I need some info on my 520i that i just bought

What is this cap on?? Radiator or windshield washer reservoir? Something else?

If the radiator, most newer cars have a plastic bottle or tank that has a "cold" and "hot" level indicated. You should be able to see the coolant level thru the tank. You should NOT need to open the radiator cap if your car has this tank. Add a 50/50 mixture of water and coolant (of a type your car requires) up to the "cold" mark and start the car. Let it run with the heater set to HOT and fan set to HIGH. Continue adding the 50/50 mixture to maintain the coolant level to the HOT level mark on the tank as needed with the engine running. Stop when there is HOT air blowing out of the heater.

If your car does NOT have this tank, you may only open the radiator directly when the engine is COLD. Wait several hours for the engine to cool after shutting off before attempting to remove the cap.

When cold, press DOWN on the cap WHILE turning. Most caps will come off after a 1/4 to a 1/2 turn. Start the engine and set heater HOT and fan to HIGH. Continue to add a 50/50 mixture of coolant to the radiator until the heater blows HOT air. The coolant level in the radiator should be just under (1" or less) from the bottom of the radiator opening.

Was this the info you're looking for?

Have a coolant pressure test done and compression test done. There is a real possibility of a cracked head but you may be lucky with just a warped head and blown gasket.

You might need to fluss the radator out with a hose pip. take the botom hose off and take th radator cap off. then crank the car up. stick the water hose in the top of the radator were the cap you took off and let the water run throu the radator for feww min.

here's how the the cooling system on your suv works, when the coollent reaches a sertain temp the it will build pressure in the system the pressure will open the radator cap and will either push un needed coolent into the resevore or take coolent from it. if the level in the radator is fine and the coolant level in the resevore is fine then there should be no problem but if your still having problems try having your radator cap pressure tested.

an easy way to do that is take off the radator cap or over flow cap and start the moter turn your heater to high and put it on defrost once the bubbles stop coming out your done.

First check the coolant level and refill. Now drive it. Once car cools off recheck the coolant level. If it is down you may be holding air in the engine block that needs to work its way out. To do that with the radiator cap off start the car and be ready to addd a 50/50 water/coolant mixture to the radator while the car is running. Just need car to get to normal operating temp so the thermostat opens and allows the free flow of coolant throughout the cooling system. If the coolant level is fine but the car continues to overheat the most likely cause is a bad thermostat. Replace it. After that the next items to look at are the water pump, the electrical cooling fans (if you car has them). .

If you have owned this vehicle since new and followed the service maint program, it will be fine. If you purchased the vehicle used, and dont know what needs to be done, check with the owners manual. If you dont have the manual, replace the fluids, oil-filter, coolant, transmission, and also have the brake fluid tested. 100k tune-up, with plugs and wires. fuel filter. Have the belts checked for cracks, more than 5 per inch should be replaced. Have the brakes and exhaust inspected also. It may seem like a lot of money wasted and work, but the more maint you have done, the less you generally will have on expensive repairs. Craig

is there any water in your oil or oil in your radator or do you get bubles in your radator when cap is off and motor runing if so then its your head

Not quite sure what your question is but if your looking for an opinion here's mine.
Even thought you didn't find the normally sign's of a blown head gasket you need to be aware that a cracked head can cause the same issues that a blown head gasket does. Also it is possible to have a problem with either of those two things and not involve the cylinders. A breach between the water jacket and the pressure side of an oil port would force the oil into the water jacket. Since the spaces traveled by the oil are relatively small the transfer will tend to be one way.

However this is an uncommon problem. About all you can do to test for it is to check the oil pressure with a gauge and compare that with specs.
I would probably check it to be on the safe side.
Hope this helps.

i change the radator get a new one it fit the problem