Many years ago in the days of cast iron blocks and heads and all steel radiators we changed thermostats periodically lest they stick open(bad) or shut(really bad) at the worst possible time(funny how that usually seemed to be the time we changed them). I'm getting ready to change anti-freeze in my '91 Honda Civic and am pondering whether to get a new thermostat. My records tell me that I last replaced it at 121,215 miles, and the car now has roughly 267,700. That means it has been 8-10 years or more since I replaced it.

My impression from doing several flushes on this car is that the coolant stays cleaner in an aluminum engine, so there isn't as much crud flowing through the thermostat and therefore maybe the little buggers last longer. What has been your experience?

Thanks for your input, friends.
Andy

The only thermostat I had fail was on a car that was 36 years old and the thermostat was an original one. It had a cracked bimetal.

They are cheap though.

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Luke 22:36

You're joking.. right!

My 2006 Jeep Rubicon has 214,000 less miles on it that your Honda... I'll never reach your mileage!

I'm not even sure that I would flush the system and change the fluid. I haven't changed a thermostat in 25 years at least. It used to be very, very common, and if I had a no heat condition on any car or truck, that was the first thing I changed.

I think cars are just that much more reliable these days.

Ha Ha, I hear you my '04 GMC Sierra just turned 50k.

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Dum vivo cano

Change it. It's not that expensive to buy and in most cases it's just two bolts holding the housing on. Of course that doesn't mean it's easy to get to those two bolts. BTW, if you haven't done it recently, change the hoses while you're at it.

CW

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μολὼν λαβέ

Change it, at that age and mileage it's easier to change it now than in the auto store parking lot in the dark.

My youngest daughter's CRV had well over 300,000 miles on it when we traded it in. I don't know if the thermostat was ever changed. I know I never changed it but we did buy it used.

My 95 Camry with 167,000 miles (recently purchased) was running cold. Got a STANT US made replacement thermostat for $8, and new gasket for $3. Turned out that the old rubber gasket had failed and was holding the old one part way open. Since I was in there I replaced the thermostat anyway. Hoses are made of that new stuff epdm, they seem to be just like new. Haven't seen one fail on a newer car, but my area has a pretty mild climate, your mileage may vary....

If you are already going to be into the engine where the thermostat is, then go ahead and change it. Just like you do the water pump when you change the timing belt. I've had two Accords - a 1987 and a 1993. I gave the 1987 to my niece with 276,000 on it (she promptly put in an aftermarket stereo, had it broken into and trashed) and sold the 1993 with 312,000 on it when I bought my 2000 Oldsmobile. I sold my 1988 Mazda 626 a couple of months ago that dad bought new off the showroom floor. 401,000 miles. Electrical system finally croaked but still had the original clutch. Take care of the maintenance and they'll run a long, long time.

They arnt expansive and while youre getting stuff fixed its not a bad idea to do that too. Its a $30 part, if that, but when it goes it could end up costing you a car. My Toyota Solara has 220k and ive changed that part twice. Each time during a 100k maintenance. It gets changed with the timing belt and water pump.


Sent from my DROIDX using Tapatalk 2

The last one I had go bad was in my suburban pulling my 29' trailer. That thing got so hot so fast it's indescribable. I thought I'd blown a head gasket so had it towed to town and called a friend to come out and finish pulling the trailer in. Thank goodness for good friends. Bottom line, lesson learned.

Now whenever I change antifreeze or hoses, changing the thermostat is automatic. Experience tells me they don't quit working in the garage or near home. Cheap to do, and about as easy as it gets. Pay attention though on some cars. I've heard some have a gnarly way to bleed the air out of the cooling system to avoid trapping it in the engine and really screwing things up. If you're doing it yourself, just find it on the net to make sure.

+1 on the bleeding procedure. Cars these days have lower profiles and sometimes the engine is higher than the radiator. Each design has its own way to do so.

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Dum vivo cano

Thank you for your response, sir. As I indicated in my post, I've done this several times, and thus am quite familiar with the procedure. This model has a bleeder screw between the upper hose and the head.



Thanks to all of you for your input. I've done virtually all the maintenance and repair on this thing for the last 17 years, but it seems that there is always a little more information to be had.

Regards,
Andy

I have a 1998 Accord, 220,000 miles. Yes, I change the thermostat and coolant, every 60,000 miles.

I also change the transmission fluid every 60,000 miles, it is a simple drain and refill.

Even more important is changing the brake fluid, especially on GMs'.

The brake fluid, I use a turkey baster, suck out of the master cylinder what I can, and refill. I do this twice a year.

I save the old brake fluid, it is a great paint remover for restoring old tractors.

The coolant is also recycled, I mix it 50% with water and use it as ballast in garden tractor tires - more multi-tasking.

The Honda got its first set of brake pads at 208,000 miles. The shoes are fine.
My '99 Silverado 2500, 210,000 miles, has the original brakes, and they look great. Discs front and rear.

I change the oil at whatever the odometer reminder says to do.

My daughters '97 S10 was getting hard to shift the manual transmission, changed the oil and all was good. That was at just over 300,000 miles.

I have never had to repair a transmission.

Every Thanksgiving, the daughters, son-in-laws and me get together for a fluid changing party after turkey. I buy the supply's, we change fluids, then shoot the empty containers afterward!!

Am I cheap, or what!!

The truth is the Japanese car manufacturers forced the American manufacturers to make better cars. My father used to trade in his cars when they reached 40,000 miles. Do you remember "vapor lock"?

