I think i have a air lock in the rad of my bmw520i

Loosen the cap on the rad and run the engine up to operating temperature. Make sure the rad is full, and go for a short drive around the block to warm up the engine. Make sure the heater is turned on high and the fan running full. There will likely be some burping and gurgling going on as the air gets forced out. Keep checking and topping up the rad. Eventually it will stop.You should run it for acouple days with the cap loose to be sure all the air is out. After that, make sure the rad is full, close the cap and top up the overflow bucket.

the most commen problem with no heat is an air lock in the cooling system
when the vehicle is cold remove the rad cap
then there is a air bleed screw on the coolant pipe that goes across the front valve cover open the bleed screw about 3/4 to a full turn
use a funnel and over fill the rad into the funnel (this will make a mess)
make sure you have a steady streem of coolant coming out of the bleeder when you have a steady streem close the bleeder then there is a bleeder screw on the thermostat hosing open it and when you have a steady streem from it close that one then put the rad cap back on
and start the vehicle put your heat controls on VENT ,HOT AND HIGH BLOWER SPEED
run the vehicle and make sure you have HOT AIR COMMING OUT OF THE VENTS NOT WARM if its just warm then shut the engine off and open the bleeder on the pipe not the T-STAT HOUSING
keep repeating till you get HOT AIR COMMING FROM THE VENTS
top up the over flow bottle the rad will be fine
hope this helps

could be the thermostat also could be air locking in the heater hoses as well as the heater controll valve is malfunctioning

hi, the most obvious cause of no heat coming through the heater vents is going to be that the thermostat has gone and will need replacing these are cheap to buy and not to hard to fit.

Now the other problem you could have would be with the heater controls the control that chooses hot or cold air may have packed up and may need replacing the best way of finding out it the thermostat has stuck shut is to feel the top and bottom of the rad when the engine is nearly up to temp dont burn yourself just give the rad a feel at the top and bottom and see if the heat is even all around the rad.

If you look at the two pipes going through the center of the bulk head towards the middle these two pipes go to your heater rad matrix now if only one of these is warm and the other cold then this means thermostat gone if how ever all the pipes are hot and the rad is hot all over then this would point to the heter controls being at fault.

Now if your heater controls are cable one of these may have broke and you would see this once you have the cover off the controls if how ever yours is electronic then the chances are you wont be able to tell if its working or not.

I myself would go with the thermostat first as this is the cheapest and easiest part to change.

Let me know how you get on or if you need further assistance ok

it may have a blown head gasket if it keep over heating or there could be just an air lock in the cooling water,, you will need to bleed the air out to stop the over heat as the water is not going around the engine its not opening the thermostat so it cant bleed its self take off a water pipe thats the higest pipe you can find it may have a bleed vent in a pipe were you can bleed it from ,,,top up the rad and header tank take off the bleed nippel when water with no air is coming out and the jobs a good un? run the motor for a time or go for a drive to check its not ever heating again and the heater should by now be blowing hot air,, top up the rad and header tank when its coold down

blower might be gone

Is the air actually blowing into the car?But it's just hot?It sounds like your blower motor is not turning to blow air.you have a fuse,check the switch that controls the blower,and the blower motor it self.

time to buy a new radiator
yours is clogged

I think you could be right about there being air trapped in the system.
Or the heater core(radiator) is plugged.
Either way you need a pressurized radiator coolant pump to put the coolant in without air being trapped.
Although,i have seen it done by jacking the vehicle up high enough that the radiator was now higher than the heater core level, and then the coolant was put in.
But this is dangerous to try.

Yes, you re correct! thats a thermostat issue.