so grimy drain plugs don't ruin threads or introduce grit to the sump. I'm thinking someone lost the original flanged drain plug, with crush washer, or something. Just because you only see three complete threads doesn't mean that the slotted portion doesn't have any holding strength I have seen slotted threads in many applications. Wheel bearing spindles often have a large slot machined into them for locking tabs for one example. Does the face of the drain hole have a machined flat surface? If it does it is meant as a sealing surface.


Bill

I'm not sure I agree about the purpose of the cutouts...they are 1/3" tall, and 1/3" is a lot of oil and crud to leave in the oil pan each oil change.

I agree with your logic regarding the machined surface...makes perfect sense...doesn't explain why a tapered NPT thread was used, but maybe they wanted to create a seal in two ways...who knows? And yes, the drain hole face DOES have a machined flat surface approx. 1/8" wide, but the exploded parts diagram in the Parts manual shows a drain plug...part # 502-0153...WITHOUT a washer of any kind, and when i look at the picture of the 502-0153 drain plug I can see that it matches my drain plug in NOT having any kind of flange on it:

http://www.randkproducts.com/onan-5020153-drain-plug-p-686.html?osCsid=m3joao5s1a06r5ehojl72remt5

However, my generator is a SPEC K model, and the SPEC L model DOES come with a different plug (hopefully flanged) AND A WASHER (part numbers 181-0489 and 181-0490). I called the regional Cummins-Onan center and spoke to two gentlemen there including an experienced Onan engineer, and neither of them had a clue as to any of this, couldn't tell me if the SPEC L plug/washer would work in the SPEC K oil pan, etc. I mentioned that the oil pan part number 102-1444 did NOT change from SPEC K to SPEC L, and so it would seem that they must be exactly the same, but the engineer just said that the vendor might have changed and that he couldn't guarantee that the threads hadn't changed, etc. He swore that the threads were not NPT tapered until I "showed" him the description in the Parts manual which clearly says 1/4-14 NPT. They also didn't know why the Operator's manuals specify 21 lbs-ft and the Service manuals ('97 and '06 were the ones that I could find to look at) specify 5-8 lbs-ft., and didn't seem to be bothered by it. Basically, I got the impression that they really only support dealers, and if you are trying to do anything yourself, including oil changes, you are just on your own, and if the torque value in the Operator's manual is 3x the correct value shown in the Service manuals and you strip out or crack your oil pan...oh well, we'll be happy to sell you a new one.

Yes, I could just order the SPEC L drain plug and washer and see if it fits and solves the problem...and it probably would. I just wish that I could have received an answer from Onan on this such as "we have an improved drain plug with washer that will fit into your existing oil base and solve your leaking problem, and the reason that we publish a different torque value in our Operator's manuals than in our Service manuals is because ________________, OR, we were unaware of this contradiction, and we will immediately notify owners not to torque according to the 21 lbs-ft shown in their Operator's manuals". I still don't get how this could have existed for over a decade and nobody at Onan became aware of it or tried to correct it. I'm not cynical enough to believe it was anything other than an honest mistake, but how could they not know about it, nor try to correct it?...I don't get it.
 
Gary RV Roamer said:
Carefully applied teflon tape could certainly work, but it wouldn't take much of a slip-up to get some bits of tape floating around in the sump. Teflon cuts or shreds easily and forms little slivers of plastic that could easily end up in an oil gallery and clogging it. Ordering the right size Onan oil plug seems like the best alternative. Or maybe a Fumoto-style oil drain valve instead.

I checked the Fumoto web site and they show only 1/4" and 3/8" NPT valves for Onans. The size closest to 1/2" is a 12mm pipe thread.
http://www.fumotousa.com/results.php?make=64&year=9999&model=28985&makeid=ONAN&modelid=Onan+engines+with+12mm-1.75+plug

According to the Parts manual, this is 1/4"-14 NPT, and when holding it up against a known 1/4"-14 NPT, it looks identical, so the Fumoto might be an option, if it would work otherwise.
 
Rene T said:
Chances are that if the plug does indeed utilize a gasket, the chances are the threads are not a NPT/Pipe thread but instead a straight thread like maybe a 1/2"-20. Someone may have thrown a pipe plug in there because they thought it was the correct fitting for that hole. A call to the manufacturer should solve the question as to what actually belongs there. If it is a straight thread, hopefully the existing threads are not destroyed to the point where they can't be used. If you look at all the fittings that Gary suggested, I think they are ALL straight threads not pipe/tapered where they screw into the pan.

According to the Parts manual, this is 1/4"-14 NPT, and when holding it up against a known 1/4"-14 NPT, it looks identical, and it matches the picture for the correct part number. See my other post regarding the change in plugs that occurred with SPEC L and my waste-of-time call to Onan.  :-[
 
Soyjer,
Using the serial number provided by you earlier in this thread you have a KY spec K. Can't find a replacement drain plug but do find a nylon washer for the drain plug. It is supposed to be 1/2" ID I would go to an auto parts store and pick up a couple different 1/2" diameter drain plugs of different dimensions and thread count even metric and SAE, take them home and find one the fits threads properly, return the rest. My guess is some one lost the proper drain plug and replaced it with the pipe thread plug. You will probably get lucky and the threads won't be terribly mucked up and everything will seal with the proper plug and washer. Have seen similar mistakes in the aircooled VW oil sender example I mentioned in an earlier response turn out OK, when proper part was put back in.

This is how I would proceed were it me.

