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I've encountered a recent overheating issue that has left my car undrivable for over a week now. I've replaced a hose, thermostat, and water pump. Checked for head-gasket issues (there were none). Fan and fan clutch are functional and it still overheats. The part that gets me puzzled is when the thermostat opens up and lets the coolant hit the radiator, the hose leaving the radiator is cold. My first thought was "clogged radiator" I tested that theory by inserting a garden hose into the top inlet to the radiator and checking for water escaping from the bottom outlet, and it did at the same speed it entered. So as of right now I've darn near replaced the whole cooling system and it still isn't functioning as it's supposed to. I've got a 1997 328i
 

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I've got no aux fan I busted it in my accident :emo but I just filled the system with coolant, let it run, filled again, let it run, ect. I don't know what "bleeding the system" is.






10) It really helps to have a friend lend a hand by sitting in the car revving the motor and keeping an eye on the temp gauge. Start off by removing the coolant reservoir cap and the plastic bleeder screw right next to it. Fill the coolant reservoir with a 50/50 mix of coolant and distilled water. Have your friend start the car, turn on the heater to full hot on the vent position and rev the motor to about 2500 RPM, if the temp gauge goes past the 12 o'clock position, shut the motor off, let it cool down and start over again. Watch the coolant reservoir, as the engine warms up the coolant level should drop, refill as the coolant is sucked out of the reservoir. Watch the bleeder screw hole also, when coolant with no air bubbles begins to overflow then you're almost done. It's a good idea to have some paper towels handy to mop up any overflow. Screw the bleeder screw back in (be careful to not break the plastic screw) and continue to rev the motor, you should see a continuous stream of coolant spraying in to the reservoir from the small hole at the top. Continue letting that spray in to the reservoir while your friend revs the motor for a couple of minutes, until the gauge hits the 12 o'clock mark, to ensure any remaining air is gone. If the heater is blowing hot air when you're revving the motor AND when the engine is at idle then your cooling system is properly bled. If your vents are blowing cool air at idle then you still have air in the system, try revving the motor more and/or squeeze the radiator hoses to help dislodge any trapped air. Once your system is fully bled, top off the reservoir and replace the cap. Check the coolant level in a day or two and top off as needed.


jb :)
 

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FYI - just finished using this procedure on my friends '02 320i and it worked well. Got all the air out and he's got heat again.

Thanks.
There will be times when you encounter a stubborn air pocket in your system that will just not purge, and a one time bleed is not enough.

Do the bleed when you load the coolant. Start your engine and let it warm up to where u see the engine temps rise to normal. then bleed again.

There were times i have had to bleed 6 times to get it right. But squeezing on the radiator hoses while bleeding will help to purge out the air.

lotsa' luck
 

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Poured water in the upper hose,coming out at the same flow from the lower hose. bled the system several times. during bleeding heater is on ,blowing cold air anyways. Also took thermostate out .still overheats comments PLZ.
 

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It took me about 45 minutes or so to bleed it, just keep it bleeding and make sure there's hot air coming from the vents!


Yes.......sometimes those air pockets can be very stubborn! Great to hear you got it sorted!



jb :)
 
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