96 Rover Mini Cooper SPi - Coolant Volume Question

[Snoop]

Hello - I had to replace the 3 way rubber hose between the thermostat, inlet manifold and heater today and prior to doing this, I drained the radiator by removing the cooling fan temp sensor at the bottom of the radiator. I fitted the new 3 way hose and then filled the radiator & engine with approx 2.4 litres of new coolant right to the top of the radiator cap. The manual say's the coolant volume is 3.55 litres therefore it seems strange that it only took 2.4 litres of coolant.
 
I started the Mini and ran the engine for 10 minutes at idle with the heater valve fully on then I checked the coolant level which remained unchanged. Is this correct? When you drain the coolant by removing the cooling fan sensor at the bottom of the radiator, does approx 1.15 lires of coolant still remain in the lower part of the engine cooling system?

Any help with this would be much appreciated, cheers

[Peter Laidler]

The 'lost' coolant could have remained in the heater system - the hoses and heater matrix.

[Snoop]

Good point Peter, thanks for that. I assume its best to run the engine for 10 min's or so with the radiator cap off so that any air bubbles can get out of the coolant system?

[Peter Laidler]

I've only had mine apart once and that was when it was brand new, to replace the water with waterless coolant. That's when I noticed that it hadn't drained down fully. I tried to blow the heater hoses and matrix clear with an air line but once there was even a small air gap, that was it! So just undid the lowest heater matrix hose, put big bowl underneath and let it flow.

Don't forget to protect the carpets!!

My rad cap is now just a simple unpressurised cap

[Snoop]

Thanks Peter

[minibitz]

Pulling the temp sender from bottom of rad only drains down the radiator.

Coolant level in block & head only drops down as far as where bottom hose attaches to the water pump. To empty the block fully you would need to tip it on it's side. Hence why cooling system doesn't need a full 3.5l for refill.

[Snoop]

Great, thanks for that information which all makes sense

[Snoop]

Great, thanks for that information which all makes sense