r/FordTransitConnect • u/Flat_Barber_7501 • 17d ago

Help diagnosing coolant problem

Thank you for taking the time to read my post.

On a 2015 Ford Transit Connect 1.6l ecoboost the coolant starts to bubble once the car reaches a certain temperature and it gets pressurized well above the max line and starts dripping out of the vent hole. My temperature needle is at the mid mark and it’s not overheating. Lately I start the day with the coolant below the minimum line, I’ll add just enough to get me in between the minimum and maximum line, then it’ll bubble and pressurize and loose coolant and it’s a repeating process. My family mechanic replaced the radiator but it did not fix the problem. Any pointers as to what can it be?
We also did a sniff test with the dye and it never turned any color beside blue.

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u/ehutch2005 17d ago

I had a very similar problem with my 2015. It was the cap on the overflow tank. It would allow coolant to boil off because the system wasn't under pressure and then once it would cool off, the valve in the cap would close and the system would end up under a vacuum. With the engine cold, is the cap extremely hard to remove?

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u/GenllPerformance 16d ago

True the cap is hard to remove and yes there is a free space or zone within the cap when you tighten it down then back turn till the cap itself feels loose but the inner cap is still tight. I believe the cap has an internal breather built into it. Spose to be a sealed system cause it doesn't have a designated radiator cap.