What was it reading before they changed it? The thermostat only opens at a
specific temperature. It doesn't regulate the temperature. So in order for
it to run hotter now than before there has to be a change. If all that was
changed was the thermostat then all that it could be is the flow of the
coolant is either faster or slower than it was before. Either can cause a
Hmmm....I've argued this one before. *Of course* a thermostat
regulates the temperature. What do you think it's there for? If
a thermostat cannot regulate the temperature, there is something
wrong with the cooling system, whether it be inefficient, not
large enough, or not enough air flow through the radiator.
I agree Ian, if the system is designed right etc. the thermostat opening at
a set water temperature should in fact have set the running temperature. But
even driving conditions will raise or lower the temperature due to coolant
speed in the system. The coolant hast to have sufficient time to absorb the
heat from the motor etc.
Long story short if all that were changed was the thermostat it's probably
opening at an incorrect temperature or something else changed as well.
I wouldn't necessarily trust your dash gauge to give you an
accurate reading of what the temperature really is. Usually,
with a 195 degree thermostat, that's what you will see, providing
there isn't any other problem with your cooling system.
The thermostat has no bearing on the running temperature of the vehicle. It
only opens at a specific temperature. Even if the thermostat opened at 220
degrees the temperature would settle at 195 degrees if the cooling system is
1: He said it ran at the right temperature before the thermostat was
2: If all that was changed was the thermostat then there would have to be
either a restriction in the flow or not enough restriction (not likely).
We don't have enough information to diagnose the problem. Like why was the
thermostat replaced? Did the motor overheat severely prior to this repair
Please add a little more explaining as to how "Again... 180 to 195" will fix
Again... The thermostat does not control the running temperature of the
vehicle. Only at what temperature coolant is allowed back into the radiator.
Exactly, and that's how the thermostat controls the "running temperature"
of the engine. It's actually a very simple concept, and I'm always amazed
that some folks on these newsgroups don't get it. Cooling systems 101
and all that!
Brian, think about what you are saying. You are saying that
if the thermostat kept the fluid circulating in the engine block
(not allowing it to be cooled by the radiator) until the temperature
reaches 220 degrees, that "somehow" the temperature of the
engine will "settle" back to 195 degrees. That's not possible.
You also keep repeating your mantra about the thermostat having
"no" bearing on the running temperature of the engine! Of course
it does (as I already said)! Since I've already had this argument before,
let me nip any of the stock excuses in the bud. Any stock cooling system
should be able to keep the coolant temperature "at" the thermostat
opening temp. If not, then the cooling system is poorly designed, or
there is some sort of problem with the cooling system, probably related
to air flow. But if you have the proper air flow, the thermostat "will"
regulate the engine temp. If your fans aren't working, or you are sitting
in traffic and you have electric cooling fans and the a/c isn't on, if you
are low on coolant, if you have a restricted radiator, if the radiator fins
are plugged up....and on and on...then yes, the thermostat may not be
able to regulate the temperature. But when we are discussing this
issue, the assumption is that "all other things being equal", the t/stat
controls the temp.
> 2: If all that was changed was the thermostat then there would have
It probably is something as simple as a bad t/stat. It's certainly
not unheard of, I've seen dozens of them.
My motorcycle has a digital temp readout, so when it moves ever so slightly,
I can see it. When a turn the bike on after sitting all night, it reads
"---" until it gets up the the minimum thermometer temp of 68. While I am
cruising down the street it reaches 195, I feel a harm blast on my legs, and
I see the read out go from 195 to 185, then the warm blast stops, then it
climbs back to 195, another warm blast, down to 185, then it stops again.
Clearly, like you say, the thermistat is opening and closing to maintain a
185-195 opperating temp. When I hit a red light, I just sit there and idle
(no air movement) the thermometer just keeps climbing past 195, past 200,
past 210 (long light!) the cooling fan kicks on around 220 I think. Once the
light finally turns green, I start moving again, and the temp drops down to
185, then bounces from 195 to 185 as the thermistat opens and closes.
Coming home from Palomar, Via the 15 through lake Elsonor, my bike was fully
loaded, and it was about 105-110 degrees out, I was cruising at 80 mph, and
the temp was 202, if I sped up, the temp would climb, if I slowed down the
temp would drop a little. but it stayed as steady as the speed since the
bike was making as much heat as the cooling system could cool and the t-stat
didnt open and close, since they were both balanced, the t-stat just stayed
Right...and I think that it might be safe to say that your cooling
system "at that speed and load" is right on the edge of marginal.
But overall, it appears your bikes cooling system behaves very
much like a late model car with electric cooling fans.
With the heat blast I was going into, -I- was over heating! the bike was
doing fine. 650cc v-twin, me, saddle bags, tail bag, all full, head wind,
and about 105-110 out. Aparently, the cooling system only has 3.6 pints of
coolant/water in it. the manual says that if the temp gets past 248f, an
idiot light will come on telling you to stop and let it cool, and if it
reaches 284f (TWO HUNDRED EIGHTY FOUR!!!) the display where it shows your
speed will blink "HI" So running it at 202 or 210 even, is not really an
issue for the bike. I dont want it to get that high, but its nice to know it
can. Plus, bikes are not made for a big load (like towing) so I think the
cooling system is sufficient for 99.9% of my riding, any bigger and it
becomes extra weight. The bike is only 375 pounds.
The cooling system is operating properly, the old thermostat was 180 degrees
and was replaced with the new one to take the temp up to 210 degrees. My
question was what is the factory specs for the proper operating temp. Now
since my last post I drove it and the there is a noise when I feed gas. It
sounds like valves rattling when you put in cheap gas, but no gas was
installed since before the change.
New question, will high temp make that noise. The timing was never changed.
I don't want to harm the engine.
I want to thank all you who replied for this.
Factory temp gauges are notoriously inaccurate. I'd hook up a mechanical
temp gauge and see what the temp really is.
The thermostat controls the minimum operating temp while the radiator
controls max temp. So, if everything works right, a 195 degree stat should
keep the temp at *about* 195 degrees.
If I am wrong, I'm sure Marshy will let us know :-).
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.