M11 oil pan - More stripped threads

Topic: M11 oil pan - More stripped threads (Read 1468 times) previous topic - next topic

M11 oil pan - More stripped threads

May 04, 2021, 09:48:34 pm

I saw the thread from nine years ago.

I started our first oil change for the new-to-us U320 and the oil pan let loose of the drain hole threads. I kinda knew it was coming. We have had a seep from the plug. When I tightened it six months ago, it just felt weird. Today I had to wrench the bolt loose until it was entirely free. It rewarded me with a cute little silver spring!

So...

I have ordered the Cummins 68749, repair threaded thingie. The old thread mentions "drain hole drilled/reamed out to 1-1/4" and NPT tapped." Does this mean a 1-1/4" drill bit and a 1-1/4" NPT tap? I don't see getting a second chance if I use the wrong tool.

Could someone who has done this or studied it please verify? Any other tips or guidance will be met with big thanks.

Re: M11 oil pan - More stripped threads

Reply #1 – May 04, 2021, 10:06:25 pm

Recommend watching for @Pamela & Mike to respond - much expertise in such things.

Insert plus then doing a Femco/NoSpill or Fumoto drain valve to prevent this issue in the future. Mike will have guidance....

Re: M11 oil pan - More stripped threads

Reply #2 – May 04, 2021, 10:06:53 pm

If it is 11/4 tap you need a drill bit that is sized for tapping to 11/4 tap. If it was me I would order a No Spill drain system as see if
a larger size can be purchase and tap to that size. My coach came with that system and it work great.

Re: M11 oil pan - More stripped threads

Reply #3 – May 04, 2021, 11:27:37 pm

I was threading in a No Spill when the threads fell out. Jor gave me one several months ago.

Re: M11 oil pan - More stripped threads

Reply #4 – May 05, 2021, 12:17:48 am

Matt when I did my first oil drain it was all I could muster to get it loose. I cleaned and installed a quick drain oil drain and torqued to recommended specs. Much lower install than removal. It torqued up and I hope to never remove again. Personally real small threads in aluminum/ magnesium blend is poor at best. Sorry to hear your going thru this
Ism oil change

Scott

Re: M11 oil pan - More stripped threads

Reply #5 – May 05, 2021, 06:48:33 am

When I installed the new drain plug repair kit from cummins I took the pan off and went to a machine shop. Glad I did because when the new insert is put in flush with the outside of the pan it is thicker than the aluminum pan thus sticking up to far on the inside to let all the oil drain out properly. The machine shop then milled down the inside lip.. Imo it is better to have the oil drain out faster to remove contaminates and be sure all the oil has drained. Shop only charged me 100.00. Not very hard to pull the pan then you know it's right.

Larry

Re: M11 oil pan - More stripped threads

Reply #6 – May 05, 2021, 06:59:32 am

Quote from: oldmattb – May 04, 2021, 09:48:34 pm

The old thread mentions "drain hole drilled/reamed out to 1-1/4" and NPT tapped." Does this mean a 1-1/4" drill bit and a 1-1/4" NPT tap?

A 1-1/4"" NPT tap requires a drill size 1-1/2" per the Starrett drill chart (some recommend a 1-31/64), now with that being slightly larger than a 1-1/4" drill, the smaller should/might work for tapping that size. BUT I would go a different way as that bushing from Cummins sucks and there ain't no other way to describe it's function. Wyatt's method is a lot more sanitary and he may loan out his drill and tap. Here is a link to his thread rather than me trying to explain the process along with part numbers as he does a great job. Oil pan plug - striped threads.

