I like my subaru but head gasket have used the sealant no problem yet

187,000 when the gasket let go. Repaired by independent local shop, now have 212,000 with no further problems.

Here is some very interesting info on how to fix the problem yourself:

Yah....did anyone ever figure out wtf a "swirlpot" is?

Not being a mechanic...does anyone have a photo of this?

-John O

The theory behind that is that air gets trapped at the highest point of the cooling system inside the engine and that getting rid of that air will eliminate a possible local coolant boil that - through its expanding gas bubble - blocks the heat transfer. This in turn accelerates the phenomenon and the engine overheats, may even warp and blow its gaskets.

In this theory, blown gaskets are the consequence not the cause of the issue. This may be possible, since many many 2.5 engines of identical design do NOT blow their gaskets - they may just have been properly bled of air inside the cooling system.

My concern with the solution posted is, that by connecting a pipe into the coolant flow inside the engine, you disturb the flow surface and create a potential nucleus for cavitation. This may cause the exact problem the device is supposed to eliminate. IMO, It would be a good idea to first examine the rate at which the coolant flows in that area.

florian /FFF/

This is an odd question, and is prompted by one reference I read on the 'net - I know dangerous - but that is why I'm asking. Is it true that Subaru at one time or at present routes coolant INTO the radiator at the bottom and OUT to the engine from the top? If this were true it seems it would be a source for air getting 'gulped' into the coolant system.

Carl

1 Lucky Texan

Florian Feuser /FFF/ wrote:

If this is what I think it is it's the coolant expansion tank in modern coolant systems.

Old sealed systems had an expansion tank built into the end caps, and you filled directly through a cap in the radiator.

Later systems have a few hoses and a bottle with a cap, this is the high point of the coolant system and is likely what the guy is calling a 'swirlpot'.

Since all the coolant passes though the expansion tank it is likely the bubbles will eventually get passed out and remove themselves from the block.

From my experiences with VW inline motors there is a real concern when refilling the motor to avoid bubbles in the block and refilling via the 'top' coolant hose is key. It's also called backfilling.

If what the link mentions is true then getting all the trapped air out is key, and keeping any that gets in from remaining is beneficial.

TBerk

I found out a 'swirl tank' is not exactly the same as an expansion tank.

It has an intake and an outlet where the coolant flows into a (cylindrical?) tank before going on to other, more common parts of the system like expansion tank, radiator, and/or overflow catch bottle.

It enters at an angle, causing the 'swirl'.

Now, what possible reason you would want one still remains a mystery to me, but Google will find a few links if it's really interesting to explore further.

TBerk