Thanks rob, and indeed to Ed-EG, much appreciated info.

Last time this happened in February, when cold both the expansion tank nearest the turbo and the rad were completely full.

I took the caps off and there wasn't a drop missing.

Will try later though, remove both caps and see if they show a drop in level and black scum.

 

Yes, around an inch - perhaps less is missing from the top header tank. Although the missing water is still only the neck part of the tank, so not very much at all.

No black scum though, nor under the radiator cap - this was full to the brim by the way.

When undoing the header tank cap, I heard a bit of bubbling for a few seconds, and also from maybe the overflow tank / radiator area.

Best to top up the missing small amount in the header tank?

 

To have all this surplus coolant, is there a chance that at some point my coolant system has been overfilled? If so, how?

I have almost a litre of it out the system sitting on my shelf, but is there an air pocket somewhere do you think that would be the same size as a litre of coolant if you see what I mean?

 

Nearly a litre? I'm definitely thinking you have an airlock, or gasket failure. If you look at the size of the reservoirs it would be hard to over fill the system by a litre! Have you tried burping it yet?

 

No I haven't yet, don't think I've got the bottle to do it in fear of making things worse.

When and where would I add the coolant if the levels drop? Into the main header tank by the turbo?

I'd then be adding cold water to a hot engine?

 

I haven't read all of this thread and I don't want to be alarmist but:- I would not run your car on boost until you get it to an expert and establish just what is going on.
If the Head Gasket is starting to fail just pushing water is nothing but if the water goes the other way into the combustion chamber you run the risk of hydraualic compression, i.e. water does not compress and that can take out your engine, and I mean piston, conrod and crank in whatever cylinders are affected. This from experience,so be careful.
Trev

 

I am going to be very careful.

If I had an airlock (fingers crossed) causing this rise in coolant, how does it push the water out and into the oveflow tank?

Also, if an airlock causes this (I'm not saying it doesn't) but how come the air doesn't follow the coolant into the overflow tank and "self burp"?

Again, if I had a large void of water, am I right in thinking that when everything cools that when the levels drop, it would self syphon any coolant it needed from the overflow tank, or is the overflow tank a one way thing if you see what I mean?

 

Airlock is simply where air gets stuck in the coolant system at certain points such as turns in the pipework. As air will always float up through water, the power of the pump alone is not enough to force the air down through the piping, and hence it gets stuck.

With regards to the burping you cant really make the situation worse, you would add the coolant in to the top reservoir as this is the highest point of the coolant system, basically once you see the bubbles in the funnel you know the air is escaping and not getting drawn in somewhere else. You are right that you'd be adding cold coolant to a hot engine, but you'll be mixing it with the rest of the coolant at operating temperature, so I highly doubt you'll cause damage through it (unless youre keeping the coolant in the fridge? )

 

The symptoms appear to have been going on for quite a while which if the HG is the cause in my view brings you closer to an engine catastrophe.
In a healthy car the coolant in the overflow bottle should move between low-level mark (cold) and high mark (hot) and be as regular as clockwork. If not, let someone who knows get to the bottom of the problem. The stakes are high with these performance cars.
Trev

 

Very tempted to now try this.

I would add the coolant very slowly into the side of the funnel.

The coolant temp at the moment is 35 degrees according to my PSi3.
That should be cool enough shouldn't it?

 

That should be fine, bear in mind that this isn't a guaranteed fix, but it certainly helps get the air out.

Of course, if you do have head gasket failure, the symptoms will repeat themselves and then you can be sure it isn't just airlock.

 

Ok, say if I perform the burp this evening, do I leave the header tank cap off whilst waiting for everything to cool down / drop down?

Then add coolant into the header tank if needed and into the rad if needed right?

Seems like the rad cap stays on throughout the process until checking the level once it's all cooled down?

Will I also be able to clearly see a water shortage in the header tank whilst it's running when looking down the funnel?

 

only take off the cap for the top reservoir, leave the rad cap on throughout the whole thing. You'll see the water level drop from the top reservoir as this is the highest point in the coolant system, so just add a bit at a time through the funnel thats jammed in to the opening in the top reservoir.

When it's cooling you'll need to leave the top cap off as the funnel will still be in (see the video) once the coolant has cooled down to ambient temperature you should be able to take out the funnel without making too much of a spillage.

 

Ok cool.

 

Glad to help mate! It's easy enough to do and the process is pretty much the same for all cars, I found watching a few videos of it on youtube made it easier to figure out when I first did it.

