Corroded Transmission Drain Bolt Problem

It will probably help to get de transaxle nice and hot before draining en before that spray some penetrating fluid on de bolt so it can creep between the threads.
You might try a small electric impactor to loosen it if it feels stuck. But with whatever method you use be gentle.
After that, replace the bolt if it looks to badly corroded.

And perhaps the most important, use a high quality Torx bit which had a snug fit in the head of the bolt. Many cheap torx tools have quite loose tolerances.

 

To be clear: it requires a 10mm HEX socket (NOT a torx bit), and I'd suggest getting it in a 1/2 inch drive, so you can CAREFULLY use it with a 1/2 inch breaker bar (CAREFULLY).

Also: as stated on PC several times, make SURE you can successfully remove the FILL bolt from the transmission BEFORE working on the drain bolt; other wise you'll be in a serious bind...

 

The steel plug is threaded into the cast aluminum housing of the transaxle. The aluminum sealing washer is under the head of the drain plug bolt. This means the thread interface between the steel threads and aluminum threads are bathed in transmission oil. Accordingly, there is little likelihood that the plug threads are corroded or "frozen" through corrosion at the threads' contact surface.

The corrosion appears likely between the head, the washer and the contact surface to the outer surface of the drain port.

I'd recommend cleaning the arear around the washer, the head of the plug and the drain port with a small "toothbrush" sized wire brush. Then, I let it soak with penetrating oil.

I would not use any type of impact tool with the necessary 10mm Allen head hex driver. Instead, I'd get a 10mm "L" type heh wench and a piece of appropriate "cheater" pipe. It is very important to apply direct pressure to the hex wrench with constant direct pressure on the axis of the drain plug. While applying the direct pressure, rotate the "cheater" in the counterclockwise direction.

The plug will have to break loose. When replacing the plug, I'd coat the washer with aluminum based anti-seize lubricant before installing it.

 

Using my method, it will not likely strip. You have to make sure the hex wrench contact the bottom of the hex socket. You can "feel" that it is camming out and reposition it.

 

Confirming as said above, it is a 10mm Allen (hex bit) that is needed. If you don't have a 10mm, but do have a 3/8", the 3/8" may appear to fit fine, but definitely do not use it. It would be likely to strip the hole (turn the hex into more of a circle, making everything else you try more difficult). In many cases it would work, but with the problem you're describing, it would be a risk.

Some things that may help getting things loose without stripping:

- It's good common advice with drain and fill plugs to make sure you can remove the fill plug before you remove the drain plug, just in case you drain it all out and then can't refill. BUT, in this case, the drain plug is more easily accessible. So I'd recommend working on getting that one loose, without removing it, before looking at the fill plug. Just get the drain plug loose, then tighten it so nothing drains out. You will probably learn a few things from doing the drain plug, which will then make the fill plug easier.

- clean out the inside of the plug - i.e., where the hex bit inserts into. Use an awl, screwdriver, etc., to clean any dirt or corrosion out of there. You might think that scraping that crap out of there will mean it's a looser grip, but actually all that stuff would do is to facilitate the bit slipping out of there. So clean it carefully.

- once cleaned out, make sure the bit is well seated inside the plug. This means to tap it in so the bit goes all the way to the bottom of the plug. Again, this is to help prevent it from twisting out of the plug when you apply torque.

- there is a challenge with the proximity of the intermediate shaft coming out of the transaxle there. So when I did the ATF change on my 2012 last weekend, I ended up using about 3 or 6" of extension on the hex bit - in between the bit and my ratchet. I had no problems since the plugs were like new and the tools were solid, but if you've got weak plugs and need everything tight, you'll need to be careful with an extension like that. If pulling hard on the ratchet, with a 3-6" extension, it will provide more torque that is trying to pry the bit out of the plug vs. to loosen the plug. So what you do, as normal in cases like this is to use your other hand to brace the end of the ratchet from moving, so hopefully you get a purer torque on the plug, reducing the chances it will cam out. If you have doubts on this, you may want to spend some time figuring out how to go with shorter (or no) extensions.