Mike

Re: M11 oil pan - More stripped threads

Reply #7 – May 05, 2021, 07:17:38 am

Whoa there!!!! Do not drill a 1-31/64 hole in your oil pan. My machinist guide calls for 1-11/64" drill size for a 1-1/4" tap.

https://www.lincolnmachine.com/tap_drill_chart.html

Re: M11 oil pan - More stripped threads

Reply #8 – May 05, 2021, 07:22:09 am

Quote from: Pyolet – May 05, 2021, 07:17:38 am

Whoa there!!!! Do not drill a 1-31/64 hole in your oil pan. My machinist guide calls for 1-11/64" drill size for a 1-1/4" tap.

https://www.lincolnmachine.com/tap_drill_chart.html

That isn't for a 1-1/4" NPT as a 1-11/64 is for 1 1/4-12 NF

Mike

Re: M11 oil pan - More stripped threads

Reply #9 – May 05, 2021, 10:06:43 am

Thanks all!

I gotta remember that pipe is measured on the inside. The idea of drilling 1-1/2 inch and then tapping UP to 1-1/4 inch messes with my mind.

Still working out my strategy - I will report later!

Re: M11 oil pan - More stripped threads

Reply #10 – May 05, 2021, 01:38:02 pm

When I don't have a chart I take the tap to and index and from that I figger what size drill I need.

Re: M11 oil pan - More stripped threads

Reply #11 – May 05, 2021, 01:58:50 pm

drillchart

Re: M11 oil pan - More stripped threads

Reply #12 – May 05, 2021, 02:31:14 pm

When you tap the npt you don't necessarily use all the threads on the tap because of the taper, it depends on the fitting going into the hole, which can vary in the diameter. By adjusting the npt threading size you can effect how much the fitting will protrude above the inside bottom of the oil pan or even mill or cut the fitting down prior to install.

Re: M11 oil pan - More stripped threads

Reply #13 – May 05, 2021, 09:08:55 pm

Most taps have the drill size to use on the tap.

Re: M11 oil pan - More stripped threads

Reply #14 – May 06, 2021, 09:47:14 am

Thanks for the guidance on choosing a drill bit. I have been waiting out some vaccination aide effects, and have not been lucid-enough for a decent reply.

I have drilled and tapped stuff before - I think dealing with the soft aluminum scares me some. It is good that the oil pan is a replaceable part, in case things go wrong.

Re: M11 oil pan - More stripped threads

Reply #15 – May 06, 2021, 09:51:48 am

Put plenty of grease on the drill and tap to keep metal particles out of the oil pan.

Re: M11 oil pan - More stripped threads

Reply #16 – May 06, 2021, 09:52:49 am

If i had to remove the pan because of stripped threads, I would have the original hole welded up and tap a hole on the side near the bottom as other engines have. Then no issue of getting knocked off with a valve installed.

Re: M11 oil pan - More stripped threads

Reply #17 – May 06, 2021, 09:58:37 am

For what it is worth--per Holo-krome's slide chart, a 1-1/4 NPTF pressure plug nominal outside diameter is 1.660 diameter and the plug length is .812" for 3/4" taper (NPTF) plugs

Re: M11 oil pan - More stripped threads

Reply #18 – May 06, 2021, 09:59:02 am

Quote from: wolfe10 – May 06, 2021, 09:51:48 am

Put plenty of grease on the drill and tap to keep metal particles out of the oil pan.

My tentative plan is to do that, to dump a gallon of oil through the pan after I drill and tap (maybe through the additional side plug,) and to use my inspection camera to LOOK around inside before I seal it up. A 1.5 inch hole is big enough to get a finger or other tool in there to slide any debris out.

I could remove the pan, but that seems like dirt and grit city! Maybe more appropriate for a clean, indoor shop, particularly one with a lift or grease pit!

Re: M11 oil pan - More stripped threads

Reply #19 – May 06, 2021, 10:10:30 am

Had an old man (old to me, at the time I was 27) who rigged up an air hose to his breather tube, blocked his dip stick tube, and then turned on the air while tapping his oil pan. Blew the chips out as they occurred.
Guess it worked as I saw the car running around for a few years after the fix.

