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Discussion Starter #1
Due to a sticking thermostat (sometimes too cold) I bought another online and replaced it. I put in a bit too much coolant, and about 5 miles down the road I'm in the red, so I kill the engine. A random homeless guy offered car advice, and then ripped open the radiator cap! A bunch of coolant poured out, and we let the car cool a bit then carried on. No problems. The temp guage stood at 12 O'clock the rest of the night.

This morning I noticed the coolant light was on after 30 seconds of idle, so I put a little bit in. Keep in mind there was no puddle, drips, or anything on the ground and the thermostat is bone dry along with the rest of the engine bay. My guess is the air had come out of it.

Anyways, I start off to work and the needle goes to the 12 O'clock position and stays there, all is good in the world. But after a bit of driving I notice it rising, then dropping back to 12 O'clock. First to the hash mark at the end of the operating zone, and with later iterations past that mark. It eventually got too close to the red, so I killed the engine and coasted into the parking lot.

I felt the engine, it didn't seem hotter than normal. Do I have too much coolant bothering the engine, or another problem? (I am not jumping to conclusions by saying the thermostat is bad, because it worked fine last night).
 

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You need to bleed the air out AND add coolant.


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Discussion Starter #4 (Edited)
That bolt was replaced by some red sealant by the previous owner... I opened the expansion tank and let a bit of coolant come out there. I'm running the heat at 91 F, but the air coming out isn't hot at all.

So I could peel off this redneck fix, but I'm assuming it's there because the guy stripped the threads. Should I try taking the red stuff off and tapping a new hole?
 

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The system needs the air bleed out so how you do it is up to you. Opening the Expansion tank cap should be okay...
 

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Spend the 20 bucks to replace the upper radiator hose so you can bleed it properly.
 

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2004 330Ci 85k miles
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If the threads of that bleeder port in the upper radiator hose are stripped, then replace the hose. You need that bleeder screw to function properly.

Check that your cooling fans are working properly. You may have just an electric fan (MT) or both mechanical and electric fans (AT).

A few tips for you:
- Read Mango's cooling system guide. http://forum.e46fanatics.com/showthread.php?t=914109
- Only use a 50:50 mix of distilled water and genuine BMW coolant.
- Check the coolant level only when the engine is stone cold, like in the morning.
- Never open the coolant cap on a hot engine. It's dangerous, and the loss of pressure makes the hot coolant boil thus reducing its cooling effectiveness. Always wait for it to cool down before opening it.
- Use the proper E46 coolant bleeding technique. See Mango's guide.
- If ambient air temperature is above 90F, wait until it cools down to bleed as the heater valve won't open.
- If the temperature gauge starts rising shut off the engine immediately. Do not let it get to the far right!
 

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Discussion Starter #8
At what point should my fan come on? And how long will it stay on for? A spotter said he saw the fan turning on and off, and wasn't moving too quickly. If I take the fan out of the car (electric) and sit it on the engine, will I be able to see it spin better?

When I run the engine it goes for about 10 minutes idling with the needle in the 12 O'clock position, then the needle begins to rise and I cut the engine around the upper hash mark of the operating range. The more cycles I do, the less time between start and when I turn it off (it spends less time with the temp needle at the 12 O'clock).
 

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The fan is not your primary concern. Air in the system can block cooling pasages and/or fool the temp sensors.
If the previous owner did that to the bleeder, he may have done other stupid things to the cooling system. It's probably better to take it apart and replace evertything in one go rather than doing one component at a time.
 

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Discussion Starter #10
Alright, I'm going to Bavarian Auto before they close. I'm getting fresh coolant and a new upper radiator hose. Suggestions for anything else I should buy when I'm there?
 

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What's the mileage on your car? I would replace the expansion tank, lower radiator hose, & water pump. Not all that expensive & fairly easy do but as others suggested I would also read Mango's cooling system guide. Be careful not to overfill the expansion tank when adding coolant.
 
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