Please help!!! Coolant Level is Up and down!!!! Z3 1.9L

Hi,



I hope this is the right place for this sort of issue!



I have replaced my radiator on my BMW Z3 2000 plate 1.9L, the system has been bled and is producing amazing heat in cabin and showing no signs of overheating, temp needle sitting at normal 12 o'clock.



I have also had the system pressure tested, head gasket tested and all has come back fine although i am aware that bad head gaskets can sometimes not show up.



My problem is that my coolant level is all over the place 100 miles down the line from Rad replacement. I have been constantly checking the coolant fearing that it will either over spill or wont be enough in the tank.



I will use Sunday, Monday, Tuesday and today as an example;

• The system is bled by me filling it up until all bubbles have stopped coming out of the bleed hole, I then put in the bleed screw in and tighten. I then top the coolant off to the cold mark level before starting the engine and put the cap on. Once it gradually gets up to temp and the heat is warm and it contentiously gets hotter in the cabin. The coolant level rises an inch or 2 once its reached normal temp at idle after 20 mins or so.


• I then take the car for a drive 2 miles or so and park up to check my coolant level and notice its gone a good inch or so down below the cold mark but I still have amazing heat and the temp needle is still at normal temp 12 o'clock. I believe at this time I haven't lost any coolant as previous to this I have released the bleed screw and the tank fills up to the top with coolant. So I drive it home and leave it over night to cool completely off.


• The next day I check the coolant level whilst the engine is stone cold. The level reads about half an inch maybe an inch from the bottom of tank. I read on here that no matter what the coolant level should sit on the cold mark when the engine is stone cold to be at the correct level for the system. So with that in mind I take the cap off and top it off to the cold mark. I then start up the car and wait for warm air in the cabin, once I have warm air I check the coolant level and it has not really risen up as the temp is about a 1/4 of the way from normal temp 12 o'clock.


• At this point I take the car for a drive about 2 - 3 miles and pull up to check the coolant level. The level has risen from the cold mark to just below the warm mark on the tank and the car is at normal temp 12 o'clock kicking out amazing heat. I then do this lap again and pull the car up on my driveway to check the coolant level. The level is about 2-3 inches from the top of the cap on tank, the temp needle is still at normal temp 12 o'clock and is still kicking out amazing heat.


• At this point I'm confused as I'm not sure if the level is meant to rise that much "this is because of the warm mark on the tank". I then call it a night to let the engine cool down so I can check the level in the morning.


• I check the coolant level this morning and as predicted and hoped the coolant level had gone down but not to where I expected it to. It was about an inch above the warm mark on the tank. I started the car and gave it a couple of good revs and then checked the level, the level had dropped about half way between the warm mark and the cold mark. Again this baffled me as I'm now very confused.

I guess the questions I feel to ask are;

1. Is the coolant meant to rise as high as it did last night "2-3 inches from the top of the cap on tank"? If not what's going on?


2. Is the coolant level meant to drop back to the cold mark every single time after the engine/system has cooled down completely? If yes then why is mine not?

I think that will do to start, apologies for the run down, any info/knowledge on this would be well appreciated.



Thank you in advance

Please help!!! Coolant Level is Up and down!!!! Z3 1.9L