 

Ok burp done. Just waiting for it to all cool right down and will then see where the levels are at.

At first there were quite a few bubbles that I could see before the coolant level started to rise into the funnel. Not huge bubbles, but quite a few of them

Once the level started rising, there were quite a few tiny bubbles appearing. These got bigger as I gently squeezed the S bend top hose of the rad.

After 4 or 5 cycles of the cooling fan coming in and the water dropping and rising (the lowest it dropped was to the neck of the header tank) I stopped in fear or anything over heating.

There were still bubbles coming out, but I don't think as many.

So, burp or part burp now done, and thank you for the step by step guide.

I didn't need to add any coolant at any stage.

Will see now how levels look once cold again - this will be a good few hours this time of year of course.

I noticed that the rags / microfibre cloths I used around the base of the funnel did get damp, but not soaking wet.
I poked the rags in gently with a small screwdriver to wedge the funnel as steady as I could yet not damage the header tank neck.

For the record, when cold, as I opened the header tank cap, the overflow bottle bubbled and the level rose roughly a centimetre.

Fingers crossed, hope I've done it right. There wasn't huge amounts of air, but perhaps I will have another go earlier in the day sometime.

But for now, I'm pleased I have got at least some air out.

I got the impression that the bubbles would never have stopped, but called it a day in the end. Like I say, when I stopped, the bubbles were still there, but I don't think quite as many.

At no point was there a massive burp, when just watching it or squeezing the S bend hose.

After the overflow bottle level rose by roughly a centimetre at the beginning before I started the engine, it's level didn't move.

 

If there were still bubbles it just means there's still air somewhere in the system, but I imagine you'll have got a lot of the air out through the burping.

When everything has cooled back down check the top reservoir, the radiator and the overflow tank and top them up as required, only thing to be careful of is not to pour in the extra coolant too fast, as doing so could end up trapping a bit more air.

All going well you should see a drop in coolant levels once everything has cooled down!

 

Coolant temp now at 47 degrees. Will wait another hour or so.

Water in header tank approx an inch from the top of the neck at the moment.

Will check rad once header tank is topped up and cap secured.
I've also drained out the overflow tank to about and inch above the MIN mark, and will monitor this over the coming days.

 

The header tank and radiator can be filled up to the brim, in fact I'd recommend doing so to eliminate the chances of sucking more air from the tank / radiator in to the pipework.

The overflow tank should be fine there, although maybe put a bit more than minimum in in case the pump draws some fluid out of that tank, again, just to reduce the risk of sucking more air in to the pipework.

 

All levels behaving......for now.....

 

Just to add that to help with the burping, when having the header tank cap off, keep the car running in fast idle (2,500-3,000 rpm).
You will see the level dropping when doing this at which point keep adding coolant until it is full again.

 

Ah, never tried that to be honest.

If I do it again, I'll set the throttle down a tad then.

 

This has all the hallmarks of what happened when my HGs started to lift (2006 Spec D).

Through regular burping and putting the overflowed coolant back into the system , I limped along for another 6 months before rebuilding the engine.
I found that using over 1 bar boost would make the problem worse.

I'd start saving your pennies and make sure that the system doesn't overheat.

The reason for the excessive coolant build-up is that the when cooling down, the large air pocket compresses and you lose the vacuum that is needed to draw the overflowed coolant back into the system.
If this happens enough time then the coolant tank overflows and the air pocket is large enough to cause overheating.

 

I agree!

 

Indeed, snet is littered with threads of similar faint hope

 

Is there anybody driving one of these things with the original HG still intact?

Found out that mine was replaced 18k ago under warranty. Did Subaru use the same type of gasket for the replacements?

 

I am but I bought the properly built engine the 2.0

 

Yup, the decent one the Japs kept for themselves.

 

I think my 2.5 came with pretty decent head gaskets as standard!

I think the OP has lifting HG also and will be heading for a rebuild.

 

The latest:

Whilst the level in the overflow tank seems to be behaving, I took out a sample from it.

I got a flexible clear plastic tube and sucked a bit out.
I now seem to have black bits in the coolant, along with what looks like white / off white bits. I took the sample right from the bottom of the overflow tank.

They aren't big, but they are sinkers not floaters, and quite a lot of them.

I assume I have standard triple steel layered head gaskets, but do they have a coating or something that may be making it's was into the coolant, or perhaps I have a perishing hose somewhere maybe?

I'm also still getting this trickling water sound when I first start the car, it's coming from the heater matrix area I think, behind the centre console somewhere.