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Air Locks – Bleeding

Mod Description
An air lock in the coolant system can cause overheating of the engine, a cooked turbo or just lack of heat from the heater. Lets get rid of it.
Mod Details
PremiumNo Difficulty Mod ID133 CreditVarious For450 Fortwo451 Fortwo452 Roadster Link Copy to Clipboard

This information will show you how to force the airlocks from a:

Fortwo 450 600cc,
Fortwo 450 700cc,
452 Roadster,
Fortwo 451 turbo,
Fortwo 451 non turbo,
Fortwo 451 Diesel.

How Do I Know I Have An Airlock?

Generally you will get no hot air from the heater even when the heater blobs apear on the speedo.

The big indication is if it reaches 3 blobs too quickly or reaches 4 blobs during continuous driving.
In my experience, it takes about 7 minutes to reach 3 blobs with normal driving conditions.

If the engine is ticking over it will heat up very slowly.

If the car reaches 5 blobs then you will hear a warning sound and you will know you have a problem.
Pull up and stop the car at the first safe place and turn off the engine.

What Temperature Will The Alarm Sound At?

120 Degrees Celcius is the temperature required to show maximum temperature on the speedo.
The alarm will sound moments before the last last temperature indicator comes on.

Doesn’t Water Boil At 100 Degrees Celcius?

Indeed it does but there are 2 things that increase the boiling point.
Firstly the additive brings the fluid’s boiling point up to about 110.
Secondly the heating of the water causes expansion which in effect causes pressure.
Pressure increases the boiling point to about 120 degrees C.

That is why there is a minimum and maximum mark on the header tank. Too little water and the
pressure won’t build up properly plus there is more of a chance of pulling air into the system. Too
much water and there won’t be enough air in the header tank to create the pressure.

If the coolant exceeds its boiling point the molecular bonds break down and bubbles appear in the same way they do when you boil a kettle. The air can get trapped causing an air lock and the engine can misread the temperature.

Airlock Removal Fortwo 450


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