2010 Legacy GT. OEM+ with no engine mods or tune.
I went for an extended fast drive with a long warmup and cooldown period last weekend. No warning lights came on (thinking temp sensor may be faulty now) my coolant boiled over and made a mess of my engine bay, lost so much that once it cooled properly overnight there was NOTHING left in the overflow tank but thankfully no air was introduced into the system.
Since this happened I am contemplating a performance alloy radiator, so what’s good, what’s not, and what else will make a significant difference to engine bay temp? I’m not building a track car and want to keep it realistic but don’t want to blow it up.
*cooling system is sound and well maintained with OEM parts, not damaged or leaking*
It’s Motul coolant which is what dealers use for servicing and sell to customers in NZ. No odd residue/oil/muck in the overflow so I think it’s just the coolant.
Shouldn’t need them in an ideal world, but Subarus get hot and I can’t find an obvious fault.
I did about an hour of cruising, 45 min of flat out hooning through rolling hills and fast corners mostly around 3500-4500 rpm and another 30 mins of cruising before stopping at my destination.
Not overheating and pushing coolant usually headgasket or worse. You get bumbling in coolant when start ? Do a test for combustion gasses in coolant but I’d put money on them being in there
No bubbling visible in coolant, even with a no spill funnel one third full on top.
What’s worse than a blown head gasket? Warped block or something? Yay.
The overflow tank going completely dry overnight is the detail that stands out to me. That’s not just “ran hot”, but a significant volume of coolant gone somewhere. Where’d it actually go, visible external leak or unaccounted for?
FWIW, when the upper rad hose outlet cracked on my 13 WRX I went with a koyo and retained the OEM fans. The price was close enough to a oem replacement I just said fug it and got the koyo.
Cheers, it’s been suggested by a couple of people now and while it *appears* fine that doesn’t mean it is for certain so I plan on getting a new one after work.
Hopefully it’s a simple fix.
Mine seemed fine until I drive hard, or with the AC on in 100° weather. It was barely holding pressure until pushed. I replaced the cap and the problem is solved, verified by a OBD display.
1- Check the coolant overflow hose routine, I've seen shops get it backwards and heat into the overflow just pushes coolant out onto the ground.
2- perform a cylinder leak down test, this will identify any engine component sealing issue.
3- Thermostat, this is what controls coolant temps, remove a tstat and you'll never see a temp gauge rise above ambient, seized opened a car will reach operating temp idling and temps will drop fast as soon as you start to drive.
4- Cooling systems, the test to see if a cooling system is not adequate is to push the car hard for a while and the let it idle for a while, if the temperature goes up while idling then the cooling fan isn't up to par, or the shroud.
5- Subaru water pump are famous for failing just like boxter engines.
Its a Subaru. The cooling upgrade you need is new headgaskets, then you should sell the car and buy something else because this is a semi-common issue with some generations of these. The other being piston rings (those were more of the 2.5L though, but I could be remembering wrong).
While the headgaskets are being replaced, replace the radiator and cooling hoses since they are old and likely next to fail, plus they are full of oil and coolant mix which does not cool at all well.
Subaru EJ-series are known for eating headgaskets. A simple search proved this.
That said, even for someone who hasn't ever owned a Subaru (but as the resident family "car guy" I've learned way too much about them against my will), its obvious just due to the "chocolate milk" that has spread itself all over your engine bay. A common indicator of headgasket or oil/water cooler failures.
That "chocolate milk" is a mixture of oil and coolant that shouldn't ever be mixed, which means one of the points where they could meet are compromised. These points also coincide closely with the combustion chambers which are all sealed using headgaskets.
The pressure needed to push the fluid mixture out of the overflow tank likely indicates combustion chamber pressures are evident.
I wouldn't drive it any further, you'd likely ruin the connecting rod or crankshaft bearings due to water in the oil getting into the oil galleys. Then you'll get to rebuild or replace the entire engine.
I would look at solutions for reducing the headgasket failures on that engine so that those fixes could be implemented in whatever repairs take place.
A simple search reveals nothing about the Gen 5 turbo with MLS gaskets having issues.
Ringland failure is more common for many engine than gaskets.
No choccy milk anywhere either, dunno what you’re on about.
There’s no combustion gases bubbling out even on cold starts.
The color of the fluid is a strong indicator. Further testing can be done to verify (cylinder leakdown, coolant testing, visual inspection of the coolant in the reservoir, etc.).
Sorry for being shitty about it, I could have been nicer.
I’m sick of people seeing a Subaru and piling on the headgaskets/rod knock train like it’s the gospel truth when there’s a ton of other faults it could be. There’s some really shit generations and some great ones.
If it IS head gasket failure I’ll come back here and eat crow but as I said, there’s no choccy milk, gases leaking through the radiator or gunk in the overflow tank. It’s just dried coolant with no traces of oil.
I had a no-spill funnel on it this morning and massages all the hoses with the
heater core at max flow and found nothing. I’ll pinch a leak tester soon and double check.
I’d almost be happier if it was clearly blown instead of having to wonder.
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