pressure in cooling system

Hi All I have a 1997 E39 528i, and I am having problems with the cooling system. I;ve just changed the radiator a couple of days ago, and bled the system a couple of times. The funny thing is that, after running the
car for sometime the coolant level goes down, and stays down even after the car has cooled down overnight, and the minute I open the cap, when cold, the level goes up and you can hear the pressurised air coming out. At this moment if i leave the car running it overheats. I let it cool down and bleed it again and things run fine after that. However, if I re-open the cap the second day when it is cold the same thing happens again, the coolant level rises up and it will over heats if I drive it, and will only be ok if I bleed it again. Is this normal, or do I have a blown head-gasket, or is it just a bleeding problem. There is no leak in the cooling system and the coolant is not used up.
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snipped-for-privacy@hotmail.com wrote:

I had the same issue witrh my E34, M50 engine. Turned out that the head was cracked in three places, and exhaust gas was getting into the coolant. I was losing a little coolant though. J.
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http://www.pelicanparts.com/bmw/techarticles/E36-Coolant_Flush/E36-Coolant-Flush.htm
Kyle. 98 740iL 01 525i
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Thnaks guys for the info, I bled the system again while the heat was on, tomorrow I will tell you if this works or not. thanks again
Kyle and Lori Greene wrote:

http://www.pelicanparts.com/bmw/techarticles/E36-Coolant_Flush/E36-Coolant-Flush.htm
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I bled the system a couple of times during 3 concecutive days in the morning, and now it is working fine. I had no idea that bleeding the E39 is such a pain in the neck. the best thing to do in order to know if your cooling system is not bled well is the following:\ 1- there will be lots of pressure in the hoses while the car hot, solid like a rock. 2- it will heat up upon driving after opening the radiator cap even when cold. 3- the coolant will go down in the rad when the car gets hot and not up. 4- a good sign after proper bleeding is that the hoses will not be pressurized while the car is hot, and when you open the cap when the car is cold, you will not hear any pressure release, and the coolant level will not change right after opening it.
Thanks again guys. This helped a lot.
snipped-for-privacy@hotmail.com wrote:

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