Help with heater core o-ring part number

[bmwpower]

So I order a heat core kit for my pre 1-90 build 535i and one of the o-rings in the kit is wrong. See the small o-ring? It doesn't exist on this heater core....go figure...people replacing your heater core with one of these kits - beware.:

http://img.eautopartscatalog.com/live/R3000169038BEH.JPG

So I informed BMA, but I wanted to get things back together ASAP so I had to order the right o-ring from the dealer.

One part comes back differently than ordered (wasn't there to pick it up in person so I could not ask them what was up).

I ordered:

64-11-8-377-824 (http://www.realoem.com/bmw/showparts.do?model=HD23&mospid=47408&btnr=64_0174&hg=64&fg=15&hl=20)

I got:

64-11-1-468-436


I cannot find 64-11-1-468-436 anywhere within realoem or bmwfans.info. I did a google search and it seems as though this part might be the valid part since I come up with a bunch of hits for other parts vendors for E34, E30, etc. Not sure why it's not in the system unless it's a really new part or something. I just want to make sure this is the right kind of o-ring and the right size cause I reeeaaaallly don't want to be opening this heater box anytime soon.

[zubbie]

If I understand you correctly, the small O ring should be a bigger size? (from the Realoem picture 18) I'm pretty sure this new part number is a 17.12 mm o-ring which will mach the spec. It's a valid substitution for a number of part numbers. See link at bottom of page http://www.partsquick.com/ProductDetail.asp?i=79293

http://bmwfans.info/original/images/8665_p.png

[bmwpower]

Yep, that was the problem - it was too small. I used the new o-ring last night and things seem to be fine - no leaks, etc. Will wait a couple of days driving before closing everything back up.