Radiator mounted expansion tank:
1. Loosen the bleed screw on top of radiator expansion
tank and let the coolant flow out as you pour it in the
reservoir. Tighten the screw when the flow out is free of
Separate expansion tank:
1. Loosen the bleed screw on top of thermostat housing
and let the coolant flow out as you pour it in the reservoir.
Tighten the screw when the flow out is smooth and free of
2. Set the temperature setting to full warm and start engine.
3. When the car is going to reach his normal temperature you
might going to need to add more coolant. Always check the
4. With engine idling at normal temperature, open the bleed
screw and tighten it when coolant is spilling out smoothly
and free of air bubbles.
5. Repeat bleeding, and again and again.
6. Do it a few times to avoid overheating.
M20 Bleeding experience by moots:
Just to share a simple method to bleed the cooling system.I
really cannot comprehend why we need to bleed,bleed and re-bleed
the cooling system after every maintenence.I did this after
replacing the thermostat and flushing the coolant:
(Mine's an m20 engine with the reservoir by the side of the
1.Fill up the rad with the plastic bleeder screw(on reservoir)
and metal bleeder screw(on t-stat housing),open.
2.When full,put a finger over the reservoir bleed hole and
blow,yes,blow into the reservoir filler neck.(we are basically
pressurising the system)
3.When water flows out of the t-stat housing bleed hole,tighten
4.Top up reservoir if required.
5.Now blow again until coolant exits the reservoir bleed hole
and tighten when bubble free.
6.Top up coolant to the cold/kalt mark,tighten cap.You're
done. No more bleeding required as all air is purged from
the system. I have done this 4 times on three cars and it
worked like a charm.