If you have an airlock the heater may not work very well and / or the engine may overheat.
The radiator can be drained by releasing the bottom hose connection. The cylinder block drain plug is on the rear face above the starter motor.
Bleed screws are located in the radiator top hose and in the coolant pipe on the front corner of the cylinder head. MINI One /Cooper have an extra bleed screw located in the heater hoses beneath the battery tray.
On refilling slacken the bleed screws, set heater control to max. temperature, fan speed low, which opens all the heater valves. Fill via the filler pressure cap neck closing bleed screws as bubble free coolant emerges. Now fill the expansion tank to MAX mark. Start engine and run at idle speed, until coolant level in the pressure cap neck ceases to drop. Turn off and top up to the top of the neck again. Restart, run up to temp then allow to cool completely and recheck all levels, repeat checks as necessary and watch out for any signs of overheating for a few miles.
(The Cooper S has the pressure cap located on the expansion tank so has a slightly different filling method. to One and Cooper)
The Following 2 Users Say Thank You to mab01uk For This Useful Post:
Use a long-life ethylene glycol based antifreeze (50/50 mix antifreeze water).
BMW coolant will definitely be right spec. but more expensive............
1st Gen. Approx. Coolant capacity 5.3 litres Cooper/One or 6 litres Cooper S according to Haynes manual.
I too could use a little more advice on getting rid of an airlock. I suspect my daughters Mini One 1.6 05 plate has a leak and has lost a lot of anti freeze and may be airlocked. It has been overheating and I only looked at it first time tonight.
It already had new thermostat housing and water pump under warranty.
Tonight I managed to open the bleed screw on the top radiator hose - no water coming out. I could not get the bleed screw on the heater radiator hose open - do you need a special tool? I also could not see the bleed on the front right of cylinder block.
I ended up filling the exapnsion tank several times, and the level keeps dropping. There are no visible leaks. At the end I was squeezing the top radiator hose and could hear and see water being sucked from the expansion tank into the system.
Am I supposed to fill the system by removing the cap at the right hand side of the engine block, the one that is marked 1.1 bar and with graphical warnings not to open without looking at manual?
I would also say towards the end the temp gauge was not increasing with the car at idle but staying midway, although the expansion tank is now empty again until I get more anti freeze mixture.
The fan seems to be cutting in at both speed 1 and speed 2 so don't think I have the speed 1 failure issue.
Checked dipstick and oil looks good - no sign of water contamination and no obvious leaks around cylinder head gasket.
The expansion tank looks lower than the filler neck so I can't see how just topping that up would fill the remainder of the system hence why the technical service bulletin advises filling via the neck.
Gerogemac - I have checked other posts and can email you some instructions I've gleaned if you PM me with an email address
Another common but sometimes very hard to spot leak point is at the bottom corners of the radiator, often just weeps slightly. Also the heater matrix can leak unseen into the passenger footwell carpet but you would normally smell antifreeze inside the car if this was the case.
Note: The pressure cap on One and Cooper is at the gearbox end of the engine, between the cam cover and the air filter intake hose. It has (or should have) a yellow warning sticker about not opening when hot. It is sometimes difficult to open as it has the spring for pressuring the system, press it down and rotate anti clockwise. Fill the coolant here, then top up the expansion tank to the correct level.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.