I had a leak from the T connector to the upper radiator hose about 15 months ago. At the time I decided to try just an O-ring replacement. I bought the Dorman kit and also ordered the motorcraft because I wanted to compare. The Dorman and motorcraft looked and measured the same. I decided to also change the lower O-ring also to the lower inlet housing (OEM motorcraft to the upper radiator hose, Dorman to the thermostat housing). It's been about a year and the upper seal is fine, but...

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