- if the hex hole ends up stripping, at that point, you can try to use a slightly bigger Torx bit, tapping it in there. Another option is XZN (triple square) bits, which typically have very sharp points.

All of the above do take some thinking and effort. Made easier if you already have all these tools at your easy disposal. But if you try the easy approach and it fails, further damaging the plug, you may dig yourself deeper into the hole.

 

you're probably fine, but if you can't get yourself to give it a go, let the dealer do the first change

 

yep, then the dealership can be blamed and replace it for free

 

Yeah, Stanley makes a nice set of metric hex-bit "sockets". Use them with a long-handled ratchet wrench or breaker bar, you'll be good.

 

Yeah remember that thread.

Honda has a similar "socket head cap screw" for the transmission drain bolts, and fill is often through a good sized dipstick hole. The one difference: the drain bolt recess is 3/8" square. No specialty tools required, just a 3/8" ratchet wrench.

 

Here is what happens if it does not break easily and you accidentally drain.

With every reference to ensure the fill plug is free before draining, while under the car I forgot and proceeded w/the draining to return later to open the fill plug. WD40 applied to both bolts, and waited until inside of plug was dry to minimize problems.) With the proper 10mm hex socket and 1/2" wrench (however wrench itself does not have the angled head) ensured there was a snug fit. The drain value took a great deal of pressure to free....and required a pipe assist. Did the same w/the fill plug and stripped the socket where the hex now looks like circle. Tried vice grips and different tools w/o progress.

Prius is sitting on 4 jack stands w/o transmission fluid ~ and our only vehicle.

If anyone else ran into this, how did you get the plug removed? Are there any other, less conventional, means to fill transmission?

 

UPDATE: Tip from Nuts&Bolts which worked: Used a chisel and hammer to create a mark enough for a screw driver to grab...switched to the screw driver and hammer and it spun out like it was brand new!

 

I have found that fasteners and plugs with recessed drives (hex or torx) often go best with the following:

1. Clean the recess, so the tool can seat fully. Compressed air, carb cleaner, dental picks & toothbrushes all help.
2. Tap the tool in with a hammer to make sure it lands in the bottom
3. Give it one extra sharp whack to help break the bond on the threads
4. Use articulated handles or bars to keep the tool on-axis

 

Yeah ... there's one kind of "impact" that works magic in these situations. Not the kind from an impact wrench (which uses impact to create large shock torque that can twist things into pieces or round off heads). Just the kind that bops straight down on the axis of the fastener, and breaks the corrosion bonds between the threads.

PixelRogue's chisel and hammer were doing more than just making a screwdriver slot. That's why it spun out like it was brand new after that.

For what it's worth, Lisle sells a "seized fastener removal kit" that works on the same principle. It's used with an air hammer, just to gently (light touch on that trigger!) and rapidly keep bopping straight down on the fastener, while you just use a normal wrench and hand pressure to turn the tool counterclockwise. Thexton sells a similar tool also.

 

Yep nothing like rust to ruin your day! Some great advise already given and my friends who live in the "rust belt" also have various torches and impact-hammers when the poop hits the fan. With aluminum engines you have to be doubly careful.
The worst transmission drain bolt I've encountered is my daughters 2012 Sienna but patience and penetrating oil did the trick. (And when it lets go, watch out...it lets go completely!) The rusty bolts on her rear brake caliper were, also, a bear to get to break free.

 

^ Similar principles in all of the above. I don't have air, but a few taps on the socket with a heavier ball-peen hammer before attempting to loosen, seems a good idea, both to "shock the threads", and fully seat the socket.

Is the following link similar?

https://www.kmstools.com/wera-koloss-1-2-quot-ratchet-with-built-in-hammer.html

 

That looks like, umm, a ratchet handle, that also caters to people who reach for a nearby ratchet handle and turn it sideways, when the hammer is across the room. Something I have been known to do, now and then.

 

Ah ok. I was thinking you could hammer on it while turning the ratchet.