how can you tell if your thermostat is stuck?
If it’s stuck open the engine will not reach correct operating temperature. This will decrease gas mileage and you won’t get much heat from the heater.
If it’s stuck closed the engine will quickly overheat.
Thermostats are inexpensive. If you have any doubts about yours, replace it.
Thanks! How can I tell if it is the thermostat or not? All of the fluids are at their correct levels. The coolant mixture is correct at 50/50 in Shreveport, LA where it is steaming hot anyway. Still, the engine is running up to the red zone, which I control by turning the heater on. Just had a new water pump put in last year for 900 bucks. Is it hard to replace the thermostat? Can I do it myself? Does it sound like the thermostat? It doesn’t overheat really quickly. Doesn’t go all the way red either. Should I just put straight coolant in the radiator? Could very well be the thermostat. Why, oh why, wasn’t I born to work on engines?
There are other causes for your car to overheat. If the radiator is half clogged the engine will overheat. If the electric cooling fan does not come on or comes on too late, your engine will overheat. You need to have all these things checked out.
It would help to know how old your car is. On newer cars I recommend to change the (long life) coolant and thermostat every 5 years or when the manual says so, whichever comes first. On older cars with regular green antifreeze change the coolant every 2 years and the thermostat every 4 years.
Besides the heavily clogged radiator, if the car continues to run hot when you drive it on a highway, then it is likely to to stuck-closed thermostat. If the car cools down when you drive it on the highway, then it’s radiator fan, radiator fan switch or something that has to do with cooling the hot fluid in the radiator.
If the thermostat is stuck, hot water is flowing around the engine and cannot get out. So, the only way to cool the water is by turning on the heater. However, if the thermostat opens normally, but the hot water in the radiator cannot be cooled, then driving on the highway would cool it by letting enough cool air through the radiator.
Make model and year of car or truck or boat? Why are you asking the question? What makes you question the thermostat?
Thermostats are designed to fail open not closed. Of course sometimes they still fail closed. Most are cheap and easy to replace so that is what I would do first, most of the time. You can remove the one you have and put it in a pot of water with a thermometer and turn on the heat and watch it.
However there are other things that can make someone think of the thermostat.
$900.00? Did Jesus do the work? Holy cow, I certainly hope that you got more than a new water pump for $900.00! It is easy to replace a thermostat . . . change the radiator cap at the same time, sounds dumb, but trust me on this. Also, don’t put straight coolant in the radiator, follow the manufacturers recommendations. Rocketman
I have come across some electrically monitored thermoststs that are priced North of $100.00 (BMW) you don’t want to put one of those in “just because”.
How great thou art! Aha! It must be the thermostat! The engine does not cool down when I drive on the highway. The temp gauge steadily increases. I put extra water in the coolant reservoir, which I thought would be useful in preventing a red-zone overheating situation. If the reservoir is meant to house expanding water from the radiator, then I have erred. The only way to cool the engine when it runs hot is to turn on the heater, so it must be the thermostat! How exactly do I change it? It’s a 99 Dodge Durango 4 door SUV 4 by 4. Sucks up the gas too, at 14.9 mpg. Love it though. To err is human, to love divine. I have done both!
It wasn’t me that thought it was the thermostat. Does that get me off the hook? My uncle thought it might be the thermostat. He says that if it goes bad it can ruin an engine completely. I drive a 99 dodge durango 4 by 4 SUV. sucks up the gas at 14.9 mpg. It is running hot on the highway and only cools when I shut it off or turn on the heater. how exactly do I change the thermostat? I can’t pay anyone else to do it, and my hubby and I are divorcing now living in different states. I am woman, hear me… beg! What do I do next?
Follow the top radiator hose back to the engine. It attaches to a metal piece shaped a little like a funnel. Inside that piece (thermostat housing) is the thermostat. It’s probably held to the main body of the engine by two bolts.
You’ll need a wrench to remove the bolts. Don’t buy a tool kit with a zillion pieces. If you charm the parts store guys a little they’ll let you take a wrench socket out to your truck to see if it fits. One may even go out and try it for you. A socket, a no-name or Sears ratchet wrench and an extension. That would be an inexpensive start to your DIY toolkit.
Go to an auto parts store and buy a thermostat and gasket. Those are ~$20. Get the same temperature thermostat as the original. Get a jug of “universal” antifreeze to top off the system and some anti-seize compound for the bolt threads.
With the engine COLD put a clean pan under the radiator. Take off the radiator cap and open the drain at the bottom of the radiator. Drain about 1/2 gallon of coolant out and save it to pour back in, or drain the radiator and put all fresh coolant in later.
Loosen and remove the bolts. If the housing doesn’t pull off easily tap on it with a small block of wood. Make note of how the old thermostat is seated and put the new thermostat in the same way.
Carefully peel off the old gasket. If any of it is left scrape it off with a plastic knife. Put the anti-seize on the bolt threads, hold the housing in place and feed the bolts back in. Reinstall the bolts evenly: Start the threads by hand on each side, then turn them as tight as you can with your fingers, both sides. Then “snug” them with the wrench and tighten them moderately in stages. I won’t get into the torque wrench thing.
Fill the radiator back up with the removed coolant or fresh 50/50 mix. There may be an air bleed fitting near the thermostat. Looks like a bolt with a hole in the middle. Loosen that until a little coolant comes out. Re tighten.
Leave the cap off and start the car. Refill the radiator if necessary. After a minute or so put the radiator cap back on. Let her idle a few minutes and warm up. Watch for leaks. When the top radiator hose gets firm you’ll know the system is holding pressure. Shut off the engine.
After the engine cools off refill the coolant reservoir.