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Broken thermostat?

95 Corolla, 262K miles. Had a tune up with coolant change about a year ago.

Temperature gauge has roughly the “C” at 8 o’clock and the “H” at 10 o’clock. Anyway, it USED to go up to about 30%-40% of the way from C to H. Now it seems much lower, like 10%-15%. Even when the car is warmed up…and it’s lower on colder days.

Also the choke stays on much longer in the morning. It won’t go into overdrive for a long time, maybe twice as long as before.

What do you think? Broken thermostat? Stuck? How much does it cost to replace?

Or is it that the coolant change used much harder to warm up coolant? The old coolant was about 5 years old.

I’ll bet replacing the thermostat will fix it right up. But before that just for kicks check the coolant level.

you can buy the thermostat and gasket for under $30 bucks, plus your elbow grease, and an hour, you will be in great shape.

Like was said above make sure your coolant is full. The ecm prevents overdrive until the engine warms up for emissions.

I agree. Your thermostat is stuck open. The low temperature is causing your engine to operate in the open loop mode which prevents the transmission from going into overdrive. You have a fuel injected engine - there is no choke. If you can change it yourself it won’t cost much. If you have it done add in about an hour labor for about $100.

After almost 10 years and 262,000 miles, your thermostat had a right to submit its retirement papers. You will make up part of the replacement cost for a new thermostat with better gasoline mileage.

it’s actually about 20 years. Do you think they might have done something to it to get it stuck open when they replaced the coolant?

I wonder if it’s possible to unstick it, or if it can only be replaced.

“it’s actually about 20 years” At my age, time goes so fast that it seemed like only 10 years. You can’t unstick a thermostat. It would be easier to put a new filament in a burned out light bulb. You would have to remove the thermostat anyway and the price of a new one is pretty inexpensive.

Do you think they might have done something to it to get it stuck open when they replaced the coolant?
I seriously doubt it, you got 20 years out of it, what else do you want.

Unstick it, really? It’s a $6-$20 part depending where you go and about 30 minutes maximum to replace.

Back in the day I used to change the thermostat (and radiator cap!) every other coolant change - 4 years.
Working the old one by hand vs the new one I could feel the beginnings of stickiness.
Now with long life coolant I still plan to change the 'stat every other coolant change - 10 years.
20 years to failure is pretty good. Change the cap and maybe hoses too.

The coolant change had absolutely nothing to do with the thermostat sticking open. They just do that as they age. I’d be surprised if this is the original thermostat as they don’t usually last that long. You have enough age and miles to have had two thermostats age out.