Bill
 
driftless shifter said:
Soyjer,
Using the serial number provided by you earlier in this thread you have a KY spec K. Can't find a replacement drain plug but do find a nylon washer for the drain plug. It is supposed to be 1/2" ID I would go to an auto parts store and pick up a couple different 1/2" diameter drain plugs of different dimensions and thread count even metric and SAE, take them home and find one the fits threads properly, return the rest. My guess is some one lost the proper drain plug and replaced it with the pipe thread plug. You will probably get lucky and the threads won't be terribly mucked up and everything will seal with the proper plug and washer. Have seen similar mistakes in the aircooled VW oil sender example I mentioned in an earlier response turn out OK, when proper part was put back in.

This is how I would proceed were it me.

Bill

Yes, mine is a SPEC K, and it has the original drain plug...the SPEC B THRU K drain plug which has no flange, and no washer. If I can't find the SPEC L flanged drain plug and washer 181-0489 and 181-0490, I'll search stores locally to find either the equivalent or a drain cock solution (see other posts). The problem with trying to find an equivalent is the issue that Rene T spoke of "you would want the flange to make contact with the gasket at the same time you ended up with 100% thread engagement."...this is an issue because Onan used 1/4"-14 NPT TAPERED thread. Hopefully, Onan found the right combination of washer thickness and thread engagement at proper torque to solve this problem in their updated SPEC L flanged drain plug and washer 181-0489 and 181-0490 ($14 for the pair)....I'll see if I can find those parts somewhere, today, and hope that the new flanged plug 181-0489 can be tightened to 5-8 lbs-ft AND simultaneously properly compress the gasket/washer 181-0490. The parts description just says "washer" for the 181-0490...I'm assuming that it is a compressible washer/gasket of some sort, and not just a metal washer. Bugs me to have to pay $14 + (probably) shipping for a drain plug and washer that should have been designed properly in the first place, but that seems to be the norm with most products, nowadays.

Update: I just spoke to a very helpful woman at Onan at 1-800-888-6626....she said that the new 181-0489 and 181-0490 plug/washer WILL fit into my older SPEC K oil base...whew. She also checked the latest 2012 and 2013 Operator's and Service manuals and verified that the Operators' manuals STILL disagree with the Service manuals (has been true since at least 2002 and likely way before that) regarding torque values for the drain plug, and then she asked an engineer and he verified that the Service manual's 5-8 lbs-ft is the correct value, and the Operator's manual's 21 lbs-ft is incorrect. She started a Help ticket to get this error corrected starting with the next printing of Operator's manuals.

She also said that the 2010 Parts manual is wrong...the 181-0489 is the washer and the 181-0490 is the new drain plug, not the other way around as the Parts manual indicates.

www.cumminsonan.com/www/html/Common/pdf/manuals/981-0246.pdf
 
I'll bet any decent NAPA store could come up with a 1/4" NPT oil drain plug (with flange). Even Amazon has them:
http://www.amazon.com/Industrial-Magnetic-Stainless-Plug-External/dp/B002A378PU#productDetails
 
Gary RV Roamer said:
I'll bet any decent NAPA store could come up with a 1/4" NPT oil drain plug (with flange). Even Amazon has them:
http://www.amazon.com/Industrial-Magnetic-Stainless-Plug-External/dp/B002A378PU#productDetails

Yes, I'm going to try to order the new improved Onan drain plug and "washer", but in the meantime I'll see what I can find at NAPA, Home Depot, Ace, Autozone, etc. But it has to be 1/4"-14 NPT, and I'm going to require that it have the flange and compressible gasket/washer like the new updated Onan one does, or at least room for a metal washer and a compressible gasket/washer, and so the hard part is meeting the "you would want the flange to make contact with the gasket at the same time you ended up with 100% thread engagement" requirement. It just has to have enough threads on it or overall length so that when it tightens up it still has room under the head or flange for the compressible gasket/washer, etc. Too many threads or too long I can live with cuz I can just fill in the space with more washers, but too little room would cause the  threads to not be fully engaged, and although maybe the gasket alone would keep it from leaking, I'd be afraid that it might back out with vibration, and I actually would prefer to have the double-seal insurance of both the gasket seal AND the tapered thread seal, if possible.

Rene T's drain cock idea was attractive and normally would be a good idea, but because Onan's cut-outs it would be hanging on by only 3 threads, and that makes me nervous. I applied 17 lbs-ft of torque to my plug...and then stopped because it felt WAY wrong...before I learned that the Operators manual was incorrect and it should say 5-8 lbs-ft like the Service manuals do, and so if whatever new plug I buy doesn't feel right when I install it...in other words if the 17 lbs-ft already has messed up my oil pan hole, I'll just make it a semi-permanent installation and use a suction device to remove the oil from the dipstick/fill hole from now on.
 
pull the pan and take it to a welding or machine shop.  they could change it to whatever thread you want!
 
blw2 said:
pull the pan and take it to a welding or machine shop.  they could change it to whatever thread you want!

Yeah...if you own an RV, being rich would help...I'm learning that.

I'd love to know why Onan designed the drain plug hole that way (above the bottom of the oil pan, requiring the cut-outs). I could see it if clearance was an issue, but this generator has about an inch of empty space under the drain hole available, and they would have only had to lower the drain hole about 1/3 of an inch to make it simple like every other drain plug hole I've ever seen, without the need for the cut-outs. And I am pretty sure that they are cut-outs to allow the oil to flow out, because otherwise 1/3" of oil and crud would remain in the oil pan during oil changes, and these cut-outs are about 1/8" wide which would seem excessive if their only purpose was to clean the threads of the plug or whatever.
 

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