1992 7.3L IDI Thermostat Troubles--

[k.thed]

Our 1992 F350 7.3L IDI--

... has got thermostat problems, again. It's on its third thermostat in the past three years. Once a year it's been in the shop to have it replaced. I don't understand why they keep failing? On a side note, this truck only has 55,200 miles on it to date. It sits quite a bit of the time. It only gets driven for farm work, ie, feeding cattle, putting out hay, moving hay, general around the farm driving. I change the oil and filters twice a year, simply to change the fluids and filters. It doesn't accumulate 5,000 miles annually, obviously.

So my question is, to all the other IDI owners, does the amount of time this truck sits have something to do with the fact that the thermostat keeps failing? This is especially difficult in the winter when these things keeps failing because the old battle wagon is cold blooded enough as it is. Stupid thermostat goes out, and it won't warm up at all. I've stuffed empty feed sacks behind the brush guard to make a grill cover to try and lock in a little heat for it (redneck enginuity, I'm aware. If anyone knows of a decent grill cover kit for the OBS, feel free to pass me some info on that!)

I know Motorcraft thermostats are supposed to fail in the open position, which is what happens since it won't warm up. And I know its had Motorcraft parts used on it because this truck has been serviced at the same Ford dealership that sold it new since day 1.

Any input would be appreciated.

[FordGuy100]

I was going to tell you to only use motorcraft thermostats...but it sounds like you already are. I honestly dont know why they are failing on you. Are you using the factory water temp gauge to see how fast it warms up?

[k.thed]

Originally Posted by FordGuy100

I was going to tell you to only use motorcraft thermostats...but it sounds like you already are. I honestly dont know why they are failing on you. Are you using the factory water temp gauge to see how fast it warms up?

Yes I'm using the factory guage. I know it's not fool-proof, but I don't have a need to install a bunch of aftermarket guages to get more accurate readings on it. Temp guage never reads much over the 'C' and never gets into the 'NORMAL' range. The heater blows... mehh... slightly warmed air. Even if I keep it plugged in, it still only ever rises to the 'C'. When I've gotten the thermostat changed, it would then rise up to the lower side of the Normal range when being driven. But I'm afraid the dang thing is out again.

Got your PM- I'll check that out! Thanks!

[FordGuy100]

I hear you on not wanting to throw money at it. But the factory ford gauges suck. Example, your oil pressure gauge will read roughly the same when your engine is producing anything more than 7psi. Now if its making less than 7psi oil pressure, it wont register anything. Kinda nice....

[k.thed]

Understandable. I know the idiot guages are just for show, but I figure the temp guage must be fairly accurate because when it's reading cold after running for an hour and the heater still isn't cranking anything warm out, something must be up lol. I had the dealersip replace the temp sender unit (<-- technical term?) after the second thermostat, and saw no change when the second one started to fail. I'm just wondering if sitting is killing these things. Truck is healthy as can be, but I know it doesn't get worked like it should on a regular basis.