oil drain bolt woes

[woodypup]

hi guys,
after draining my oil i went to put the drain bolt back in. i tighten and tighten, suddenly it gets loose again. i think the threads on the pan are stripped (the bolt looks fine).

any ideas on what to do? i think i may have to re-thread the hole on the oil pan. has anyone done this before? if so, what size tap is recommended, and what size new bolt is recommended?

thanks

[VIDA]

Well, there are a couple of routes you can take. The same thing happened to my 86 325es, but the drain hole threads were flattened out, and the drain plug was shot (the threads had broken).

I was at work when I was performing the oil change, and luckily we have a nice garage, but not much in the way of metric. So I improvised. I can't off the top of my head remember what size tap i used, but it was a standard bolt, 1/2" head, fairly common pitch. It was just barely larger than the drain hole, so I carefully tapped it out and wham! fresh threads. Use the standard bolt, cut it down to size, file and clean. Always use a fresh copper crush washer otherwise you will leak oil like a siv.

The other route, buy a replacement drain plug of the stock size, and a tap of the same size to clean up the internal threads of the drain hole, a fresh crush washer, and you're all set.

Same results, but you choose whether you want it to be a standard or metric.

Hope this helps some.

[coolbear1]

There are self tapping drain plugs available for domestic cars that are slightly oversized and have a integral gasket. They are designed just for this occasion. I haven't been unfortunate enough to need one yet, and I don't know if they have them to fit BMW, but I know they exist for the american made models.

Good wrenching.

[VIDA]

Just a comment on the "self tapping" drain hole bolts. I myself have never used one, but in the business of working with metal, and the permanance of doing anything with your oil pan.

The first time you use this bolt it will probably work like a charm. Each consecutive time you'd probably have to use a new, larger self tapping bolt.

I mean, really, you could use a larger bolt and "force" in in and essentially it will tap itself, but the process of tapping results in the small metal "dust"-like shrapnel. This is not something you want circulating in your oil. Over time, you'd have to keep making your hole larger and larger in order to keep a good seal.

Yes, the American way is a good shortcut that "slices and dices", but in reality the old-fashioned nitty-gritty full turn, back out half, full turn tapping job just does it better. And, it does it permanently. No crossthreads, no 1'' diameter drain hole!

I don't know how long you plan on owning your car, but if it's longer than 2 or 3 oil changes, go with quality over convenience, plus it only takes 10 minutes to do.

[coolbear1]

I personally would get a new/used oil pan they are easy to find and easy to change.Probably easier to change than tap.
Your not going to find that tap a home depot ether.

Get a pan.

Then you dont have to tap anything, and you will feel alot better about it when you are done.

[SGB]

A used oil pan might have a similar problem...
but if you have taken the pan off it can be properly tapped and cleaned up before refitting. Seems like a reasonable thing. You may want to use a helicoil to have a hardened surface....

[Yurick]

Woody,
This is apparently quite a common problem for E30's. I recently went to change the oil in my 325iC and as I was removing the oil drain bolt, the the head of the bolt itself broke off. I tapped out the remains of the bolt, cleaned out the area of metal shavings, and installed a new bolt.
The way I see it, the only way to prevent this from reoccurring is to make sure that the oil drain bolt is never too tight and the best way to control that is to change your own motor oil.