I used to keep my cars until they died--usually when the tranny went bad. Then I switched to manual transmissions and my cars lasted until the anti-lock brakes went (too expensive to repair).

While your at it, don't forget the Blinker fluid. It is a Honda Spec Part item so you need to get it from them.

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Still Running Against the Wind

The one car I had that consistently vapor-locked was in fact Japanese. In the last year of carburated Z-cars (1974) Datsun switched carb manufacturers from SU to Hitachi. Big mistake. Wasn't bad in mild Seattle, but when I went over the mountains to Spokane in the summer to see family I bought bags of ice from the speedy-mart, kept them in an ice chest in the back, and when the car died on the freeway I coasted to the side and dumped ice on the intake manifold. That'd get me another hundred miles or so. I finally retro-fitted the earlier model carbs (technically illegal, even though it produced lower emissions afterward), and no more problems.
Those Hitachis carbs are so bad that carb rebuild places won't accept them as cores; you can't rebuild them.

One of the signs of a failing thermostat is temperature flux on your coolant temp gauge. This doesn't work for idiot lights. Corrosion and dirty coolant really don't effect the longevity of a thermostat. Sometimes they just fail.

I tend to Change mine about every 100k miles at the cost of $10. If it makes you feel better. There is a thermostat out there called a "Fail safe" thermostat. It's a few more dollars, but when it fails it locks back in the wide open position. You could at leased get home on that.



MotoRad - Fail Safe® Thermostat

Here in my part of AZ we just pull them and throw them away.
Never gets cold enough to need them, all they're for is letting the engine warm up before letting coolant flow.

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Hold my beer and watch this!

The thermostats of today are just plain made better...change it if you want to, but the older I get the more I follow the "if it aint broke, dont fix it" doctrine. I am 50 and definately remember the days when they went bad, I have changed several in my time. Also, when you do the flush and fill on your Honda...most Honda's have a little air bleeder on the cylinder head near the thermostat housing. If you dont open it and bleed off the air bubble you wont get enough coolant back in the block. You will think it is full and the first time you drive it the air bubble will expand, blow out what little bit of coolant it did have and run hot. If a female is driving it when this happens you will need a new engine...I have yet to meet one that would stop driving because a warning light is on. If I have learned nothing else in my 50 years of this life it is that the more beautiful the woman the less chance you have of her ever making a good sound decision.

Bad decision...the colder an engine runs the faster the cylinder bores wear out. It is a proven tested fact that cast iron cylinder bores wear the longest with a 190-195 thermostat. Even a 160 like the old 60's cars used will accelerate the wear. Thermostats heat the engine to the proper temperature for the oil to do it's job. Many people thought the cooler the better and it seems to make sense...but we aint talkin' gun barrels here. You need a thermostat.

During the Summers here, it's 150 under the hood BEFORE you even start the car.
Not a joke, not an exaggeration.

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Hold my beer and watch this!

and to add to what you said....

taking out the stat will make the car overheat! Get on the hwy and run it awhile and watch. The coolant NEEDS to stop in the radiator to be cooled. That is what the stat is there for. But you know best I'm sure.
Arizona would be the last place to not run a stat.

You run 75 MPH and the motor gets hotter and hotter.... the coolant just keeps getting hotter and hotter for the above stated reason.
How long do your motors last? You change em every 2500 miles with the oil?

Basically it's needed for above reasons to achieve the most economy, and least emissions.

Sir,

Please read post #14.

Andy

Here are some facts about the cooling systems in cars today.

The car needs a thermostat for the reason stated above. It can over heat the car because the coolant doesn't spend enough time in the radiator.

The thermostat needs to be what OEM recommends. Some cars have 2 coolant temp sensors 1 controls the gauge and the other works with you PCM. The one for the PCM tells the PCM how much fuel to add from the temp of the coolant. When you start your car your PCM adds more fuel to heat the engine faster. When the coolant is at temp the PCM resumes normal fuel flow.

When refilling the radiator with coolant the car has to be on flat ground or with the radiator cap above higher than any other part of the cooling system. Failure to do this can cause an air pocket in the system. An air pocket with cause an extreme hot spot in the engine. This can cause detonation, pinging, week spot in the block, heads, or intake. Any of these will cause severe engine damage.

You need to have the correct PSI radiator cap. To high and coolant won't vent into the overflow. To low and you could lose coolant.

Coolant needs to be mixed with water. Ideal is 50/50 hotter areas like AZ you may want 25% coolant and 75%water. Too much coolant will over heat the car. Too much water will pop out the freeze plugs or crack the engine.

I don't buy pre-mixed coolant. It's not always mixed. Plus a gallon of pre-mix is the same price as a gallon of straight. A gallon of straight coolant will make 2 gallons of 50/50 mix.

When in comes to older cars, most cars of that year range take a 3yr/30,000 mile coolant. You may be going over the milage limit on your vehicle but your owners manual should give you a maintaince timeline. I would replace the thermostat while you are there.
Also, if it is easy to access, you may want to flush your heater core out and radiator. I usually just take a garden hose and flush both out going the oppisite direction of coolant flow. Over time deposits will build up in the cooling system and on the smallest places(heater core and radiator) these deposits will restrict the flow much quicker. Flushing these spots out will increase the flow and increase the heat transfer for the engine and for you during the winter time.
To the OP, i know you know how to bleed the cooling system on your vehicle but useing this tool: Lisle 24610 Spill-Free Funnel : Amazon.com : Automotive can make things very easy. I always use this when filling the cooling system on any vehicle. Helps keep the coolant level above the thermostat aiding in bleeding and greatly helps in not spilling coolant.