Replacing Tstat, replace whole housing, or just the Tstat?

so I'm going to replace the thermostat in my 2006 325i. So for i've seen what looked like two different parts, but now i'm pretty sure one part is the full housing assembly, and the other is just the thermostat and half the housing. Here is what i'm looking at:

Full assembly:
http://www.autozone.com/autozone/par...mString=search

Just Tstat:
http://www.******************.com/de...EC1430825.html

Would it be better to replace the full housing assembly or just the Tstat? it's a lot cheaper for the second option, but thought i would get a second opionion.

Also, from what i can tell, i seems like that Tstat is on the bottom of the car, which i thought was strange as every other car i've had it's been at the top side of the car. That sound right that it's on the bottom? Thanks for the help!

I'm not sure what the price difference is, but if you have it done at the dealer/indy shop, I'd get a quote for both and then factor in how long you plan to keep the car. The tstat itself is very cheap but the housing eventually will give out and cause a leak. If you have significant miles on the car and think you will continue driving it for many more years, replacing both while they are in there will give you peace of mind that you should be good in that area for another 60-100k miles.

If you do the job yourself anyway, I'd just replace the tstat and wait for the housing to give out and do that replacement yourself as well.

The car has 82K miles on it, and i plan on driving it for a while. I probably will go ahead and get the full assembly, and i might even try to get it at the dealer rather than autozone, since the dealer is the same price as Autozone, and the dealers part would for sure fit i would think.

Since the Tstat is on the bottom of the car, that's probably going to drain all my coolant out, isn't it?

I'm not familiar where it is located, as I did not have to touch it yet.

For pricing, you may also want to look at www.getbmwparts.com or www.realoem.com.

If you do buy from the dealer parts counter and you are a BMWCCA member, ask them to honor the 10% discount you are supposed to get.

Tischer BMW shows the T-stat for $90. Your Autozone link showed the part for $176?

Thermostat and waterpump are attached, here is a link to see what's involved:
http://www.e90post.com/forums/showth...ight=waterpump

I can still only replace one at a time though right? even though they are attached. I've been looking at a lot of diagrams from the link below and it looks like it's just a short U hose connecting them.

http://bmwfans.info/parts/catalog/E9...N/2006/browse/