Another overheating thread....my apologies.
 

1997 528I 218k
Owned it for 6months
Replaced headers,ccv, alternator, rims& tires, belts and hoses, upgraded stereo system.

A few weeks ago, while sitting at an idle for between 5-10 minutes I noticed my temp had creeped up past the 3/4 line so I turned off the engine. Waited about 15 minutes then drove it home about 5 miles with the temp staying normal tge whole time. It never did it again till tonight. I've sat at idle between the first time it did it an tonight for extended periods plenty of times with no problem. It seems to be random...nothing I can think of thats a common. Maybe the thermostat hanging up ??? Any ideas of where to start looking ? Thanks !

Start with the basics, perhaps excess air has entered the system. If so you can try bleeding the system which is easy. Bleed when vehicle is cold. http://www.bimmerfest.com/forums/sho...d.php?t=558386

Check for leaks, it would be advisable to raise the front end and get underneath and find out if you see anything. Check for fan clutch failure, search the site for fan clutch diagnostics.

It's not random. There's something failing. Bleed the system as per the post above and check the usual suspects.

Perhaps "random" was a poor choice of words....there is obviously something causing it, my bet is on the fan clutch. What I meant by random is that it happens at random times under random conditions. It doesn't happen "every time" I sit at an idle...it doesn't happen "only" on hot days or after a long day of driving or early on first start of the day. Its random as it pertains to the times and conditions. Hopefully I cleared that up without sou.dung sarcastic because it absolutely wasn't meant sarcastically. I know the importance if clarity here and apologize for any confusion. Thanks again to everyone who takea the time.

a better word would have been "intermittent" I would also suspect fan clutch or thermostat

Yes ....intermittent...thanks.