Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Cooling System - Thermostat

I changed the thermostat on my car about 6 years ago, and I have only driven about 16,000 miles since then. Should I change the thermostat now or wait until I have put on another 15,000 miles or so?

If the thermostat is working why would you want to change it out? I would wait until it shows signs of trouble.

I have heard there are some people who replace the thermostat at regular intervals, or whenever they replace the coolant. I consider this action quite unnecessary. A thermostat is not a wear item. The replacement part may well have a shorter life expectancy than the current part, who knows. Leave it alone as long it as is working properly.

Confirming the other replies. The stat is not an item that requires regular maintenance. There’s a Federal regulation that if it gets stuck open the check engine light must go on. If it gets stuck closed then you’ll know about that from the gauge. Otherwise, ignore it.

When I drove every day I changed the thermostat every 4 years (every other coolant change).
I always felt the action of the new vs old (pushing open with fingers) and the old one always felt like it was getting sticky.
So yes, they do wear out like any moving part.
Now that I only drive 2-3 times a week I change it every 10 years (~40k miles).
Again, that’s every other change of long life coolant.
I also change the radiator cap when I change the thermostat.
I’ve seen cars with the thermostat stuck open: wasted fuel.
I have a friend whose thermostat stuck closed on the interstate; not a pretty sight.
I always use an OEM thermostat, so I’m confident it will last as long as the original.
Thermostats are not expensive, why take the chance?

Just my 2 cents, but I consider the thermostat a wear item subject to failure at any time and change the ones in my cars about every 4 or 5 years even if they do not show a problem at that time.

Many an engine has been roasted because of a 5 or 10 dollar T-stat. This usually goes hand in hand with comments about the temperature gauge was fine, it was only 10 miles more to the house or garage, etc, etc.

Thermostates don’t tend to wear, but they can malfunction. Generally you just leave them alone until there is a problem.

I remember back in the late 1940s and early 1950s when motorists would remove the thermostat in the summer. In fact, Tom McCahill, who had a column in Mechanix Illustrated magazine wrote in his book “What You Should Know About Cars” claimed that he he had cars that he ran without a thermostat and these cars did very well.
I remember my dad used a thermostat that opened at 160 degrees in his 1939 Chevrolet. He used a non-permanent antifreeze that DuPont marketed under the name of Zerone. This antifreeze boiled at 180 degrees. DuPont’s ethylene glycol permanent antifreeze was called Zerex. Many people ran water with rust inhibitor in the summer time back in those days.
Today’s cars wouldn’t do well with no thermostat and straight water. It may not have been the best idea back then either.

As a kid pumping gas in garages in the 60’s, I remember mechanics removing thermostats to cure overheating problems.

Ford did a study in the 70s where they took new cars and ran them around a track, continuously for 100,000 miles. They’d stop long enough to change the oil and change drivers. The goal was to not let the engines cool down.

At the end of the 100,000 miles, they tore down the engines and measured the engine wear. The noteworthy point was the cylinder walls were barely worn. The amount of wear was the amount the engineers expected on an engine with less than 10k miles.

@JoeMario–the wear comes when an engine is first started and is getting up to operating temperature. Running a car continuously for 100,000 miles probably doesn’t create a lot of wear. When I lived in Southern Illinois, there were engines that ran the pumps that pumped crude oil from the ground that ran continuously and were treated to an oil change just once a year.
When an engine isn’t run continuously, it is very important to have a thermostat that gets an engine up to operating temperature and keeps it there.

On older cars and in a pinch where you don’t have access to tools, gasket, sealant and replacement parts, you could take the top hose off, take a sharp screw driver along with a hammer and punch a hole in the thermostat. Usually you could get to it, right through what the radiator hose was attached to so you wouldn’t need to break the seal.
I’ve done that once to get a friend’s car to get her home.

By using the word wear I mean that it’s an item with moving parts that is subject to wear or malfunction.

In the past, I’ve been on the road several times and suffered a T-stat malfunction. Generally this was a simple matter to get around at the time because the T-stat was easy to access and remove until a repair could be done. Changing the T-stat on occasion can swing the odds into the car owners favor and prevent those middle of the night and middle of nowhere failures.

In some cars like my Lincoln I cringe at the thought of changing or removing a T-stat while on the road. It’s a major job that really requires removal of the oil filter, a special tool, and working underneath the car after draining the entire cooing system; with the obligatory dumping of coolant into the face of course.

Any time I replace a stat for whatever reason, (maintenance, repair, etc.) I install the fail-safe thermostat. It cost a couple more bucks but well worth knowing that a failure will more likely keep the engine from over heating and causing more damage.

Like everythiing subject to flowing liquids, T-stats are subject to getting gumped up as well as to wear from the movement of the mechanism. As Steve and OK4450 suggested, many folks believe in changing them proactively, usually when they change the coolant out. I’d wager a guess that the overwhelming number of people don’t pur fresh coolant in routinely and never change their T-stats out. Personally, I’d strongly recommend changing both the coolant and the T-stat at least every 5 years.