Welcome to the forum, I've moved this post to the X Forum, might get a better response. 

 

http://www.bavarian-board.co.uk/forum_posts.asp?TID=25689&PN=2" rel="nofollow - I replaced the thermostat and water pump in my 523i without having to take the rad out.  You have the http://www.realoem.com/bmw/showparts.do?model=FA52&mospid=47740&btnr=11_2180&hg=11&fg=35" rel="nofollow - M54 engine which isn't a million miles away in terms of how to get in to work on it.

 

I did then thake the rad out after everything else as I could then see that it was only held in with two screws and a pair of clips.  Quite straight forward really.

 

The tricky bit was removing the viscous fan.  I had to remove this to gain access to the thermostat housing.

 

A dodgy thermostat can be identified by a wavering temp gauge, on BMWs the needle should steadily rise to the vertical then not move either way.  A knackered 'stat will show up with the temp gauge not getting to vertical or moving off verticle back to cold.  Or a really poor heater performance.  But bear in mind, if at this time of year you don't get any faster than 40 mph and have your heater set at hot from moving off, you might find that it never gets properly hot as you are not working the engine hard.

 

HTH

 

Andrew