Bit_the_Bullitt
Well-Known Member
The new/updated I put in starts to open at 195, I verified by boiling it.What's interesting is the strange variance on temp specs of the same part number. Supposedly the Motorcraft RT1258 is correct for the 5.0 engine, but I've seen lots of places list it as 180 degree, yet on Fordparts its 190. The aftermarket ones seem equally confused, with 180 being listed as "OE temp".
This really seems like a slight engineering change was made, possibly a higher base temp, but more flow over the full opening range?
It also has 90.6C stamped/etched on it, which is 195.08F.
The Motorad one (right) looks like a cheap piece of crap for $11 from Autozone and it seems like a 170F one. It has "Motorad 1021" on it, I don't care if it technically starts opening sooner (clearly it was insufficient), haven't tested it yet. All I know is it's running better with Motorcraft.
Yeah, the truck had orange. I did a chemical flush (Motorcraft VC-1, made for aluminum rads) and added the new yellow coolant. I did not notice any scaling or gunk come out during the flush, but that could also mean it's settled at the bottom of the rad or dissolved in the chemical flush.Its therorised that when you open the cooling system, the old orange coolant becomes sticky when the thermostat is exposed to atmosphere. I'm not sure thats the case, but I know the OEM one will stick if you open the system and don't replace it with a new OEM thermostat.
My Mustang has the orange/pinkish one.
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