Spent a whole day chasing a phantom coolant leak on a 2012 Focus

Got this car in last week, customer said it was losing coolant but no puddle. Pressure test held fine, no smoke, nothing. I'm checking the usual spots for hours, the water pump, thermostat housing, heater core lines. Finally, after like six hours of looking, I spot a tiny, slow seep from the plastic seam on the coolant reservoir itself, but only when the engine was hot and the system was under full pressure. The plastic had a hairline crack you couldn't even feel. New tank was $45 and took ten minutes to swap. Ever have one of those jobs where the fix is simple but finding the problem eats your whole afternoon?

2 comments

2 Comments

casey_ward512mo ago

Used to think those plastic coolant tanks were basically just fancy jugs and never the real problem. Had a Civic a few years back with the same mystery coolant loss, no drips, nothing. I was sure it was the head gasket starting to go. Spent a whole afternoon looking everywhere else before I finally saw the tiniest bit of steam coming off the tank's neck when it was hot. Swapped it and the level never moved again. Now it's one of the first things I check on those older cars, those plastic seams just get brittle and give up.

grace4192mo ago

Totally feel this, had the exact same panic with my old Corolla. Watched the coolant level drop for weeks and was convinced it was something major. Finally caught a tiny crack near the top hose nipple when the engine was fully hot, just a faint wet line. Threw a new tank in and it's been solid for two years now. Those plastic parts just don't last forever.