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I have a 2003 325i. I have replaced the overflow tank due to it bursting, the water pipe hose, the radiator, the water pump, water pump pully, fan clutch and fan blade. Somehow my system is still getting hot despite my being sure that each new part would solve the problem... what next? thermostat? seems like the only thing I havnt replaced due to it seeming to open and close just fine.:thanks::thanks::thanks::facepalm:
 

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Replacing those components rarely relieves excess pressure in the cooling system. You may have a bad head gasket, which allows exhaust gas to enter the cooling system. You need to do, or have a mechanic do, a compression test to rule in/out a bad head gasket. You can also get a test from autozone that tests coolant for exhaust gasses, but I prefer a compression test. You can borrow a tester from autozone
 

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Did you bleed the system or just fill it and drive? There is a procedure for refilling these systems. Front end raised preferably, engine off but key to the run position. Heater temperature on high, fan speed on low. Bleed screw out, fill the expansion tank slowly until you get a bubble free stream of coolant out of the bleed hole. replace the bleed screw, remove excess coolant from the tank replace the cap and start the car, watch the gauge , as the temp starts to rise check for cabin heat. Bringing the rpms up can help push air out of the system. Once you have good cabin heat and it's not over heating take it for a short drive to make sure it's not running hot, if it's not, park it overnight and check the coolant level once it's cooled down completely. Adjust the level and check everyday till the level stabilizes.
 

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OP, it usually is 'just' bleeding...and it gives many a problem. Try the method above...there are a few others that work too.

Bleeding cold works well too.

Car cold...cold as in the a.m.

Fill ET to between min and max level.

Close ET and bleeder screw.

Key to position 2, fan on low, heater on highest temp

Start car and rev to 3-4,000 rpms for 20 secs. and Turn car off.

Check level.
Add coolant as needed (to between min and max)

Repeat as necessary.

The revving knocks stuck air bubbles out of the system.

Unless you've overheated yourself or got the car recently, it's probably not the head gasket...but what is your prior history with the car and overheating...if you have any?
 

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I have read OP***8217;s previous posts on this topic.

He knows all about bleeding properly and has bled it several times.

Improper bleeding typically doesn***8217;t lead to ***8220;bursting***8221; of the overflow tank

OP recently bought this car used and doesn***8217;t know much about its history.

Given all the parts he has thrown at it, a simple compression test will help a lot in ruling in/out a head gasket problem at this point.
 

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A compression test will hardly tell you squat on a blown HG. He needs to perform a leakdown test and see if he gets air blowing out of the intake or exhaust or cross-cylinder.

I'd start w/ the more obvious things first though like bleeding.

Take a look at this masterful 2013 gem

https://forum.e46fanatics.com/showthread.php?t=997377
 

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compression test is an instantaneous snapshot. how well a cylinder, head, valves seal at an instant. but if you have a small leak or a gradual leak, such as in the case w/ a hg, a leakdown is better. plus you can easily just hear the compressed air escaping where it shouldn't (adjacent cylinder, muffler, or intake box)
 

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OP,

Do you really want to find out the root cause of this overheating problem? Do you have 20 minutes to spend? No Rocket Science degree required:

0) did it overheat when car was moving above 50 mph?
1) Hood closed; with every components installed as normal, idling the car and keep watching the temp gauge until it reach 12 o'clock position or a little over (a better way is to use dash OBD display and wait until it reached 93C) . Shut engine off before it reaches overheat zone.
2) Does the electric fan turn on?
3) reach in and hold the radiator lower hose. Is it hot or is luke warm?
 

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I have a 2003 325i. I have replaced the overflow tank due to it bursting, the water pipe hose, the radiator, the water pump, water pump pully, fan clutch and fan blade. Somehow my system is still getting hot despite my being sure that each new part would solve the problem... what next? thermostat? seems like the only thing I havnt replaced due to it seeming to open and close just fine.:thanks::thanks::thanks::facepalm:
sounds to me like you have air in your system. To get the air out, keep filling the expansion tank with coolant(have a funnel because it will take a while for the coolant level to lower). There is a little screw on the upper coolant hose that lets the system breath, un-screw that so that when its being filled the air in the system will be released. do this until all air bubbles are gone, then put everything back together and take her for a spin.

there are videos on youtube that i recommend you watch.

best of luck
 
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