Replace Oil Drain Pan

You don't need to replace the oil pan.

The Prius oil drain plug is M12x1.25.

Those oversize self-tapping drain plugs don't always work.

Your best solution is to tap the hole out to the Honda or Mazda drain plug size, which is M14x1.5.

Get a real tap at M14x1.5 and a M14x1.5 drain plug with gasket, and you'll be fine.

You can also go with M14x1.25 which is used on BMW.

Conveniently, a stripped out 12mm hole is the correct size for using a 14mm tap without the need to drill out the hole.

 

Pick up something like this: Needa Parts/Universal oil drain plug (652006) | Oil Drain Plug | AutoZone.com

It is a rubber plug that expands. It is 1/2 inch, which would be a tight fit, but you should be able to get it in. When you tighten it, it will seal so you can add oil. It should last a while, so you can do a better fix at your leisure.

 

Not to brag, but I am a machinist and technician dealing with aircraft, spacecraft, and mechanical devices for over 50 years.

I have tried and used the rubber plug. It works for a while.

The method I have outlined is the "tried and true" procedure, that makes it equivalent to a factory OEM quality repair. The larger diameter actually makes the repair stronger than the original.

The oil plug screws into a welded nut inside the oil pan. I've seen many of them. It is NOT a case hardened of medium carbon steel nut. It is basically "mild steel." Any standard tap in the correct size will suffice.

If done right, the job is very very easy. The actual job takes no more than 10-15 minutes. And, the results are as good as a new oil pan and a new plug.


A Mazda or Honda oil plug will have the same 14mm hex on the head as the Toyota drain plug.

 

I agree with your repair method, I think it is a good input. If you have the tap and can get the new plug quickly, it is the way to go, but if not, the rubber plug will get him on the road until the job can be done properly!

 

Any NAPA store will have the necessary tap and plug.


Stores like Auto Zone, Advance, O'Reilly, and Kragen carries usually the most profitable fast moving parts.

You can also use "Time Sert's," but they are more expensive and require more work.

Time-Sert Drain Plug Pan Thread Repair Kits and Threaded Inserts

 

Pay $27 for alldatadiy and it will have the torque specs for the pan bolts. IIRC Toyota specified FIPG for the oil pan, but I think Permatex has a similar product.

I would think that the alldatadiy instructions for oil pan R&R would state the cure time require for FIPG. Otherwise Permatex would state on their product packaging, the cure time required.


iPhone ?

 

I think Permatex Ultra Black Max Oil-Resistant RTV may be the correct substitute:

Gasket Makers : Permatex® Ultra Black® Maximum Oil Resistance RTV Silicone Gasket Maker

Says 2 hr for cure time, but overnight for best results.


iPhone ?

 

There is no prescribed pattern to tighten the 9 bolts and 2 nuts. I would gradually tighten the hardware in steps, following criss-cross patterns that you've probably noticed used with other vehicles. The idea is not to warp the new pan.

See below, from the Toyota repair manual.

45. INSTALL OIL PAN SUB-ASSY NO.2
(a) Apply a continuous bead of seal packing (Diameter 2.5 to
3.5 mm (0.0984 to 0.1378 in.)) to the oil pan as illustrated.
Seal packing: Part No. 08826-00080 or equivalent
NOTICE:
Remove any oil from the contact surface.
Install the oil pan within 3 minutes, and tighten the
bolts within 15 minutes after applying seal packing.
Do not expose the seal packing to engine oil within 2
hours of installation.
(b) Install the oil pan No. 2 with the 9 bolts and 2 nuts.
Torque: 9.0 N-m (92 kgf-cm, 80 in.-lbf)
(c) Install a new gasket and oil pan drain plug.
Torque: 38 N-m (387 kgf-cm, 28 ft-lbf)

 

Probably not a permanent fix, but that design looks like a great idea for a temporary measure to get it back on the road. It would probably still work as a temporary solution, even with the distorted sump.

 

Yes

 

The current crop of oil pans are not made of the thick 20 gauge steel found in the pre-1980 car engines.

