I am having problems refilling my coolant after I drained it today. I disconnected the bottom hose and let the fluid drain out and then let some distilled water run through it. I then loosened the hex vent screw ( many place say it should be a phillips screw) and started to fill the fluid slowly while the car was on, but it took forever to get the fluid down. At one point there was alot of bubbling in the expansion tank then a lot of coolant when down, but at no point did I see bubbles come out of the screw. I dont want to drive it while there might be air in there. What am I doing wrong? 1 gallon of fluid came out and I put 1 gallon of fluid in.

FYI: My heater does blow hot air

 

I thought maybe letting the car sit overnight would help but it didnt. So i drained all the fluid again and tried it a 2nd time. Still same result. I drove the car around the block and came back and loosened the vent valve, but that didnt help. After I turned my car off, it sounded like something was pumping ( water pump? ). But the coolant levels in the tank did not change. When I press the lower coolant pipes ( the pipe I drained the fluid from) they seem to have very little fluid, but each time I squeeze the pipe air bubbles come out at the coolant tank. This seemed like a very straightforward procedure, which I have done on other cars, but they always had a radiator cap and a reserve tank.

 

According to the service manual, you turn the heater on high heat, low fan setting (ignition on). Remove the bleeder/vent screw on the thermostat housing. Fill through the expansion tank until bubble free coolant comes out the vent screw. Then close the screw and let the car idle until you no longer see the level dropping in the tank and set it at the max level.

Did you ever get coolant out the vent screw?

 

I followed those steps exactly. But when I remove the vent screw nothing comes out ( i actually just stripped the vent screw and to get a new one Monday). The coolant never once bubbled nor did I hear at at the vent screw. I thought maybe the thermostat was not opening up to let coolant in, so I hooked up my laptop to my car using those OBD cables to monitor to temp. I let the coolant temp get to 200 degrees thinking that would open the thermostat, but nothing happened, the fluid stayed at the same level.

 

For my Z3 I had to jack up the front corner of the car in order to get the radiator (where the bleed screw was highest) a bit higher up for the bleeding process. Not sure if it will help for the MINI, but keep at it.

 

I drove my car around for 20 miles while driving with my laptop and OBD plugged in. My temp never rose over 220 and this was after hard driving then resting at idle. Plus my heater works perfect too. My bottom coolant lines were cold when I started my trip and hot when I ended. Could it be that everything it fine?

 

If one went in and one came out, you should be fine!