Like any good repair, this one started with a flashlight and a vague idea of what might be wrong.
Found it! One of the hoses to the degas tank was broken.
We reused the coolant lines from the donor car, but after this we'd suggest starting fresh.
One way we tried to bleed the system: pressurizing it with a garden hose, then slamming the cap onto the radiator as quickly as possible. This didn't really help.
When we built the car, this fitting was capped–we figured the rear radiator cap on the degas tank would be sufficient. Apparently, it isn't.
We rigged up an overflow tank out of some scrap fuel line and a water bottle.
It's not pretty, but it works: the car now runs cool.
After breaking down in our last update, we dove right into our Factory Five 818 hoping to fix its cooling problem before its first autocross–which was now just days away.
After some quality time with a flashlight, we found the problem: a broken coolant hose that was nearly hidden by our degas tank. We replaced it with a hose from the local parts store, filled the car back up with water, and were met with… more overheating.
Hmm, that’s odd. We felt all the coolant lines, from the front of the car to the back of the car, and realized that though the engine was overheating, the radiator was cold. This meant that either our cooling system had air in it, or our water pump wasn’t working. We hoped it was the first scenario, and tried bleeding the system.
But, no matter what we tried, we couldn’t get warm water to make its way to the radiator. We took a step back, and looked the entire system over. A WRX’s cooling system is fairly complicated, and it only gets worse when it’s transferred to an 818. It has two radiator caps, one on the degas tank in the back and one on the radiator in the front. We noticed that the overflow fitting on the radiator was plugged during the build, and had an “ah-hah!” moment: If we plumbed the fitting to a coolant expansion tank, then the bubble in the radiator should disappear, and the car should fill itself with fresh coolant.
We rigged up an expansion tank with a water bottle and some scrap hose, and it worked great! We were finally ready to autocross.
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