Another Dealer Service nightmare - stripped oil pan threads

yeah, new drain plug seems logical, though the threads on old ones are not severe enough to account for metal chunks... If you were working a job like this full time as a legit mechanic (not at a stealership) you'd open your tap and die drawer and see how existing thread cut responds and if need be upgrade to larger thread size knowing you got another drawer next to you with 20 different sizes of oil drain plug threads and you'd be done with all of it in less than 5 minutes and you'd move on to the next car.

Of course if you're DIYing a problem like this... It takes a little bit longer than that.

 

PS: I used to do the new washer with every oil change routine and it never leaked... Then as time went by I just re-used the same washer and it still didn't link. Then somewhere along the line I couldn't find the washer and did it without any washer and it still didn't leak. The funniest part is that it's been so many years since then I totally forget about the washer until you just now mentioned it. I wonder if anyone on here can prove you need to have a new washer on your oil drain plug because I've can't even prove that you even need a washer in the first place.

 

I cannot add much input other than stealerships suck.
I highly doubt they will take any credit for anything.

I used to get my oil change once a year (low miles) at the stealer, every time I I had state insp.
Until I was changing my trans fluid and noticed the oil change flap was hacked off. (very, very common)
I spent time calling many times to the stealer and talking with service tech manager and leaving
messages to the gen manager.
They never owned up to it even tho I purchased the car from them, and no one ever touched my car except them. ever.

Well needless to say they do not get to do oil changes any more.
I do my own since then. They get to insp once a year and get turned down for any service. (thanks, no thanks)
I keep them in the loop just in case I need them for warranty service.
But I do have many others to choose from if needed.

My advice is to move on, more than likely a waste of time.
Leave them an honest review online.

 

The drain gasket looks reasonable given it went 10k mi since the last oil change. Dealer overtightened drain plug. I use a torque wrench on both once in a blue moon the filter cap is overly tight. If the filter cap was damaged before you unscrewed it then they owe you one of those also, in summary:

Drain plug, oil pan, and oil filter cap.

I would not take it to a different dealer because they aren't the ones that owe you, but I may just buy the three items, under tray, and clips and just replace everything on my own, then as much as possible never get service there anymore.


REVVL V+ 5G ?

 

Stories like this are the reason everything on cars should be requiring a torque wrench

 

I do my own service on my 2015 Prius. I don't use a crush washer at all....and I don't own a torque wrench. Never had a leak. Also the filter is always tougher to get off than you would expect, maybe the heat expands things a bit, but it's not a problem, just tougher to turn than how tight I install it.

 

I can tell you with 100% certainty that the dealer or Toyota is not going to take responsibility for this. Sorry to hear the mishap, but that's what the reality is. You can try complaining, and if you are persistent enough, they may give you a discount on an already bloated repair bill.

As for the stripped thread on the oil pan, it is fairly common on all makes of cars. I actually managed to strip the thread on the Honda using a torque wrench to tighten the drain plug. Yep, I did it, not the dealer. And I did it with a torque wrench properly set at the specified torque. The reason was, I was still very new to doing the DIY oil change, and using a torque wrench was unfamiliar to me. Not sure if it was because of a newly purchased cheap torque wrench from HF which was defective or it was due to a complete operator error on my part. I never felt or heard the "click". This resulted in overtightening the drain plug and stripping the thread off from ~1/2 of the oil pan drain plug hole at the external side.

You can see the sliver of the stripped thread that is still attached to the drain plug (right on the photo). The proper way to fix this would be to replace the oil pan, or at the least tap a new larger drain hole and fit it with a larger diameter drain plug. There are tools for that. But either would be costly. So, I just went with a longer drain plug of the same diameter (left on the photo below). Fortunately, Honda uses a cast-aluminum oil pan and it is thick enough so that there was still about half of the thread left on the oil pan's drain hole deeper section, so this method has worked. I have changed the oil several times since this fix and no leak has occurred, saving a quite bit of money on an older car repair.

I have read in another thread in PC that Toyota uses very thin metal (aluminum?) for the oil pan with a welded nut inside of the pan for the drain plug. Thus it is very unlikely that you have enough thread left inside of the oil pan to "catch" with a longer but the same diameter drain plug. Also, this makes it very difficult to tap a new larger hole onto the existing oil pan. There just isn't enough material to tap a new thread inside of the oil pan surrounding the drain hole. Your only option is to replace the entire oil pan (and drain plug) as you have indicated.

 

Is this true? I had always thought that the plug is made of harder materials than the pan. The reason I ask is because the oil pan is stripped on my friend's Lexus and she is considering to re-thread the oil pan by using a larger diameter plug.

