When coolant goes out but air comes in..

After another occasion where the heat gauge jumped around like it was at a House of Pain party, I finally booked the Slowbaru for a full cooling system check. The good news is: It’s not the head gaskets. And even more amusingly, somehow the radiator lasted well beyond its typical life cycle..


Sometimes you’d go for a long drive and nothing would happen. Sometimes you’d pull into a town to fill up or grab some lunch after a long drive and the heat gauge would go up and up and up, like it was giving you one hell of an unwanted salute. Sometimes if you idled for too long the gauge would get angry, but not all the time (which caused quite a lot of confusion).

And so along the way I burped and filled, swapped out thermostats and caps and burped some more until finally after a recent camping trip, the gauge went up and my patience crashed down. No more of my own troubleshooting, enough is enough. So off to Natrad it went where it was pressurised, analysed and a couple of issues made themselves pretty clear soon enough.


I’d originally passed over the coolant stains on parts of the radiator as spillage, especially from the overflow bottle which would occasionally actually overflow depending on conditions. But no, turns out the stains were actually tiny cracks that were not only spraying coolant out (and continuing to stain everything) but also sucking air back in which was the last thing the system needed. The air would create bubbles, the bubbles would block things up along the path, the coolant temp sensor wouldn’t have anything to test for a few moments even with fluid still in the engine and the gauge would freak out on the spot. The system that was supposed to be holding pressure wasn’t which would also explain why the overflow tank was filling but not draining as quickly as it filled up.

leaking Subaru ej25 radiator crack 2005 subaru radiator
Ahh, there’s the issue..

Interestingly though the guy at Natrad told me that most radiators have a lifespan of about 10 years or so. Since mine hasn’t been changed since it exited the showroom floor, that’s 17 years it’s been cooling things down now, no wonder the old radiator was getting tired…

…along with the upper and lower hoses. Apparently they were on the way out too so new ones have been ordered. At least I know my thermostat is good..


While the air conditioning cooling system works, it actually works at 2 degrees higher than it should which means it was also putting additional strain on an already knackered system. However re-gassing this should get it back to regular operating temps. So come Monday it’ll be new rad, new hoses, new clamps, new gas, more testing. And hopefully after all that, we’ll have a healthy Slowbaru ready to roam the freeways again! Update coming to this post shortly – Wish me luck!



Well s–t. It’s the head gasket. Update coming soon but long story short once the radiator got fixed, it revealed where some of deeper problems were coming from..

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