Re: M11 oil pan - More stripped threads

Reply #20 – May 06, 2021, 10:11:13 am

Quote from: oldmattb – May 06, 2021, 09:59:02 am

My tentative plan is to do that, to dump a gallon of oil through the pan after I drill and tap (maybe through the additional side plug,) and to use my inspection camera to LOOK around inside before I seal it up. A 1.5 inch hole is big enough to get a finger or other tool in there to slide any debris out. YUP.

Re: M11 oil pan - More stripped threads

Reply #21 – May 06, 2021, 10:25:39 am

I had a provisional patent for a tap with a vacuum port. Designed for medical screws and Ford spark plugs . For spark plugs, turning the engine until the offending cylinder exhaust valve is open. Apply shop air into the exhaust pipe as you tap the plug hole. Blows the slag back at you.
For this instance, you could easily blow air into the breather as you tap . Followed by a quart of ATF flushed with the same air.

Grease on the tap collects most of the slag.

Re: M11 oil pan - More stripped threads

Reply #22 – May 06, 2021, 10:26:11 am

Quote from: nitehawk – May 06, 2021, 10:10:30 am

Had an old man (old to me, at the time I was 27) who rigged up an air hose to his breather tube, blocked his dip stick tube, and then turned on the air while tapping his oil pan. Blew the chips out as they occurred.
Guess it worked as I saw the car running around for a few years after the fix.

Interesting! I considered using a shop vac at the drain hole to draw out any chips after drilling and tapping, but I don't know if the engine fumes would be flammable when compressed and forced through a sparking fan.

Side story. We bought a houseboat from a guy who had gotten it back to life after it sat for years. He told us about siphoning off the old gas, and using a shop vac through an inspection port on the tank to get out the last few gallons and all of the debris that had accumulated over the years. He carried the shop vac up the hill to dump it in the woods. He nearly collapsed when it hit him what he had just done. Saved by the gas being too old to combust!

Re: M11 oil pan - More stripped threads

Reply #23 – May 06, 2021, 04:24:41 pm

Shop vac or any vac sucking on the oil fill will allow the installation of a quick drain, tapping or anything without spilling a drop. Then drain the oil oil and out come the chips. Aluminum chips won't work with a magnet.

I installed my quick drain in about a minute with small vacuum sucking but didn't have to tap.

The drill size is usually on the side of the tap. I like to cut a few threads, back it out and then repeat a few times. Makes cleaner threads and leaves fewer chips inside.

Pierce

Re: M11 oil pan - More stripped threads

Reply #24 – May 14, 2021, 09:15:16 pm

HELP!

Anyone out there have additional information? I don't know enough to put all of this together.

I have the 1 1/4" NPT tap, a 1 1/2" drill bit and the Cummins insert. Good thing I measured before I started. The Cummins 60879 will fit through a 1 /2" hole with room to spare, so something here is way wrong.

The inside diameter of the insert looks to be 1.05 inch, which I am guessing corresponds with the 1" NPT chase the manual recommends to clean and correct (unstripped) threads in the pan. The outside diameter of the insert looks to be about 1.27 inch on the small end and 1.31 inch on the large end.

The outside diameter of the insert is around 1.27-1.31. Is this actually a ONE INCH NPT?

What drill and tap should I be using?

And/or...

In Wyatt's fine post, he says this:

"I taped the drain hole to 26mm by 1.5 which is 1.0236 inch by 17 tpi. This had little more threads than the original 1 inch by 18 tpi hole. I then ordered a 1 1/8 inch tap and Fumoto valve. I tapped the drain hole to 1 1/8 by 12tpi and obtained perfect threads, so installed the 1 1/8 Fumoto valve. Now the aluminum threads are good for life because there is no need to ever remove the Fumoto valve."

Is this to mean that he (you) didn't drill the existing stripped hole at all, but used a 26mm x 1.5 tap, and then used a 1 1/8 x12 tap?

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