 

I think for the Prius, the hardness is similar because the thread on the oil pan is welded nut on the thin metal. I don't know the physics of the screw thread and how the force is transferred, but in most cases, the stripping occurs on the oil pan thread, not on the drain plug. See my previous comment on what happened on the Hounda. Also for your friend's case, I don't know for sure if the Lexus uses a different type of oil pan as used in the Prius, but if it is similar, then tapping the oil pan may not work. (Again read my previous comment.)

 

It's steel, but yes, it is thin sheet stamped, with a welded reinforcement just for the threads.



The good news is the pan is small and not awfully expensive and not awfully hard to replace, and with a new pan and new plug, you should never have such a problem again, as long as it is only you doing oil changes.

Always make sure you have started the plug straight and true before putting any wrench on it. You should be able to easily twirl it down with your fingers all the way to where the gasket touches. Then use the torque wrench.

From what I've seen, damaged threads happen at least as often from just starting a fastener cross-threaded as from overtorquing. If it doesn't start and twirl in easily and you just say "no problem, I've got this wrench here", then poof! your threads are wrecked.

(When replacing the pan, observe all those cautions very carefully for all the bolts that hold the pan on! Those have quite low specified torques, and they go into soft aluminum threads of the engine block, which you can mess up by looking at them crooked.)

As bettergolf said, the oil filter cap is always harder to loosen. I tighten mine to exactly 18 ft lb by the click every time, and every time it takes more than that to loosen. It's the resistance of the rubber O ring, which I think swells over time while it sits there.

By the same token, I bought my 2010 used, and the first time I had to get that filter cap off, it was a lot harder than that. I barely succeeded. So yeah, sometimes it does get overtorqued, too.

 

Toyota readily gives proper torque settings to everything in their service literature. It is one reason I suspect their vehicles are so reliable. If it shows sign of damage, it's obvious who's at fault....

REVVL V+ 5G ?

 

Thanks. We tried to tap the oil pan sometime ago, but had a hard time. We thought it was probably because the space was too small under the car (on jack stands) and we could not apply enough force. We were planning to do it again. But now with what you said, it makes sense. We may just need to replace the oil pan.

 

Thanks for the clarification and the photo. Yep, there is no way to tap that thread.

As @ChapmanF kindly shared with us in his comment, the photo of the inside of the oil pan of a Prius clearly shows that there is not enough material to tap a new thread. Yeah, your best bet is to replace the entire oil pan and gasket. But, that is definitely a job beyond my DIY capability, best left for a professional. Good luck with yours.

 

I don't think it has a manufactured gasket, but is sealed with "form-in-place gasket" (FIPG, a tube of goop).

I don't think it's necessarily a bad beginner/intermediate DIY project really. The pan's a simple cover held on by 10 little bolts. Once the bolts are out, it will take some prying to separate the old goop. Don't pry in a way that will mar the bottom of the engine block.

You have to carefully scrape all the old cured goop off the block. A plastic scraper is less likely to gouge up the block. The new replacement oil pan will, of course, be clean already.

You need to carefully dry and clean up the bottom edges of the block with some alcohol so they are not oily for your new goop (make sure oil isn't trickling down onto the clean edges from inside the engine). There will be specific instructions for applying the goop, and how much time you have to do it, and how much time you have for putting the pan on and securing the bolts, and how much time from then until you can put oil in.

Follow all those instructions carefully, don't cross-thread or overtighten the 10 bolts, and there you go.

About the only two things that can go wrong are: (1) you don't do the gooping perfectly, and wind up with a bit of oil leak, or (2) you mess up threads for one or more of the bolts.

(2) would be the bigger headache. (1) just means you get another chance to practice. (But you'd be reusing the pan then, so you have to scrape the old goop off both parts.)

 

The biggest obstacle for me to DIY any repair/service on a car is the lack of a safe garage and a lift. I don't particularly enjoy crawling under a car with standard jack stands on my uneven driveway. And with my aging eyes, I can't see very well unless it is very well lit and I can position my eyes perfectly distanced from the object I am trying to focus on. Tire change (already on the rims), oil/filter, and maybe transmission fluid change are just about all I will try DIY on the underside of a car. I don't mind so much working on the body parts, electrical components, or parts in the upper engine compartment, such as the battery, fuse, air filters.

 

Great instruction. Thanks!

 

Dealership has NEVER done an oil change on our 2010. I'm following the 3rd gen Canadian schedule, changing the oil every 6 months (months govern), and have done about 24 oil changes I guess. Never had any problems with the drain bolt, always torqued to spec, and replaced washer.

The plastic shield under the engine bay has been off for every oil change (but the first), and probably 10 or more times. I finally found a few fasteners with missing teeth, ordered some spares (the correct ones) through Amayama.

Some info that might be helpful attached.

 

I wonder if the manual indicates that particular thread'pitch as being torqed wet or dry .... use a dry torque setting with oil all over a plug? forget about it you're stripped