Another yell out for help,

My 525i 2004 is starting to turn on rough in the morning for few minutes and will lose about 200-300ml radiator coolant every 1-2 weeks. Guys have done a pressure test and could not find out any leaks. Any suggestions???

Cheers.

Maybe it is going into the block - head gasket? They can do a test where they check for the presence of combustion gases in the radiator.

Do you have smoke from the tailpipe?

White smoke? It would have kind of a sweet smell. Any visible leaks? Coolant on the garage floor?
Check the cap, is the seal looking good? Coolant can evaporate with a bad seal, but I doubt it would be 200-300ml/week.

The radiator could have a VERY small leak around the welds. It's happened to me and a few others. No coolant or drips on the ground yet I was losing a liter or so every 2-3 months. Lifted it up and was able to spot a lot of white dried up coolant on the radiator.

I had a slow leak at a coolant sensor on the lower radiator hose. Mine had a bad o-ring. There maybe two sensors (my 545 has two) so not sure where yours may be located but find them and check for leaks if any, preferably after a drive out.

Check the expansion tank. Cracking here is very common. Also the upper vent pipe along the top of the radiator. Mine cracked at the connection leading into the radiator. Good luck.

Check heater core as well for a slow leak. Look under driver and passenger side carpet or do a block test.

+1, had mine replaced about 6 mos ago, along with a few hoses.

i had the same thing. radiator had a tiny leak. i replaced it myself.

then later on, the auxiliary fan was leaking a tiny bit. had indy mechanic take care of that while he was doing my oil change.

Thanks guys, I found out, the expansion tank has a hairline crack and I think it is because of the mechanic I was using before, he on number of ocasionns in the pas while checking the leak would fill either just water or just oil, not a mixture and that too when the car was hot and turned off. Not sure if that build the pressure due to wrong liquid level, will change the tank and see whats next.

good work. :thumbsup:

or you can silicon seal it.