interesting coolant advice for the 2.5s airbubble problem

[Subaru X]

talking with a crap load of subaru mechanics this week since I work with them I learned a few things about the cooling system. Mainly how to fill it without those blasted air bubbles.

 

Apparently the only thing the subaru dealerships do differently to fill up the coolant system is to fill it from the upper radiator hose.

of course you know fill it from the radiator, then remove the upper radiator hose from the radiator and start filling it up. Apparently this removes one huge air pocket. Thus no need to burp the system or worry about air pockets.

Don't know if anyone knew this just yet. But thought I would post it anyways since it seems to be pretty helpful

[Setright]

What are the odds?? I just suggested this method on another post....I heard it from a Sube mech too!

[blitz]

Help me understand better:

 

The coolant is poured directly into the engine through the top hose, and the system air is displaced out of the top radiator hose opening? Is the rad-cap removed?

 

I'm having a hard time trying to picture how this removes air from the highest part of the system (e.g. the area around the radiator filler neck). I'm not saying it doesn't, just trying to get a handle on why it works.

 

The best air removal I've achieved to date is warming and burping with the big funnel device and the front of the car elevated on ramps, but I'm still not convinced that I'm getting all the air out.

[avk]

On 1st gen. Impreza, the hose connects by the filler neck so in effect, you fill the engine block through the upper hose after the rad. is full. I wonder if there's any difference in 2.5l headgasket failure rate between Legacy and Impreza RS. Hard to tell because there are so many more Outbacks than RSes.

[Setright]

Blitz, remove the upper hose were it attaches to the radiatior, flex upwards and pour it straight down into the engine. Once fluid threatens to flow out of the hose, attach it again. Then fill through the rad cap opening. (Yes, I know this is the reverse order of the original post, but it works for me)

[blitz]

Thanks Setright. I can understand how the dealer tech's would be able to get the full amount of coolant in faster this way (beating the flat-rate is the game).

 

So with this method, afterwards you don't have to bring it up to temp with the cap off to chase out any remaining air?

 

Seems like even after I burp my system completely out, I still have to add another 8 oz. or so to the overflow after a couple driving cycles.

[Subaru X]

sorry setright is right. Fill the block first then the radiator. I would still try burping the system afterwards just to play it safe.

[Setright]

Of course! Fill block, fill rad, start engine, cap the rad when the fluid rises! Preferably nose up on a slight incline.

[blitz]

Thanks all.

 

Several months back I'd asked for info on a source for the "funnel device" thingy, and I'd like to thank whoever it was that put up this link:

 

http://www.drivewerks.com/catalog/shopcart/DWKS/POR_DWKS_toolsG_pg2.htm

 

I bought one of these and I love it. It allows me to warm the engine till the thermostat is fully open, and I can rev the motor and burp the top hose till the cows come home and all the bubbles stop, and not a drop of coolant is spilled (OK, maybe a drop). Really a fantastic plastic device.