The are made of thinner high strength steel. The amount of torque needed to use a self-tapping oil plug evidently met with a great deal of resistance. That resistance apparently resulted in the deformation of the sheet metal of the oil pan. Clearly, an experienced technician would not have used a longer wrench and applied more force when met with resistance that deformed the sheet metal.

The technique of installing the new oil pan correctly will depend on your ability and your experience.

The most important thing is cleaning the cast aluminum upper oil sump threaded holes and mating surface.

From my experience, it is absolutely necessary to clean every remaining bit of the old blue RTV silicone off of the mating surface.

Every bit of the RTV must be removed from the screws and tapped holes. If you don't, driving in the screws may crack the aluminum casting. Silicone, like hydraulic oil might be compressed in the hole with tremendous pressure; pressure which nay be released through a resulting crack.

The screws are M6x1.0 pitched. In preparing for such an installation, I would carefully scrape out each hole with a small screwdriver.

Then I would use ether a thread chasing thread restorer or a bottom tap to clean the RTV out on all the threads in the holes.

I would either buy BRAND NEW screws or clean each and every bolt with a die or a thread restoring die. The nuts and studs are NOT as important.

Be advised that you will NOT be able to remove ALL of the RTV residue. That's why torque specs using a torque wrench may NOT be a good idea. The torque specs are for BRAND NEW threads with no silicone residue

The nuts and studs are used to hold the pan in position to aid in installing the bolts. Put them on first, but do not tighten them fully.

When reinstalling the bolts, use a 10mm 1/4 inch drive socket extension with only your fingers to run all the bolts into the holes but do not tighten until ALL of them are in. If you feel any resistance, you need to back he bolt out and try again. Finally, you need to tighten all of the bolts finger tight.

Finally, using a spiral pattern and only short 1/4 inch drive ratchet handle, tighten each bolt no more than 90 degrees or 1/4 turn. Starting from any one bolt, check around the pan with the wrench to make sure that no bolt uas been missed.

 

Lucky you,

From my machinist chart, the readily available standard US 1/2 inch drill bit is the recommended size for M14 threads in both M14x1.25 and M14x1.50 threads. While I have most all drill sizes, most people don't.

To minimize steel chips that might get into the oil pan, I'd grease the tap and withdraw to clean it often.

You probably distorted the sheet metal beyond the small 1/8 inch or less selling area of the washer. So, a new washer will seal.

To catch any steel shavings that fay get into the oil, install a magnetic grain plug.


It is really worth a try.

 

Yep, but it wont immediately go anywhere that's harmful. Just follow this procedure.

1. Drain oil. (Don't change filter!)

2. Either keep drained oil if you have a nice clean drain tub etc, otherwise have on hand the cheapest supermarket motor oil you can buy.

3. Tap drain hole (as per Mikes instructions above).

4. With plug removed, pour some of your used oil through to carry away the swarf.

5. Install drain plug and pour in the rest of the used oil or a quart or two of the new "cheap nasty" oil. Don't run engine yet.

6. Drain the oil again. At least 99.9% of the swarf is now gone. The 0.1% remaining will go directly into the oil filter (and not through the engine) when next you drive.

7. Fill with cheap new oil. Leave old filter in place.

8. Give it a moderate drive to get the oil up to temperature.

9. Drain oil and replace filter. Refill with your regular oil choice.

 

While I agree with Uarts method in principle it is the last part that is problematic.
The oil before it gets to the filter goes through the oil pump. This consists of precision rotors rotating in an aluminium casing with precise gaps.
Any metal particles going through this will score the aluminium and damage the pump reducing it's output and pressure. Maybe that is the best that can be done in the situation, but something I would not be happy trying.

John (Britprius)

 

If it were mine, I would change the oil pan and not take a chance with tapping the drain plug, especially since you bent the pan.

The oil pan should not be expensive and the change out is easy.

 

There's plenty of looseness in an oil pump. Believe me, I used to rebuild Mercedes diesels. Wear is based on the clearance between the tow geared rotors and measured with a feeler gauge. The gears don't rub on the housing.

Unless the metal is very very fine, it will not pass through the oil pick up screen. If so, it will be picked up in he oil filter.

I'd run a small magnetic pickup through the oil drain hole.

Finally, as I said before, a magnetic oil drain plug will pick up most all other steel in the area.