Lower oil pan nut/bolt stripped

I went through this madness on a Prius C a couple months back... Most people don't know that the oil pan for these engines is universal to most Toyota engines and only cost $30. So I mistakenly thought that would be less hassle than other options.

The Prius I worked on didn't have corroded bolts because it only had 40K miles on west coast but once I got the bolts off the gasket seal held the pan on so tight that I knew it was going to be a huge hassle to get the pan off because the car wasn't high enough off the ground to get lots of leverage with bigger tools under there and the person needed their car back right away.

So instead while oil was still slowly pouring out of the drain plug I pulled out my tap and die kit and gently rethreaded it with same size threads and the oil pouring out at the same time hopefully prevented oil shavings from getting into the engine. If that hadn't of worked I'd of gone one size larger thread and bought a larger oil plug but that wasn't necessary. It worked and was so relieved to avoid dealing with how tight that gasket was sealed on the oil pan.

So that's what I suggest you do. Having one slightly stripped bolt holding on an oil pan that's still on as tight as it was after rolling off the assembly line will be fine as far as I'm concerned.

 

PriuSCamper's response isn't going to help the OP much. The OP's car is leaking "around the lower oil pan", which sounds like a gasket problem, not something that "leave it alone" will fix. Well, unless it isn't really leaking there and the oil is actually dribbling down from further up. Some dye and a UV light would determine which was the case.

I have no experience with working on this part. Somebody who has should chime in. In the meantime...

So, a nut that spins freely and does not come off. Stripped threads on shaft, stripped threads on nut, or stud snapped off and is retained in some way with the retained shaft/bolt turning together. If it is one of the first two the shaft in the middle will not turn with the nut, and if it is the last one it will. For the former case I would break and remove the nut (carefully). With luck it is just the nut which is bad and it can be replaced. If it is the shaft it might be possible to rethread it. Or it might not really be necessary to do so. What is the purpose of that shaft? If it is just alignment having the shaft alone poking through the oil pan might be sufficient.

 

Ouch- sounds like the threads on the stud are ripped off by the nut. So the nut can't go loose or tight. And you don't have enough stud to grab and spin it out.

Option 1: put all the other fasteners back in and let it alone.

Option 2: cut the nut in half with a dremel wheel, then try to spin out what's left after the pan is off. Maybe you will have to cut it flush and drill - tap - helicoil the remains.

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Probably E5 or E6 star socket fits the end of the stud. Wire brush end of stud, make sure socket fits or you will strip it, looks to be corroded similar to the other one on your pan. Harbor Freight has a star socket set for $9.99, smallest is E6, $19.99 has smaller E4, E5 sockets. Or get a loaner set from Advance.

Stud under $2 from Toyota

90126A0004 - Stud, hexalobular. Engine, cooler, oil - Genuine Toyota Part

Turn it by hand, do not use an impact driver.

 

Yes, do not over complicate this. The stud should be able to be removed. The end of the stud will be shaped for a tool, whether it be a T type or hex type. Use the correct tool and unthread the stud. Replace it with a stud or bolt. Most studs are used during assembly as alignment guides, so replacing with a similar size bolt shouldn't be a problem.

 

Sometimes threaded rod like that is welded in place. In those instances there is no shape to the tip to aid in removal. This one does look like it should screw out using a female star driver.

The worst case is when a stud is actually a bolt like piece of metal with the "head" end spot welded in place on the far side of a piece of sheet metal. Use a little too much torque on the nut and the spot welds break and then it is a big PITA since then the stud will spin but cannot be pulled out because it is retained by the remaining "head" part. I recall somebody on this forum having a problem like that somewhere under the dash.

Hmm, anybody know if the vertical stud which holds the three way valve is welded? Mine snapped a few millimeters above that component while trying to take off its (seized) nut. It left enough of a peg that it still immobilized the top of that valve once the horizontal fastener was tightened. I recall that there was a hole immediately below it in the steel member it emerges from, but I could not see well enough into that hole to determine what the situation was.