2012 Ford Focus, 155K miles, it is leaking a decent amount of coolant when my partner drives it to work but doesn’t even leak a drop if I drive it to work. The mileage is the same but I don’t sit in traffic. Could the extra heat from sitting in traffic be opening up a pinhole sized leak in the coolant line?
Edit: Thanks to a tip from the comments when the heat is turned on it leaks. I should be able to bypass that line pretty easy.
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It’ll be primed but not pressurized. Some leaks, especially in older rubber hoses, only leak under pressure when the swelling of the hose opens the split.
I’ve only seen bypass valves that block off one of the two heater core hoses to prevent flow but not both. Same idea as a thermostat blocks only one side of your radiator to prevent flow. So even though coolant isn’t flowing, it is heating up and pressurizing. There may be vehicles out there with an unusual design that blocks both inlet and outlet hoses to the heater core. But this isnt one of them.
Not trying to argue, just trying to share some of my knowledge as a former Ford tech.
Huh, didn’t know that. Most of my wrenching has been done on older GM trucks and they used a vacuum actuated valve that cut the heater core out entirely by closing the loop under the hood, so coolant still flows by a shortened path. I’m just glad ops problem was found there. Thanks for the info!
Ya, op got it figured out thx to you that’s the important part. I just wanted to add a little clarity for the poor bastard that will come across this post after googling “Ford Focus coolant leak”.