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2002 BMW E46 and 1989 BMW E30
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Discussion Starter #1
Hello!

I have a BMW E46 320i 2002 Touring with quite a cooling problem.
One day I was driving and the drivebelt popped off, then expansion tank split at the bottom. I then saw water on the road behind me and i stopped the car at the side of the road and towed it home. At home i replaced the new belt and noticed that the engine was still overheating. I shut it off and checked the thermostat, i also replaced it. We then tried starting the car and still got the same issue. The car was overheating. Also the water in the expansion tank was boiling.

I procceded to check the hoses and i noticed that the hose going into the thermostat was warm and hard. And the lower radiator hose was cold and soft. I think that the water is not coming through the thermostat and thats why the lower hose is like it is.

I also checked the symptoms for a blown head gasket, like white smoke, gew in the oil filler cap and also oil in the expansion tank. But i had neither of them. What are you guy s though about this and how would i go about fixing the problem? Any idéas?

Thanks
 

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Ho long have you owned the E46? Do you know it's history?
what caused the belt to slip off ? Did you also replace your expansion tank?

It sounds like you haven't bled it properly. I would try and bleed it again.
If you replaced thermostat it should be fine. If unsure, put the old one back in.

Learn how to unlock the cluster and read test#7 which shows your coolant temp.

After you do all the above, and it still overheats, please describe the overheat...Does it happen quickly? only at idle? etc.
 

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...or a failed pulley might have seized and burned through the belt...make sure that's not happening...if bleeding and/or wp doesn't work...and not a bad idea to replace therm anyway while system is open...usually therms fail 'open' but not always.

Hope it's just a bleeding issue.

Good luck.
 

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As mentioned, it may be time for a cooling system overhaul. I'd tear it all apart including the water pump, thermostat, ET, pulleys and hoses. I'm sure you learned from the E30 on your profile that the cooling system is the weak point on the 3Series and shouldn't be neglected. Do the overhaul and you should be good for quite awhile. More important, it will give you peace of mind.
 

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2001 E46 330Ci, LSD diff, Dinan performance, Facelifted Mpackage
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Hello!

I have a BMW E46 320i 2002 Touring with quite a cooling problem.
One day I was driving and the drivebelt popped off, then expansion tank split at the bottom. I then saw water on the road behind me and i stopped the car at the side of the road and towed it home. At home i replaced the new belt and noticed that the engine was still overheating. I shut it off and checked the thermostat, i also replaced it. We then tried starting the car and still got the same issue. The car was overheating. Also the water in the expansion tank was boiling.

I procceded to check the hoses and i noticed that the hose going into the thermostat was warm and hard. And the lower radiator hose was cold and soft. I think that the water is not coming through the thermostat and thats why the lower hose is like it is.

I also checked the symptoms for a blown head gasket, like white smoke, gew in the oil filler cap and also oil in the expansion tank. But i had neither of them. What are you guy s though about this and how would i go about fixing the problem? Any idéas?

Thanks
there could be allot of possibilities and not enough explanation on your side.
like you mentioned it sounds like the thermostate isn't opening for hot coolent to go to your radiator hence why the lower rad hose is cold and soft

have you installed everything correctly? wires to the sensors are connected?
hove you bleed the system properly after you changed the thermostate?
 

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2002 BMW E46 and 1989 BMW E30
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14 Posts
Discussion Starter #8
Ho long have you owned the E46? Do you know it's history?
what caused the belt to slip off ? Did you also replace your expansion tank?

It sounds like you haven't bled it properly. I would try and bleed it again.
If you replaced thermostat it should be fine. If unsure, put the old one back in.

Learn how to unlock the cluster and read test#7 which shows your coolant temp.

After you do all the above, and it still overheats, please describe the overheat...Does it happen quickly? only at idle? etc.
I have owned the car for about a year or so. There was alot of bad jobs on the car because of the previous owners. What caused the belt brake is something i don't know. I can try to bleed it again. The overheat isn't to fast. It happens after a while when the car is started. It happens at idle as far as i have tested it. But i suppose it happens faster while the car is driving.
 

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You may also want to consider the fan. I've got a 2001 325ci 5 speed manual. My expansion tank failed and after I replaced it and bled the system the car was still overheating. I noticed that the car would start overheating after a few minutes. The fan would kick on and start spinning. However, the fan wasn't spinning hard/fast enough. After I replaced the fan my overheating issue was resolved.
 

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I wonder if a previous owner used "stop leak" or other similar product.. Stop leak will harden and can cause flow obstructions.. please look for it when you change your water pump, although you may not see it there. I have pulled hardened stop leak out of the pipes leading to/from the heater before.
 
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