I'll add this TDC not to take sides one way or the other but to offer what I have experienced in this arena.Originally Posted by TDCRacing
I had a MotorRad thermostat, 180* in my vehicle that was a fail safe design, that is to say it was designed to fail in the open position so as not to block off coolant flow.
Id say this happened about two years ago, in the middle of summer, Id have to check my maintenance records to pin down the date. Anyway, I was delivering an order to a customer that lived just off the main road, about two miles down a dirt/gravel road. I drove slower as one would on that kind of road, but I wasnt creeping along either.
I get there, drop off the stuff, visit for a few minutes (he orders A LOT of stuff) then take off the same way. I get back to the highway and as I go to get on the highway, I feel my car shudder a little, like it missed maybe.
I take off and gun it a little and notice it seemed rather spunky for it being as hot outside as it was. Im looking at my speed and I notice that my temp gauge is on the floor, reading as cool as it will.
Im just a couple miles from town and all the stop lights and such but maybe 7 or 8 miles from the parts store. The whole time my temp never got off the floor, car seemed like it wanted to stall, large (400 RPM or more) swings in idle speed, Im sure in response to the extra fuel going into the engine.
But I made it to the parts store, got a new thermostat. No clue whatsoever why the one failed, I never saw temps spike to a point it would warrant the thermostat failing in the open condition. Once it was opened temps never came off the lowest reading even in the stop and go traffic.
I got a new 180* fail save t-stat in there and all was well after that. Never had another incident like that and chocked it up to just a faulty t-stat.
