Bit of a late response, but as it turns out they then replaced the radiator as well, making that 2 new caps, 1 thermostat, 1 radiator and the main fan relay (only has one). Only thing that hasn't been replaced on the front now is the fans and their control box, both of which are fully functional.
They took it for multiple test drives down the local highway, and it came back "fine", though I doubt they actually popped the hood and checked it...
Convinced me that it was good to go, had not got any official testing documentation yet, but I basically decided to go up there and check myself, as at this point they couldn't seem to see the issue. Sure enough...
Got in the car, started up, it was already at optimal temp (they tested it just an hour beforehand)...
and immediately I noticed a 'ticking' on the steering wheel... "oh this is going to be a fun, short trip.
Decided to ingnore it for now, drove it out the driveway and proceeded up the hill to the main road, watching the temp guage, get to a little bit of traffic before the intersection...
Guage was 1mm above the normal spot... 2mm... 5mm... aaaand zoom to redline... coolant was
everywhere...
Ok, joking about the coolant part, but it definitely was bubbling with the overflow at its peak. Parked it just on the side and went back down to the shop, guy came to look at it and after a bit of demonstration with stall-throttling it, sure enough the overflow was spewing with gas way more than it ever had before.
So in summary they've booked another engine replacement first thing in january, so we should hopefully be out of this scenario pretty soon. The fact that I could feel a ticking motion in the wheel was quite surprising though, prior to it being sent back, and with the older engine as well, the worst I got was a general engine rumble similar to a straight-4. But in this case there was a little rumble, but with an additional little thud that ran in exact timing with one of the cylinders. Seems as if the test trips were just enough to pop that one cylinder just enough to compromise the engine completely...
Hopefully they actually go through the effort of testing the next engine properly, not that it's any extra cost to me other than wasted time...
jeb wrote:Maybe as a last ditch effort before warranty call, could install new radiator, upper and lower hoses & set of screw type hose clamps. Even though pressure test held up, perhaps the radiators plastic end tanks could suck air into the system?
I'd say it's a warranty run, these engines have the water pump built internally behind the timing chains, so basically the only place gas can get in is the heads. Air could come in via the radiator ends and hoses, but only when its all cooling down, and only if you had a bad cap really. You should notice cooling loss on said areas before I think it would be bad enough to suck air, but also the hoses would likely collapse in the process (ie a cap not resetting to neutral when the pressure drops).
There's these cheap radiator funnels you can get, I think I got mine from supercheap, where you basically just shove it into the cap hole, top it up if necessary, and start and bleed the engine of any extra air. Having it on an incline helps, set the heater to maximum heat and fan speed and squeeze the top hoses every so often, if the engine's not blown you shouldn't get any bubbles or rising coolant after it heats up. Last I checked the thermostat is supposed to open for an optimal temp around 70-80C, which is not nearly high enough to boil the coolant.
If there's some regular bubbles, or even some little tiny 'foam' bubbles coming up, give the engine a rev and see if even more come out. If they do then a head has been compromised.
For automatic trans cars, you can do an extra trick that I mentioned above, where you basically put it in reverse (or drive on an incline), hold the brake pedal hard as well as keeping the handbrake on, and rev it up. Rev it slowly in the off-chance it starts to spin a wheel, but at least in the outback ECU it hard-limits the RPM to 2K, no higher. The accelerator basically dead-zones at 2K because the ECU knows the car isn't moving.
Reason being is the H6 is very resistant to leaking at the heads under low power, as each cylinder is at a much lower power to that of the H4's. The above stall stress, or simply flooring it on the road, brings the pressure up and reveals the leak.
edit; here's actually a video I took of the engine prior to it being sent back, you can see how it's bubbling (and also spewed quite a bit of coolant out the funnel), while running pretty rough on idle;
https://1drv.ms/v/s!AvmNywYaxo2RnURisNso0m1pVO-D(oh and sorry about the video orientation, my phone's gyro is bust so it doesn't know to rotate the video when recording...)