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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 03-31-2016, 02:44 PM
_330i _330i is offline
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01' 330i Coolant Expansion Tank/Radiator Issue

My coolant expansion tank recently cracked and would not hold coolant. I purchased a new tank and installed it. A couple weeks later the coolant light came on and I developed another leak which was due to a cracked radiator. I just recently bought a new one and replaced it as well. I drove the car about 50 miles and I'll be damned if the coolant light didn't come on again. I limped the car home and am now seeming to experience another leak from somewhere and I have no clue where it's coming from or what to do. All the hoses are dry and of course the radiator and tank are both brand new. The only thing I can think of is the coolant sensor at the bottom of the expanaion tank is missing an o ring of some sort. Does this sensor even have an o ring? Any help would be much appreciated!
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  #2  
Old 03-31-2016, 03:03 PM
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Usually when we replace any cooling part on the E46 we do the entire cooling system as a precaution / preventative maintenance. You SHOULD of replaced the radiator, expansion tank, upper and lower radiator hose, thermostat, water pump and sensors all at the same time.

Now since you didn't every little piece you didn't replace is failing around the new ones. Do you see an actual leak? do you see coolant on the floor? And do you have an automatic or manual?
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Old 03-31-2016, 03:11 PM
_330i _330i is offline
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I don't see an actual leak but yes coolant is on the ground underneath it. And it's a manual. I filled the system and bled it properly. After this issue occurred the tank was completely dry.
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Old 03-31-2016, 03:21 PM
allikanbe allikanbe is offline
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Originally Posted by _330i View Post
I don't see an actual leak but yes coolant is on the ground underneath it. And it's a manual. I filled the system and bled it properly. After this issue occurred the tank was completely dry.
There are two o-rings at the bottom of the exp tank. One is 3.5mm x 22mm Buna-N70 metric. The other is 4mm x 38mm Buna-N 70 Metric. That expansion tank can feel like it's in place correctly, but it may not be tight. It would be worth it to rent a radiator pressure tester to see where the leak really is. Sometimes you can "rent" it for free at an auto parts store.
Good luck.
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Old 03-31-2016, 03:25 PM
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Since you have a manual this make this 10x easier to narrow down. I would recommend taking the electric fan out. And inspect the thermostat, waterpump and lower radiator hose. And like I said... i would just replace all the parts of the cooling system you haven't replaced yet anyways to be on the safe side. The cooling system on these cars isn't something you really want to play round with considering the head is made of aluminum. And these cars DO NOT like heat.
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Old 03-31-2016, 03:53 PM
_330i _330i is offline
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Originally Posted by allikanbe View Post
There are two o-rings at the bottom of the exp tank. One is 3.5mm x 22mm Buna-N70 metric. The other is 4mm x 38mm Buna-N 70 Metric. That expansion tank can feel like it's in place correctly, but it may not be tight. It would be worth it to rent a radiator pressure tester to see where the leak really is. Sometimes you can "rent" it for free at an auto parts store.
Good luck.
Is there an o ring where the actual coolant expansion tank sensor is on the bottom? There's a little play in it and I can't see plastic on plastic properly sealing coolant in a pressurized system...
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Old 03-31-2016, 03:57 PM
_330i _330i is offline
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Originally Posted by MalibuMafiaV View Post
Since you have a manual this make this 10x easier to narrow down. I would recommend taking the electric fan out. And inspect the thermostat, waterpump and lower radiator hose. And like I said... i would just replace all the parts of the cooling system you haven't replaced yet anyways to be on the safe side. The cooling system on these cars isn't something you really want to play round with considering the head is made of aluminum. And these cars DO NOT like heat.
I can clearly see the lower radiator hose and there are no leaks whatsoever. When the system was completely full of coolant the heater blew very hot which would lead me to believe the thermostat and whaterpump were fine. I'm clearly seeing coolant and just need to figure out where it's coming from.
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Old 03-31-2016, 04:11 PM
allikanbe allikanbe is offline
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Originally Posted by _330i View Post
Is there an o ring where the actual coolant expansion tank sensor is on the bottom? There's a little play in it and I can't see plastic on plastic properly sealing coolant in a pressurized system...
O rings

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  #9  
Old 03-31-2016, 04:21 PM
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Quote:
Originally Posted by _330i View Post
I can clearly see the lower radiator hose and there are no leaks whatsoever. When the system was completely full of coolant the heater blew very hot which would lead me to believe the thermostat and whaterpump were fine. I'm clearly seeing coolant and just need to figure out where it's coming from.
doesn't matter if it was blowing hot or not. You can still have a leak....

it's super rare. But there's a heater core pipe that runs along side of the engine block that does eventually go bad on high mileage cars.
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Old 03-31-2016, 10:43 PM
_330i _330i is offline
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The problem ended up being a hose at the bottom of the expansion tank. It wasn't all the way put on. Those metal clips on the hoses are good but they're either on or off, no in between. It seemed to take a a hell of a lot more pressure than any of the others to secure but its fixed! I appreciate the help y'all.
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  #11  
Old 04-01-2016, 08:08 AM
GoForthFast GoForthFast is offline
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Originally Posted by _330i View Post
It seemed to take a a hell of a lot more pressure than any of the others to secure
This is one sign of a binding O-ring, which increases the odds for a leak down the road. Why I urge the use of silicone O-ring lube whenever you see an O-ring. I use syl-glyde.
http://www.walmart.com/ip/American-G...icant/19866160
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