Q. re: thermostat temperature ratings

[Pajamarama]

I will be replacing my Accord's thermostat soon.

Looking online for a replacement part to purchase, I have noticed that they come with different temperature settings.

170 deg F
180 deg F
195 deg F
etc

Is this temperature rating the temp at which the thermostat begins to open or is fully open?

Thanks.

 

[Cristobal]

I bet when it begins to open, as a little opening is as good as a big one, unless the temperature of the environment is very, very hot. I may be wrong. Caterham will know for sure if he sees this.

 

[440Magnum]

Its generally the temp at which it starts to open.

 

[bepperb]

If you test one in a pot of water they open surprisingly fast over a very short change in temperature. I'm not sure if it's the beginning or the end, but the change doesn't take 15 degrees.

The OEM Honda thermostats are about twice as heavy and seemingly much higher in quality that what you'll find from a store. If the price is even close go dealer on this part.

 

[LeakySeals]

In the days before the ECU lowering thermostat opening temps was helpful for some situations. Not anymore.

 

[Donald]

I would not pick and choose, but get the one that it came with.

 

[Pajamarama]

Originally Posted By: bepperb
If the price is even close go dealer on this part.


Depends what your definition of "close" is. $7 online (need to order other stuff too so additional shipping is marginal) vs $24 at the dealer.

According to the Repair Service Manual for my Accord, the specs on the thermostat are:

Starts opening: 169 - 176 F (76 - 80 C)
Fully open: 194 F (90 C)

Which is why I wondered what the temp ratings on the thermostats I found online corresponded to.

 

[SrDriver]

Check with your local parts house or dealer.

I am guessing the 195 would be what it calls for?

Do know that the 195 would give the best economy.

 

[ARCOgraphite]

How 'bout cars like my Honda Fit that dont have an external exhaust manifold - butinstaed its fully cast in the Aluminum head and then but a single tube external collector feeds right into the #1 cat.

[thinking aloud: How do those Honda Head gaskets hold up?! You would think water jacketing would defeat the purpose of maintaning high exhaust temps in to the cat #1. Maybe the supersonic velocity of the cast in individual small port "fingers" makes up for the wather jacketed cooling effect]

 

[SteveSRT8]

Originally Posted By: LeakySeals
In the days before the ECU lowering thermostat opening temps was helpful for some situations. Not anymore.


Very platform dependent advice. You simply can't make broad sweeping statements like this anymore.

For instance, the new gen Hemi community has learned that a 180 thermostat is one of the best mods you can do to a Hemi in terms of dollars per grin! Huge gains when the computer perceives cooler temps in this design.

 

[SHOZ]

Most t-stats should have a start to open and fully open temp rating. Fully open many t-stats will block off some internal bypass flow of the coolant so coolant can them be drawn in from the lower radiator hose.

At least the reverse flow ones I've see are.

 

[Trav]

Quote:
$24 at the dealer.

Best $24 you can spend. Most aftermarket ones have really gone down hill.
Years ago Stant was a very high quality reliable thermostat now its not worth a pee hole in the snow, light and tinny.
Its OEM only for me.

 

[Virtuoso]

I've had horrible luck with replacement thermostat's. This is one part that defiantly does not get 'fixed' until it is broke!

 

[Tegger]

Originally Posted By: Pajamarama
I will be replacing my Accord's thermostat soon.

Looking online for a replacement part to purchase, I have noticed that they come with different temperature settings.

170 deg F
180 deg F
195 deg F
etc

Is this temperature rating the temp at which the thermostat begins to open or is fully open?

That is the start-to-open temperature.

Your engine requires a 78C thermostat, which equates to 172F. This thermostat is fully-open at 90C, or 194F. The equivalent aftermarket unit would be a 170.

It is a bad idea to use aftermarket thermostats in your Honda. I recommend you spend the extra few bucks and get a genuine Honda thermostat from the dealer (likely branded "NTC"). Expect to spend about $35.

 

[mechtech2]

The spec for a thermostat is the OPENING temp.
Hotter ones are best for efficiency.
Oil will be hotter and a bit thinner.
Less heat is lost to constantly heating up the CC walls and cylinder walls [cooler will take more energy/heat from the combustion gasses - a loss of energy ]

With special tuning, a cooler thermostat can allow more power.
But I'll bet the 195 is best for the street for a bunch of reasons. Even is GA, better heat in winter.

 

[Pajamarama]

Epilogue: I ordered the Gates 180 degree model from Rock Auto and installed it this afternoon.

When I opened up the thermostat housing, there was no thermostat whatsoever. Completely empty. No wonder my car never warmed up! I just finished putting it all back together - no leaks and the temp gauge warms right up.

I am glad I put one in there before it started to get really cold.

 

[Samilcar]

You should get a nice boost in fuel mileage now as well (in addition to having toasty tootsies).

 

[mechtech2]

Gas mileage, engine ring sealing, and wear should be improved.
180 is low nowadays, but way way better than none!