Subaru's heater is very difficult to get all the air out of, so CHECK your coolant level straight away, if you are losing coolant, the heater is the first part you notice it in, I have known this noise on Legacy's that have taken weeks to bleed the air out of the system, the noise is exactly as you describe, its water flowing from one side of the heater matrix to the other.
Check your coolant level now in case you cook your engine!!!!!!!
Checked my coolant level - as usual I could see a thick blue colour liquid in the bottom inch of the translucent filler pipe so I thought it was OK.
To make sure I started pouring in water, and kept pouring and pouring, tipped in some neat anti-freeze then some more water. After a total of 1 litre of liquid the stuff was finally nera the top of the filler pipe. So, yes my coolant was rather low. Thanks! I've never had a car where the coolant level was SO difficult to gauge, am I doing something wrong?
I'm surprised my coolant temp gauge has been reading in the normal central zone considering the level. Any comments?
Pete, do you think I still need to replace the power steering fluid now I've filled up with coolant? Have you traced this trickling sound before to bubbles in the power steering fluid?
Silly question, I know, but where did the coolant go? As in: how does the system lose the coolant, isn't it totally sealed? Are some of the hoses slightly porous or is it gaskets etc leaking over time?
To recap, last night I added 1 litre and went for a run.
Then this morning before going to work I checked the level and poured in some neat antifreeze (yesterday's fill was a bit more water than antifreeze). I only had about 300ml left and poured all that in and still it wasn't registering on the filler. I'm pretty sure I heard the 'trickling water' sound on the way to work.
At lunchtime I bought another bottle of anti-freeze and added about 800ml MORE down the filler, took the car for a 10 minute run and after that the level was OK (with car still hot). I will check it again tonight/tomorrow morning to see if I lost some more on my drive home!
Note that since I've been misreading the coolant level for ages, it hasn't been filled since my 30k service which was 3,500 miles ago. Still, that's 2 litres poured in out of a total capacity of 7.2 litres.
Firefox: I assumed the pipe from the top of filler pipe that goes into the wing was an overflow pipe that dumps excess coolant onto the ground. The pipe from the bottom of the filler goes straight across the top of the radiator into the header tank, so what do you reckon is in the wing?