Oil drain plug

The 03 uses a 14 mm ID crush ring. The spec is the same: Use no more than 30 ft-lbs.

If you are uring a new crush ring you will feel the crunch as it sets. I stop at that point and I've never had it leak.

I've had the '90 since it was new. Just for the hell of it, I used the original washer over and over again. I think it finally replaced it after about 10 years. It never leaked. I'm on the second one now.

There is no real reason not to use a new one. If none is handy, however, the world will still turn just fine.

Ken

M. Cantera wrote:

There are a few instances of using no washer with no leaks.

I can't give you a professional answer to your question, but I believe you should be safe be torqueing at 20 pounds. If this results in some oil seapage, you can always go back and tighten it a little more. You probably already know this, but traditionally car manufacturers have made the drain plugs out of softer metal than the threads inside the oil plug hole, in order to to safeguard against over tightening. Theoretically the threads on the plug will strip out before the threads in the hole, resulting in your having to replace the plug, but not having to re-tap the hole. I would like you to first get some second opinions on this though.

Ron, from what I have seen, most modern cars use an aluminum oil pan and a steel bolt, so the threads are going to be softer than the steel bolt unless a steel thread insert is set into the oil pan, which I have not seen yet.

The miata oil pan does not have any such insert, you are screwing a steel bolt into aluminum threads in much the same manner as a spark plug into the aluminum receiving threads, which of course have been stripped out by thousands of people.

Too much torque and that bolt will either strip the threads or crack the oil pan. I had a quick-lube shop do that to a '90 T-Bird SC many years ago.

I have usually just taken the bolt down until tight, then a tiny bit more with a standard short 3/8" ratchet drive. It doesn't need to be that tight and can always be tightened further in the unlikely event that it starts seeping. You obviously don't want it coming loose, but over many oil changes I have found that most people tighten both the drain bolt and the filter far more than is necessary.

It really takes a decent amount of force to damage the pan, but those people at Jiffy Lube can accomplish it.

Pat

As I can't get a socket onto mine, I do it as tight as I can with a ring wrench. Given that I will generally be lying on the ground and doing this at arm's length, I doubt I put more than 20 ft-lb on it. No problems in about 5 changes.

To those of you who enlightened me on the oil pan threads being alumnium, I thank you. I though they were still made the old way. I guess my age is showing. Ron

Try one of these and you'll never worry about it -

On my '96 the guy opened the oil container with a flourish that sent a tongue of oil across my engine, fenders, and even the underside of the hood. So he restrained himself as he poured the subsequent quarts in... all without his pal having replaced the drain plug.

Second time around (after they put the plug in) he didn't splash any more oil around, but broke off my dipstick doing the final check.

If you go to these places, WATCH THEM!

miker

As a cynic, I would have assumed that this is the way it has been done since aluminum oil pans were introduced. Why would a stealership want to sell you a $5.00 to $10.00 bolt when they can instead charge you an arm and a leg for an oil pan and probably for the labor involved in replacing it? The estimate to replace the broken oil pan on the '90 T-Bird was over $800.00 in parts and labor, and this was about 10 years ago.

Pat

Be careful there miker. I once implied that someone who barely makes a living wage is probably not the best person to be wrenching on your car because they are less likely to care than a relatively well-paid mechanic. I was then told that I did not understand people by someone who earns enough to go buy a 2006 MX-5 without giving up their old miata. ;-)

Pat

With one of these drain valves you'd never have to worry about it -

Just about hitting something on the road. That is quite a torque arm.

Does that thing protrude below the bottom of the oil pan? If so, wouldn't it be prone to getting knocked off? Also, is there a way to orient the handle, so it too isn't vulnerable to getting hit? When you have so little ground clearance to begin with, it seems like you would have to be careful.

thx,

Geary

That's the self changing feature, when your oil is dirty you just hit a rock and then all that's left to do is to change the filter, repair the gaping hole in the oil pan and refill it. It's a GREAT time saver!

I can't measure but it seems to me to protrude at most a couple of millimetres and that's the spout rather than the handle, which is more out of the way. I've had mine for several years with no problem but also have very few occaisons to drive on other than paved roads. I think you'd have to be very unlucky to hit anything.

All I know is that I've had to run over at least 2 big tire chunks in the last couple months alone. Both were on paved roads and in traffic where, there was not time or space to avoid the debris. Both were run over by the car in front of me and somewhat flipped up. Not good! Ended up sounding worse than they were however, I did have to remove my mesh guard down in the nose of the car and flatten it out on one of the occasions. Could be some added risk having that thing under there but I agree, you'd have to be pretty unlucky for the exact wrong impact to occur.

Chris

The thing itself sticks out at least half an inch below the oil pan. It has head and valve in series. It will very likely hit whatever is on the road, including the road itself where uneven enough.

I bought one, but never installed it. I would not have trusted it even if the oil pan was steel. Come to think of it, I forgot what I did do with the thing. Probably just threw it away. Can't in good conscience sell it or give it away.

Leon