EJ25 air in coolant system

[mad max]

Sometimes when I come back from a flight and power off to idle and make a steep 60kt decent and land the low coolant alarm comes on during decent. The coolant overflows into the overflow bottle and requires another bottle drain to correct level, top up engine and bleed before next flight. It will fly all day on 88 deg. until next landing. Got her in the hanger untill I sort the problem. Any ideas would be appreciated.

[aussie_paul]

From what height and how long a descent Max?

Aussie Paul.

[mad max]

From about 800 ft idle all the way at 60 kts and touch down.

[RossM]

unless you are only getting enough air flow through the radiator with the the prop sucking air through it,, and not enough air through the radiator when idling and with the oncoming air around the pod/engine.

[mad max]

Interesting comment Ross. I'll look into that

[mad max]

You got me thinking Ross. I believe the radiator cap marked 90deg. during decent because of lack of air flow through the radiator is opening prematurely and allowing coolant to fill the overflow bottle and allowing air to suck back into the system before it closes. I'll go buy a new cap with maybe a higher setting

[aussie_paul]

You got me thinking Ross. I believe the radiator cap marked 90deg. during decent because of lack of air flow through the radiator is opening prematurely and allowing coolant to fill the overflow bottle and allowing air to suck back into the system before it closes. I'll go buy a new cap with maybe a higher setting

Might be just a faulty cap Max, should not need higher temp/pressure.

Aussie Paul.

[mad max]

Yes Paul I just realised the 90 number on the cap prob. stands for pressure and not temparture

[Tim]

G'day Max. All modern automotive cooling systems are under a higher pressure than earlier engines, completely regulated by the radiator cap. 0.9 bar = 90kPa or 14psi, 1.1 bar = 15psi or 108kPa, and 1.3 bar is around 18psi or 124 kPa.
The 90 on your cap must be kPa which I would suggest is probably a bit low for a modern engine. If you throttle back quickly while under load (reduce the water pump circulation) the coolant can boil locally around the top of the cylinders or head causing it to push water out.

[tonydenton]

the forum moderator has let me back on and I have been wanting to ask the gurus . yes tim. . many years ago when the ej2.2 were being used they had the air in the top of the engine problem. I have a long term ej22 project and need to ask how or what was done to solve that problem please.

[mad max]

I seem to have solved all my EJ25 coolant problems by replacing the cap. Plus anytime I refill The coolant from empty I make sure the little hose behind the intake manifold is bled well before refitting