A little over a year ago, I had my thermostat stick on me causing my truck to overheat. I replaced the bad thermostat with a napa one, and two weeks later, the same thing happened. Long story short, I have used a napa, carquest, checker, and a ford thermostat as replacements. Each time, eventually I end up getting a thermostat that sticks, sometimes in six months, and sometimes in two weeks.

I have a two year old radiator, a year old water pump, and a coolant filter. Coolant is always fresh, because of each time the thermostat sticks, all the fluid is usually boiled out, etc. Each time I change the coolant filter, there isnt any sediment or debris to be found.

Im stumped on what is causing this. Anyone have any ideas on why this is happening? From the obvious pain in the rear that a stuck thermostat causes, Im really worried about damaging the engine having this happen all the time. The ford factory temp gauge stinks, you cant see it getting hot until all the sudden the gauge goes into the red. I am going to install a different temp gauge, but that doesnt solve why the thermostats are going bad.

Thanks in advance!

 

I am leaning towards the possibility that your gauge is incorrect. You are troubleshooting correctly to get another one to verify the readings. Check you coolant cap as well, maybe you just need a new one.

 

Gauge works I guess. It is either normal, or in the red zone, hot. When its in the red zone, and showing hot, its way hot! Usually by then, either there isnt any fluid left in the system, or its dumping coolant out of the cap. Today, the engine was so hot, it was boiling water that I spilled on the top of the engine. You can hear the thermostat clicking and see the fluid level go down until it gets into the engine, followed by a huge gush of boiling fluid coming right back out of the reservoir.

If you let it sit, eventually things mellow out, but there isnt any coolant left in the system. By this point, you can add four gallons to the system.

Verified there isnt any coolant in the oil. Not getting any symptoms of a blown head gasket, or cracked head, etc. No oil in the coolant ever either.

Sometimes, things work great for a month or so, then all of the sudden, truck overheats. This has happened when the temp outside has been 20 degrees, and today when it was 100 degrees out. Ive had this happen with a trailer and a load being pulled, and with truck just driving to the store, etc.

Im stumped.

 

Are you using the right T-stat? The long one.

 

There are 2 stats you can use, long or short but the long one is for our truck. I dont know what the difference is except for one staying open longer...IDK

 

You can take one of the old thermostats and put in water on the stove. Put a cooking thermometer in the water and crank up the heat. When it gets close to the opening temperature, just stay close and watch for it to open.

A stuck thermostat isn't the only cause of boilover. A coolant leak or a pressure leak will cause the same thing. The cap, degas bottle, and hose connections are the weakest link. I'd have your system pressure tested.

 

I'm with Tugly!!!