I had been experiencing a coolant leak for over a year now on the Evo. The coolant level on the overflow tank would drop, and sometimes I would spot drops of coolant pooling on the top of the transmission or transfer case. This didn’t immediately begin after the motor build, so I figured there was something with one of the hoses or a seal. I had several shops, including very prominent “Evo” shops take a look, several times, only to tell me that they did not see any leak. I always referred to it as a “leak” but I wasn’t sure if it was leaking, burning, or what it could have been.

I measure the coolant the same way every time – I park in the same spot in the garage, have a line on the coolant overflow tank (slightly lower than the full line, to compensate for how much the coolant can rise during autox/track), and measure cold-for-cold. While I was experiencing this leak, the coolant in the overflow tank would slowly decrease after each drive. Both evo shops dismissed it, though the second time there was extensive reworking of the hoses in the back, which can rip and cause leaks from time to time. I asked them to drive the evo to witness the decrease, but was told they could not do something like that (presumably, a waste of time). We had run pressure tests, but the leak was not evident from them. This told me the leak was something related to a hot/cold cycle.

I finally took the evo to a local St. Louis shop, Ecotech, (a Subaru/WRX/STI shop) and they were fairly certain the leak was coming from the back of the head/head gasket. I had been figuring there was an issue with the head gasket, given every other avenue of the leak was explored. What the shop found was even more surprising – the head studs on cylinders 3 and 4 were loose. Given the head hasn’t been off the car since the car had been rebuilt, that only left the builder of the motor to blame. Same builder that removed the balance shafts without asking when he built the motor, and the same builder that left me with an oil leak after not properly sealing the oil pan. Outrageous. It’s really a wonder there wasn’t any actual damage to anything from this. At this point, not even going to bother going back or mentioning this to either of the shops that had been working on the evo since. It’s not worth it, and I likely wouldn’t get anything out of it anyway.

Ecotech put everything back together, machined/polished the head, and replaced all the gaskets and seals. One interesting thing – I ordered new ARP headstuds – standard 1000’s or whatever, and the shop said the headstuds I had in the car (ARP 625+) were so good that they preferred to reuse them rather than use the ones I bought. I looked it up, and sure enough the 625s are fine to reuse, so we went with it. I also had a new OEM thermostat, so the thermostat has been replaced as well.

I’ve been driving the evo around here and there, and completed a road trip over the weekend, while carefully monitoring. I am fairly certain the coolant leak is finally finished, though I am still carefully monitoring for this to settle down. Of course, now, I have an oil leak, obviously related to the work done to the car.