Leaking coolant after thermostat change - Diesel Forum - TheDieselStop.com
6.0L Power Stroke Engine and Drivetrain Discussion of the 6.0L Power Stroke diesel engine and drivetrain in the 2003-Up Super Duties and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 6.0L Power Stroke engine.

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post #1 of 1 (permalink) Old 08-14-2019, 08:18 AM Thread Starter
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Leaking coolant after thermostat change

Wanted to post this to pay it forward. I just changed out my thermostat and suddenly found that I had a pretty significant coolant leak under the motor. I first took off the new thermostat, inspected everything and then reinstalled it. Same thing happened. Big leak of coolant under the motor. I looked at the thermostat housing, as best as I could with all air box in the way, and couldn't see a leak from it anywhere. Then I read that others had the same problem and started to look at their water pump for a leak. That just didn't make any sense to me. I didn't have a leak before the new thermostat install, so the likelihood that all of a sudden the water pump developed a leak seemed very remote.

Finally I decided to remove the air box to get as good a look as possible at the thermo housing and I saw that the leak was coming from above the housing, meaning it was coming from the large radiator hose at the connection to the thermostat. I removed the hose, purchased a new hose just to be safe, reinstalled everything and it is not leaking anymore.

I don't think there was anything really wrong with my old hose but if you don't get the spring clamp in the exact same position as where it was originally, the coolant will leak down the downhill side of the hose at the thermostat connection. It's very hard to see. The original hose has a very defined indentation from the spring clamp being on there for 12+ years. That's why I decided to just get a new hose and be done with it.

Hope this helps others. Don't believe the water pump hype. It's the hose!
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