quick temporary solution - alternator cap nut

Russianblue · #1 10-28-2018, 12:40 PM

My car is in the garage with the entire cooling system and Oil filter housing removed. wife is out of town until tomorrow night and I am supposed to be somewhere tonight.

overhaul is going beautifully, BUT...I dropped the alternator cap nut in the nether regions (I ALWAYS drop something down there but usually find it). This time, no dice.

Do any of you know the thread pitch of that nut? I believe the post on the alternator is M10. I might have to uber to Home Depot to find a nut to use until I can order a new cap nut, but wanted to know if anyone knows where on the car there might be another, less essential version of a nut I can scavenge and just use temporarily. doesn't have to be plastic. just needs to be able to hold the battery cable in place so I can drive to get a replacement. also would autozone or a place like that have something generic that would work since these valeo alternators are fairly ubiquitous?

thanks!!

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andrewwynn · #2 10-28-2018, 12:53 PM

The nut is a standard M8. I know this because I only thumb tightened my alternator when I reinstalled it. It of course vibrated loose and though I retrieved it months later from the foam above the stiffening plate I needed it to work.

You won't need to get a replacement before you eventually do some work requiring stiffening plate removal. A normal M8 nut with a washer is a permanent fix. The only thing special about the OE part is the outside is plastic so you won't short out the tool used to install it. Should go without saying be very careful installing the non insulated nut: I put a rubber hose over my wrench.

Russianblue · #3 10-28-2018, 01:04 PM

if i don't have an M8 nut available somewhere i am gonna lose all my BMW street cred!

so standard thread is what, 1.0 thread pitch?

cn90 · #4 10-28-2018, 01:30 PM

- Get a telescopic mirror and flash light and look around, you will find it somewhere on the stiffening plate.

- Or remove the plastic shield below the front bumper, this gives you access to the stiffening plate. Info is in the cooling overhaul DIY I wrote a while back.

https://xoutpost.com/bmw-sav-forums/...16k-miles.html

wpoll · #5 10-28-2018, 04:32 PM

Quote:

Originally Posted by Russianblue

if i don't have an M8 nut available somewhere i am gonna lose all my BMW street cred!

so standard thread is what, 1.0 thread pitch?

Likely to be a M8x1.0 - so yes, 1.0mm pitch.

And maybe pull the battery negative terminal off to avoid some engine bay "welding" while fitting it...

andrewwynn · #6 10-28-2018, 06:20 PM

I bought mine at home Depot. M8 is a rare size.

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oldskewel · #7 10-28-2018, 06:42 PM

It is an M8 nut.
torque spec for that nut is 13 Nm
DIN coarse thread pitch standard for M8 is 1.25 mm. But I do not know whether that particular nut is coarse or one of the two fine options (1.0 and 0.75). I would guess coarse.

Any auto parts or hardware store should have that.

I definitely agree with the advice to make really really sure not to weld anything.

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