Yowie wrote:As far as I know it's the original standard radiator. I bought the car at 139,000km. Now at 183,000. Never a problem per se, but the IAM is terrible and it seems to run around 95-96 water temp, and wondering if that is making it ping? I run it on 98, but even with octane booster it still isn't very happy. Wondering if ( hoping ) lower temps will reduce / stop the pinging ( if that is actually what is causing the problem ) and consequently stop the ECU from pulling all the timing out of it and making it feel like a NA 1300?
Do you still have stock headers on your 3 litre? There is a Skid Factory video where Turbo Yoda / Alan comments to the effect that the stock headers (designed to heat cats for emissions) cause a lot of pinging.
In terms of your main question - in theory lower coolant temps should give you more headroom before knock sets in.
So my hand was forced a couple of months ago, when the one of the top radiator hoses had a pinhole in it. So while I had the radiator drained to chase the hoses, I took the opportunity to change the thermostat. I got the AA230 one, the 91 degree unit. I bought 2x 5L of the long life green ( not the ultra long life blue ) coolant from the local Subaru stealership, and bled the system according to posts on various forums. Didn't have any trouble, not like it has been made out to be. Sure it took a bit of time, but that was it.
With the new thermostat, it's made quite a difference to the engine. Now the car runs around 91 degree on suburban roads, 89 degrees on the motorway, and I haven't seen it get over 95. It used to run normally at 96-97, 95 on the motorway ,and I have seen it at 102 in summer. So it's running much cooler now, and the engine obviously appreciates it as the IAM is now sitting at 0.531. Still not where it should be, but much improved.
I have the radiator flushed and refilled in NZ before I brought the car over to OZ, and I used to hear the odd gurgle from the dash / firewall area at various times. It was not a Subaru shop, but a very reputable independent shop who I've had dealings with over a long period. Since I replaced the top hoses and refilled and bled the system myself, no more gurgles. So I'm thinking it wasn't bled properly the last time, and maybe that is why I think it's got a blown left hand head gasket. You can't tell to drive it, but it leaks oil that it never used to from I think the rocker cover, and around the head gasket area. I'm just going to keep running it while it's still going, hopefully it'll keep going for a while until I can round up all the bits for a Commodore LS and 6 speed auto swap.