2.5L Engine and Gasket Problems

[Gilles Gour]

I'm noticing that this thread isn't differentiating between specific model years or phase I or phase
II designations.

I just went out and took a look under the hood of my '02 OBS 2.5, and what I see is:

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1. The engine IS positioned at a slight upward attitude (front IS higher than the rear).

2. The highest point of the crossover tube IS the exit end (hose end).

3. The upper radiator hose IS positioned in a slight incline as it makes it's way to the upper tank
which visibly IS easily the highest point of my cooling system.

Essentially, my vehicle has a complete uphill path for air exit.

To top it off, when I purge/burp my cooling system, I have the front of the car up on ramps which
effectively doubles the incline of "air rise" out of the system. Yet during normal operation after
the system is closed back up, I still get a slow stream of air bubbles out of my overflow tube after
the engine reaches full operating temperature. The bubbles do not stop, they will continue week
after week, month after month.

I've been watching this phenomemon for 4 years now. Can anyone explain this?>

This steady stream of bubbles is regarded by many as a sign of an
internaly leaking head gasket (leak is between one of the cylinders and
coolant system. The fact that, in your case, this has been occuring for
years is sign either that it's not a leaking head gasket or that the
leak is minor and not expanding for the time being. Sure thing though,
air or gases are entering your cooling system somewhere.
Does the cold level of coolant in your overflow tank stable or does it
slowly rise day after day?

 

[Danny Russell]

This steady stream of bubbles is regarded by many as a sign of an
internaly leaking head gasket (leak is between one of the cylinders and
coolant system. The fact that, in your case, this has been occuring for
years is sign either that it's not a leaking head gasket or that the
leak is minor and not expanding for the time being. Sure thing though,
air or gases are entering your cooling system somewhere.

It's either that or there's a steady "slow-boil" happening, problem is I don't know which. It
drives me nuts not knowing. Coolant mix is 50/50, system builds pressure, and I've tried swapping
in a fresh rad-cap just for the hell of it, made no differance.

The intensity of the bubbles is related to how hard the engine gets pushed, meaning I can build more
bubbling by running at larger throttle openings, at higher RPM, on hotter days (all three
contribute).

Does the cold level of coolant in your overflow tank stable or does it
slowly rise day after day?

Other than the normal variance in level between a fully cold engine and a fully hot engine (couple
inches), the level stays steady. I've been getting a bit more black flakey stuff floating in the
overflow however.

 

[Carl 1 Lucky Texan]

At one time, didn't Subaru use a flow direction opposite of most other
vehicles? Does the coolant now return to the engine from the bottom of
the radiator? If not, it would seem quite easy for the coolant to 'gulp'
a bubble from any head space in the radiator and possibly pull it into
the engine. maybe the radiator could be 'cross plumbed' if it flows wrongly.

Carl
1 Lucky Texan

 

[Gilles Gour]

It's either that or there's a steady "slow-boil" happening, problem is I don't know which. It
drives me nuts not knowing. Coolant mix is 50/50, system builds pressure, and I've tried swapping
in a fresh rad-cap just for the hell of it, made no differance.

The intensity of the bubbles is related to how hard the engine gets pushed, meaning I can build more
bubbling by running at larger throttle openings, at higher RPM, on hotter days (all three
contribute).




Other than the normal variance in level between a fully cold engine and a fully hot engine (couple
inches), the level stays steady. I've been getting a bit more black flakey stuff floating in the
overflow however.

I have no first hand experience with blown head gaskets, but your
symptoms and specialy the «black flakey stuff floating in the overflow»
point to such a problem. Taking into account what I've read and heard
numerous times, I think you should have a mecanic test your coolant to
determine if exhaust gas is being pressure fed into your cooling system.
I think that if you replace gaskets early, it's just that, but if engine
overheats too much, this could mean warped or cracked heads or even block.
Good luck!

 

[Rick Courtright]

inches), the level stays steady. I've been getting a bit more black flakey stuff > floating in the overflow however.

Danny,

I'm with Gilles on the idea of having coolant tested for exhaust gases.
My EA-82 engine's had a slight seepage from the head gaskets for years,
and doesn't use a drop of coolant (to speak of!) during the summer, but
during the winter, when things get a chance to cool and contract, I have
to add coolant at least every week. I have to do a compression check to
be sure, but my first guess is the gasket's not fully blown, but things
aren't tight enough in the engine to keep it well sealed. But at 356k
miles, I suppose it's entitled to its oddities.

So you could have a tiny leak, not enough to cause major problems, but
it's still there.

Good luck!

Rick

 

[Danny Russell]

Gilles wrote:

I Have no first hand experience with blown head gaskets, but your
symptoms and specialy the «black flakey stuff floating in the overflow»
hint to such a problem. Taking into account what I've read and heard
numerous times, I think you should have a mecanic test your coolant to
determine if exhaust gas is being pressure fed into your cooling system.
I think that if you replace gaskets early, it's just that, but if engine
overheats too much, this could mean warped or cracked heads or even block.
good luck!


Rick wrote:

Danny,

I'm with Gilles on the idea of having coolant tested for exhaust gases.
My EA-82 engine's had a slight seepage from the head gaskets for years,
and doesn't use a drop of coolant (to speak of!) during the summer, but
during the winter, when things get a chance to cool and contract, I have
to add coolant at least every week. I have to do a compression check to
be sure, but my first guess is the gasket's not fully blown, but things
aren't tight enough in the engine to keep it well sealed. But at 356k
miles, I suppose it's entitled to its oddities.

So you could have a tiny leak, not enough to cause major problems, but
it's still there.

Good luck!

Rick

Thanks Gilles and Rick. I'm just delaying the inevitable. I purchased a second car ('00 OBS 2.2)
in preparation for dealing with it. The irony is that the 2.2 bubbles as well, no black flakes
though.