Another Dealer Service nightmare - stripped oil pan threads

It would be kind of silly if they specified a no-oil torque for an oil drain plug.

I've routinely been putting their specified torque on my all-oily drain plug and have never come anywhere near stripping it, so I'd have to conclude their engineers aren't that silly.

 

"Clean and install with new gasket". Dry but it will be coated with oil as you insert....

REVVL V+ 5G ?

 

As an engineer wilt some extensive knowledge of screw threads and metal fatigue, 28 ft lbs is nothing but the standard torque fasteners for M12x1.25 threads for bolts holding parts to be fastened together.

A lot of manufacturers are switching to 35% glass filed PA6-6 or nylon 6-6 and using plastic drain plugs where the effective sealing unit is an O-ring, not a crush washer. O-rings, like gaskets, do not required by the nearly a ton of pressure applied to the sealing surface to achieve a leak-proof seal.

The high torque pressure and metal to metal seal is a throwback to the early days of the automobile.

The threads of both the oil pan recess and the drain plug are like linear vanes fastened on one edge. Every time an oil plug is tightened and loosened, these vanes are bent back and forth at the root edge. It's like bending a paper clip back and forth. Eventually, the crystalline bonds in the steel separate. This is called breakage or fracture. The result is called stripping.

Basic physics in Robert Hooke's Law states that "Stress is proportional to strain." Applying a lower torque value of 10 foot pounds to the oil plug would make the threads last many times longer than those tightened at 28 ft. Lbs.

This Ford plastic drain plug limits the torque only a few foot pounds by using a limited camming action to prevent over tightening while physically controlling the compression of the sealing O-ring.

To seal the plug, I have ditched the crush washer and replaced it with a Viton O-ring. I have found the size 112 O-ring to be the ideal size for the Toyota OEM M12x1.25 drain plug. Here's where I got mine.

It is the ideal size and tightening the drain plug to 10 ft lbs will compress the O-ring to the outer edge of the flange of the washer edge of the drain plug. The friction and compression force of the plug will hold it in place like a lock washer.

At 10 ft lbs, the plug will not work loose from vibration and will stay in place just like any other gasketed assembly. The drain plug does not need 28 ft lbs of torque to hold any two components together. It just has to hold itself in place.

The drain plug can be held on securely and sealed by the friction of and compression of the O-ring just like a spin on oil filter.

 

This kit is a good option, of you do not want to change the oil pan.

Best Q M13 x 1.25MM Oil Drain Plug Tap Thread Repair Kit Oil Pan Screws Rethread Tool

I would still, however, switch from crush washers to the low torque required o-ring method to avoid future trouble of stripping out the threads in the oil pan.

 

Do I miss something? I don't see any links or pictures.

 

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Best Q M13 x 1.25MM Oil Drain Plug Tap Thread Repair Kit Oil Pan Screws Rethread Tool

 

TapaTalk does not seem to allow Amazon links as well. Go to web view option in the upper right corner (3 squares).

REVVL V+ 5G ?

 

Thanks.

 

The plug and the threads in the oil pan are actually made of softer "ductile" rather than harder brittle or frangible metal.

The harder the metal is; the more brittle the metal is and more likely to crack rather than stretch and deform. Ductile metals will deform and stretch and hold a structure together.

Repeated high torque tightening to 28 ft lbs and releasing the tension by removing the plug will "work harden" the threads and make the threads more likely to crack. The close to the "yield point' that the fastener is tensioned; the more likely it is to fatigue. Steel tensioned to a small percentage of the yield point will almost never fatigue and fail.

The theory with the Titanic is that the steel was not ductile enough in the cold Arctic Sea and cracked rather than deformed.

 

How far between Portland and Vancouver? Maybe you could borrow Mendel's tree stump.

Once in my reckless youth I left a car up on glass apple cider bottles while going off to buy some parts I needed. (I did not work beneath it that way! It was just so I could put away the jack and tools rather than leave them unattended.) Glass is pretty darned sturdy as long as the loading is even and nothing starts a chip or crack....

 

If the permanent oil filter housing is giving you fits, conversion to spin-on is doable. IIRC there's a link in my signature.

 

Asked and answered.

I wouldn't waste my time going back to the dealership.
For anything.
EVER again.
(I haven't even bought CARS from them in over 30 years )

As mentioned above, you can repair the threads more cheaply than getting a new oil pan and perhaps get a oil drain plug with a gasket.
I do not consider a 10K OCI to be wise maintenance practice, simply because most people simply do not check their oil level every 1k or 1m like it says in the manual, so I would consider a 5kOCI and if you're going to be keeping the car long enough to justify the cost I'd also convert to a normal oil filter.

Some people change the oil every 5k and the filter every 10k.

There's lots of ways to do it, and quite frankly if you have a "dealer serviced" G3 that's 10 years old you have MUCH bigger issues than oil pan threads and housing covers.

Good Luck!

 

Using the Best Q M13 x 1.25MM Oil Drain Plug Tap Thread Repair Kit Oil Pan Screws Rethread Tool appears to be the best first option.

Although the welded nut is thin, half of a milometer is not much more to cut into the wall of the threads.

The threads will be as new, since it will be into the underlying ductile metal beyond the work hardened micro cracks that separated the roots of the original threads.

 

I put my jackstands at the scissor-jack support points ONCE, swore never again; they are way too flimsy/skittish. I use the points marked up in the oil change link in my signature. Also, whenever possible, I have this section of tree trunk, about 12" diameter by 12" long: I pushed that under a strong point, in vicinity of where I'll be crawling under, for insurance.

 

My methods;

 

I've been replacing drain plugs by Fumoto drain valves on all my cars for years.

 

Maybe the advent of ubiquitous electric impacts, coupled with rushed, junior mechanics? DIY hand tools and a torque wrench, I’ve never had a problem.

Hey Toyota: put an oil change instruction, complete with torque values, in the Owner’s Manual.

 

& how does that best serve Toyota service department interests

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