Knocks and burps – sorting out the Subaru one week in

Sigh. I was going to do a big write up about my latest acquisition, a 2005 Subaru Impreza aka Bax the Boxer here. And eventually I’ll get to writing up how I’m enjoying it, although wishing it had a couple more features like a sunroof and better fuel range info. But first things first, a week into owning it and wouldn’t you know it? I’m already looking up replacement parts..

Now before anything, let’s set the record straight – Bax has been very well looked after by the original owner. The head gasket that goes bad on these early Subis? Performed 80k ago by a proper garage complete with receipt. There’s a folder full of service history coming, this car has been well looked after and service and it shows. Unfortunately sometimes things just break and unluckily for me it’s been within the first week of ownership.
I could whinge and moan but I’d rather roll up the sleeves and get tooling instead, so let’s do that.


For some reason my OBDII scanner likes to connect to my phone but refuses to shake hands with the ECU (actually the reason is Subaru’s special SSL – Subaru Select Monitor. Basically unless your adaptor has this mode which mine doesn’t, it means you’re SOL)

Luckily it’s dead easy to get it into diagnostic mode with this car and you don’t even need a paperclip!


  1. With the engine off, find the two black connectors under the dash (they may be tucked away) and connect them up.

  2. Turn the key to on but don’t start the car.

  3. Look at the check engine light and count the flashes. If there’s an issue, you’ll get a combination of short and long flashes.

Eg two long flashes and two short flashes on repeat would be error code 22.

Two long flashes, two short flashes, three long flashes and one short repeating would be error code 22 AND error code 31 etc.

  1. Write them down, turn key off, disconnect the black plugs, deal with your new issues.


So far it’s the only code that’s popped up and a quick Google and read up on various forums suggests it’s the engine knock sensor having a rough time. This would possibly explain the higher than usual fuel consumption at the moment. It’s easy to find, on this model it’s under the throttle bodies, passenger side.

Yeah that crack isn’t a great sign at all. A direct replacement from Subaru is around $220, a non genuine from Repco about half that. So I’ve ordered one in and will swap it out when it arrives.

While I wait for that, onto the next issue!


Bax may have been sitting for a while before sale and I’m saying that because the tires needed a fair bit of air and he seemed a little slow on the uptake (possibly due to the knock sensor failing and playing things carefully) until I reset the ECU. After a fang on the freeway though, I notice the temp gauge hit nuclear and so I quickly pulled over and let him cool.

At first I thought I’d sprung a leak in the cooling somewhere judging by the green stuff all over one side of the bay but since the reservoir tank was boiling away and apart from the fluid in the bay, nothing else was dripping out onto the ground. Something had possibly blocked the flow somewhere, the stuff in the reservoir boiled and expanded and forced itself out the top where the hose to the radiator emerges.

After the cool down though? No problems. He made it home fine and has been working well ever since. So just a random thing though? Possibly, but my money is on an air pocket somewhere in the lines. And this thought became more apparent the more I read about it.

Apparently a common sign of this is the sound of something sloshing around in your engine bay when you drive from a cold start and what you’re hearing is the air bubbles in the system hanging around your heater core, directly behind your dash. Normally not much of an issue but it seemed to be for me so it was time to get them out.


This is not a particularly big job but it’s not a quick one either. Because you’re working with coolant that will heat up, you will need gloves and because of the chance of mess, you will need rags too. Give yourself at least an hour for this.

-Jack up the front of your car. You’ll want your radiator to be the highest point of your cooling system. This also allows you better access under the front to check for possible leaks, learn where your oil filter is and see how clean or filthy things are at the bottom. The jack stands I bought for the Stagea turbo install finally see light of day again, joy!

-Take the cap off the radiator. You can do this process with a special funnel but it works without one too. Just be aware that things will get messy without it.

If radiator levels and overflow tank levels are low, top them up.

-Start the car with the heater set to the highest temp, fans on Max. This will help cycle things through. It will also take a long time to get to operating temp (about 30 mins or so) but that’s okay because we want to give the air pockets and bubbles as much time to escape out of the open cap.

burp Ej25
There goes one now!

-Watch for bubbles popping out of the radiator. This is a good sign, better out than in. Occasionally squeeze the upper radiator hose to help it along.

-The coolant level will rise and fall over time as it goes through a few cycles, that’s completely normal. As is the timing of the bubbles. I had a lot at the start of things and a few when it finally hit operating temp (once it’s halfway up the heat gauge you can turn the heater off) but about 10 minutes later they ceased and this is what you’re looking for. When there’s no more bubbles to be seen, switch the car off and let it cool, topping up again if need be. This is a good time to clean up any spills, pack up your tools and get ready to take it for a spin to check things out.



Well completely unrelated to the cooling, my front passenger tire looked a little low and a quick blurt to the nearest servo with air pump confirmed it. Down to 9psi instead of 32 where it should have been. Another random issue already? Seriously? But it’s got air now and I’ll keep an eye on things across the day to see what it’s doing.

The temp gauge behaved itself just fine, sitting right where it should. Even better, I didn’t hear a sloshing noise. It looks like it’s been properly burped and cleared of air pockets now which is brilliant and hopefully the end of the overheating issue. Although when I checked the bay again after getting home, there’s more coolant everywhere and the overflow tank has too much in it.  Turns out I overfilled it, it heated up and with nowhere to go again, it spurted out the top again. It’s not going to blow things up, more make even more mess.
Well that’s another lesson learned then – don’t have too much in there. You can either remove the excess out of there when it’s cool with a hand pump or a turkey baster or unbolt the reservoir and pour out what you don’t need.

Next post – Knock knock, you’re not working, get out. Stay tuned!

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