hey guys, X5 Overheating, need some help please
 

I've been having this overheating problem after the fan wear out one of the small coolant hose i didn't clamp properly. Some coolant fell out but didn't overheat. Replace that hose (which was the main one from the top of the radiator and the small one attached to it). After driving for a while (15 mins) saw the temp guage was going up. Stop immediately and noticed that big connector at the top of the rad came out. Apparently it wasn't on properly. Now here starts my problem: everytime i would go about 80 mph the temp guage would go up, once I slow down, the guage would go back to normal (halfway). The thermostat and waterpump is new because that was what i replaced when i didn't clamp that small hose. Since then I have replaced the fan clutch and the radiator but the problem still exist. I've tried to bleed it as much as i could according to the bleeding procedure i've read, but still overheating. Now this is a 4.6L and going 80 mph is like cruising with this. I would GREATLY appreciate any ideas or inputs anyone would have to help my problem. Thanks Guys. Note: All parts are geniune including coolant.

Is it possible your sensor is bad? I would remove it and test for ohms resistance. Unfortunitly I do not know what the spec is. Maybe someone with a Bently manual could look it up for you, and post it.

What sensor is this and where is it located?

The sensor that tells your gage how hot it is. Typicly it is threded right into the rad its self. I dont know where it is located, I was just thinking out loud, to try and help think through your problem. The Bently manual is a tell all book. Hopfully someone will chime in soon with some info. I'll google it and see what I come up with.

The ohms of the sensor will be different at all different temperatures, so... can't really test that.

The easiest way to ensure it is bleed properly is to just remove the bleeder screw and pour coolant mix in the radiator cap till it is full to the top and coming out of both holes. Then put the bleeder screw back in and close it off. The excess coolant will just purge out on its own.

Its located on top of the waterpump and thermostat housing. Make sure that your car is completely cool before removing it. RealOEM.com * BMW E53 X5 4.6is Waterpump - Thermostat Look at #9 in the diagram.

I honestly don't think the temp sensor has anything to do with this issue given the details...

The easiest way to ensure it is bleed properly is to just remove the bleeder screw and pour coolant mix in the radiator cap till it is full to the top and coming out of both holes. Then put the bleeder screw back in and close it off. The excess coolant will just purge out on its own.[/QUOTE]

Guys thank your'll so much for your help but I'v done just that. But i'm not sure what radiator cap you're talking about. If its the Expansion tank cap, yes i've done that, pour coolant in there until only coolant comes out of the bleeder hole on the exp tank. I even raised the front of the vehicle at least 18" high.
I dont know what else to check......

And Jordo, thanks man, i saw where the sensor is. (Coolant temp sensor), but i'm not too sure if that would cause it to overheat ( as Weasel said) cause it purges the coolant which means too much pressure or too hot. The cap is new also
I'm really getting fustrated right now.....

Is the AUX fan working? (electric fan in front of condenser)

What's getting me about this is that it seems to be acting opposite of how you would expect... running hotter at higher speeds and cooler at lower. That kinda makes me think waterpump operation, but you say that is new. If all else fails you may need to just bring it in for diagnosis somewhere... better to pay diagnosis fee now than to need engine repairs from overheating it.

Yes the aux fan is cutting in and after a while goes back off.
Yea, everytime I speed up the gauge would go up in less than one min but as soon as I slow down let say to about 40-60 mph it would go back to normal (halfway).
Why would you say it's the waterpump? It brand new but at the same time it could be faulty. But I could see the difference in temp on the top and bottom hoses, well that would be the rad.
I read something about drilling a 3mm hole in the waterpump, do you think thats a good idea?