Bubbles in the Rad?

[keltik]

Its not a big problem but i'd love to know what causes it.

Waimaks noticed this on his EA82T after a coolant flush;

 

With radiator cap off and engine running, the coolant sits at a steady level in the rad. But if you rev up the engine - the level drops as the throttle is opened and rises again as soon as the throttle is closed. As the engine is winding back down to idle, bubbles appear at the rad cap as if there was a scuba diver in the rad letting out a few breaths. Theres no over-flowing or dramatic coolant spraying everywhere, just bubbles. :-\

 

Now you may be tempted to scream "BHG Fool!" but i ran the same test on my Honda wagon, the family Merc Sprinter, my bro's Toyota and got the same results. I repeated the test over 10 times and each one i got bubbles, where's the air coming from? Does this happen to you? Am i crazy?

 

KELTIK

 

p.s - i should mention none of the aforementioned vehicles have any known mechanical issues.

[Loyale 2.7 Turbo]

Well...

My EA82 Carbed, Did Exactly the Same... All of this is normal on it (I Think) maybe except for the Air Bubbles.

Remember: the entire coolin´ system, got two circulations Just as a human heart: the primary circulation (Main Engine) and the Secondary (The inside dashboard heather to blow Hot air inside). I got those bubbles long time ago, and then they go away the day I decide to make a "Recirculation" on the secondary, due to this two facts: Here in the Tropical caribbean, we don´t need hot air (Atmospheric air usually is hot, almost always... except for just december & January) and the Air Conditioner will cool better without anything hot (Like the inside radiator) near of it.

You can try to open the Heather control on your Subie´s climate control to Hot, and then repeat the test.

Also those bubbles can be made by the water pump, when you accelerate the engine without the cap on radiator, the water pump will "Suck" a Li´l bit more due to acceleration; and induce air to get onto radiator, and when it gets to idle sped again, the air that got into, comes out as bubbles.

If it is the case, you must got a bad thermostat, or no thermostat at all.

I removed the Thermostat of my EA82 long, long time ago... in the past millenium... 1993... due to overheatin´ troubles...

Well... I hope this could help ya to understand where bubbles came from...

Good Luck!