SoCal 1999 MX-5 (Oil Pan issues)
 

Hey y'all...

New here, my son has a 1999 Miata and although he'll have all sorts of questions about mod's ect right now we have more pressing issues...

Last week he did an oil change, nothing unusual and he's been a lube tech in the past so I'm sure that's all good but the vehicle has developed an insistence on leaking from the drain plug ever since.

It looks like the oil pan has a helicoil from the prior owner(s) and I'm afraid we may be looking at replacing the pan altogether.

I've been searching the forums for any guidance and will continue to do so but in the meantime, any suggestions?

It's is DD so this is highly important to him. thanks!

Questions - how to replace the pan? ever seen a helicoil leak way after the fact? what's the right washer for the drain plug, copper or aluminum? etc.

Any help appreciated!

Thanks!

This is an aluminum pan right?
These guys show how to use a Time Sert to repair a stripped oil plug hole:

Yours has been done already once, so it may be necessary to go oversize if there is enough material.
Also it is possible to weld aluminum. So a good fabricator could weld in a plug and cut a fresh thread. And then there are these junk yards....

Looks easy enough but i hear they are pricey! :(

there doesnt appear to be any wear at all but it does look like it's been done before. ever heard of a drain plug wearing out? ugh, maybe i'll get a new plug and washer, try it all again.

Yes. They can wear out. Aluminum is soft. The plugs are made of steel, usually magnetic steel, and steel is hard. According to Moore's law the harder stuff will wear the softer stuff. But more likely it has been damaged by over tightening. It will re-shape the profile of the threads from 'A'-shape to "A"-shape. As a result a little gap is created between the threads of the plug and hole. Also the contact surface between the threads is reduced and now the plug cannot be tightened enough anymore to keep the washer under sufficient pressure.

But: you may be lucky and a new plug and washer will do the trick.

Well, so far so good... turns out the metal insert was not flush with the pan so the bolt/gasket(washer) wasnt able to make a good seal. ON top of that the insert is just a tad off kilter so there was almost no contact with part of the pan/bolt/gasket.. off just a smidge but enough to cause issues.

The fix so far was a careful dremel tool application to bring the insert flush with the pan, a replacement bolt/gasket and 30Ft/lbs of torque.

We will likely bore out the insert and redo it properly at some point but for now i think this is the ticket. Maybe we do oil extraction instead of draining via the plug from now on. :)

THanks for the link, we'll consider that for sure if we go to replace it.

Don't you love having to fix someone's hack job.