Daihatsu Skywing - Getting air out of the cooling system

Changed my coolant after an unfortunate overheating incident during inspection, and am having trouble getting air out of the system.

I’ve tried letting the coolant expand into a funnel jammed into the rad fill port, with the car on a loading ramp with the front jacked up. No joy.

I’ve also tried applying negative and positive pressure with a 150NT “drain buster” vacuum pump (“WORLDS MOST POWERFUL PLUNGER” Ooer Mrs).

That didn’t work either.

Another Internyet recommendation is to try and vent air via the heater matrix connections. Didn’t try this earlier because I thought they would be rather inaccessible.

Just had a look and…er…the heater hoses to the matrix are indeed not very accessible, because there don’t seem to be any.

Just call me Master of Understatement.

Or Blind As A Bat

COULD still be missing something, but the engine compartment is fairly spacious (In sharp contrast to god-awful modern cars I’ve looked at) so I don’t see how.

I assume heater functionality, if it has any, is done via the aircon, which isn’t AFAIK, connected to the cooling system.

Is this plausible? Never had an aircon equipped car in the UK so don’t know what the norm is.

AFAIK this is a Taiwan-only car so it COULD be local weirdness, but I’d be surprised if they deviated greatly from general Daihatsu design norms.

Drill multiple holes in the highest areas of the engine block you can access, should help the air escape.


Fuck off.

Have you tried removing the cooling system?

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See above

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OK. Confirmation, if it was needed, that Forumosa these days isn’t much good for automotive stuff, one of the reasons I stopped using it after the “Brexit of Bulletin Boards” platform change.

But I’ve started so I’ll finish this one.

Next steps are

(a) Apply sink syringe vacuum with car on the ramp/jacked up.

(b) Apply more SERIOUS vacuum using a fridge compressor (will need some plumbing improvisations and caution since it seems ipotentially damaging)

© Give up and let it clear itself (also potentially damaging).

Not sure about

(d) Boiling the coolant by disabling the fan.

Seems risky, but it’ll happen at idle, which may be less risky than normal operation with an air pocket in the cylinder head.

I think normally they remove the coolant and than putting it back. I’ve seen them do that with the fridge. It’s the same with home aircon. Remove, clean pipes, put back.


This is the “Post-putting-it-back-bit”, trying to get rid of air in the system.

But this is the engine cooling system, not the aircom system.

The aircon worked when I bought the car but I havn’t used or maintained it so it would need some filling and fettling now.

Not a priority.

Cooling system will get rid of air by itself normally. You have the overflow at the radiator. Taking of the pump could help, draining the whole system.

Might get away with just letting it clear itself, but its potentially damaging (as I wrote above) since an air pocket is likely to cause a hot spot.

The system has been drained and refilled once. Not sure how to improve on last time. Refilling on the ramp MIGHT be a bit better.

I think when refilling you should do so with the motor running, this way the water get pumped around. The thermostat of your cooling system will open when too hot.

(e) If those don’t work, try turning the car upside down, could also find a gentle slope and slowly roll the car down the slope with the engine idling.

(f) Put the fridge on top of the car and extend the radiator hoses so that the radiator itself can be placed inside the fridge on the roof. Get some solar panels or perhaps a generator to power the fridge.

(g) As suggested above, remove the cooling system. This may limit journeys to quite short distances in order to avoid potential engine damage however it would result in a significantly lighter vehicle, this combined with the slow speed should provide much better fuel economy and could potentially fix the previous fuel flow problems.

(h) Remove the engine and cooling system. Again, this may limit journeys to quite short distances however it would result in a significantly lighter vehicle, this combined with the lack of an engine should provide 100% fuel savings and fix the previous fuel flow problems.

Let us know how you get on.


These all sound like excellent courses of actions. Sounds like @Ducked will be busy for the next few days. If none of the above yield the desired results, try the following:

(i) Dispose of the cooling system, engine, body and wheels of the vehicle. Reattach the compressor to the fridge and replenish the fridge with plenty of beer. Once the desired cooling has been achieved, celebrate that you got rid of the piece of crap and don’t have to deal with it anymore.


See above

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I decided to try boiling the coolant, pulling the fan relay to disable the fan. It boiled when the funnel in the radiator was almost brimmed, and it did so fairly violently, so I lost quite a lot.

As the remaining coolant retreated into the radiator with engine off, I topped it up with fresh. I was going to do a few cycles of this but didn’t have enough spare.

If I’d thought of it I could probably have reduced coolant loss by removing some of it while it was expanding into the funnel, before it boiled

Took the car for a longish run and there was no sign of blowing from the reservoir, so it looks as if boiling your coolant is a way of getting stubborn air out of the system.
Unclear if this cure is worse than the disease, though. I’d think not, but if I’m wrong that’ll likely be why I’ve never seen this procedure recommended.

You can buy special deep funnels (at least in the US) specially for filling the cooling system, which would reduce coolant loss. You probably can’t get these in Taiwan, but I bought a bigger funnel, which doesn’t fit the radiator port, but it does (just) fit in the funnel I used previously, so I could “stack” them.

However, if there are no further signs of trapped air I’ll leave that for the next coolant change, if there is one.

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It sounds like part of the issue may be the circulatory pump running whilst the water is boiling. The positive pressure from the pump is adding to the boiling water static pressure leading to a violent eruption.

Rather than using the running engine to heat the water to a boil, and hence to an eruption, it may be better to use an external source and not have the engine running,

Some lessons may be learned from those living in particularly cold climates, mostly in the past, but still carried on in some locations, so it may require speaking to older members of those populations whose memory may not be optimal but nevertheless a survey of a sufficiently large sample size should yield the key points. In those older times it was often necessary to start a fire under a vehicles engine in order to sufficiently warm it and it’s fluids in order to start. A similar approach could be taken with the Skywing, light a fire sufficiently large to heat the cooling water to a boil but obviously not so large as to set the entire vehicle on fire (that would be a travesty), watch those trapped air bubbles fly to freedom!


The issue of the funnel is easily solved, one of these can surely be purchased locally and will allow more than enough head room for expansion of the water. If it doesn’t work well there’s always the alternative of sticking it up your you know whatsy and contemplating alternative solutions while ingesting and purging fluids of your own.


Come back and let us know how it went.

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See above

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Don’t fancy that much. It implies running the engine with the system dry initially, which seems to risk cracking the cylinder head at the exhaust valves.

I’m also not clear that it’ll help get rid of trapped air, but if it might, it’d be safer to try turning the engine over on the starter. With a petrol engine you could remove the spark plugs to reduce the load.

No, you start filling water it and than you start the engine.