2004 Accord heater temperature?

Well it may be normal for Hondas, but not so any other car I've owned.
Once warmed up, my 95 Camry would sit rock solid at the half way
engine temperature mark regardless of whether I was idling for long
periods, driving hard, or just tooling around town. You did get a
*little* extra heat when idling if you just reved up the engine for a
brief period. That had nothing to do with the temperature; it just
speeded up the water pump and moved hot water through the heater coil
more quickly. Same with my Volvo. Same with my Mazda. Same with my
Dodge Caravan. I've never experienced a temperature gauge dropping
while idling. That's a part of what themostats are supposed to
control.

 

I didn't say the coolant temperature would change. What I said is that under
load, the engine produces more heat. This is true for your Camry, Volvo,
Mazda, or any other vehicle that has an internal combustion engine.

Here is what happens:

- Engine at idle. Not very much heat produced. In order to maintain constant
coolant temperature, thermostat closes, causing limited coolant flow. Not
much heat is getting to the heater core, so not much heat in the cabin.

- Engine under load. Much heat is being produced. Thermostat opens, allowing
lots of coolant flow, transporting heat from engine to radiator. Coolant
temperature remains constant, but because of the overall flow rate of the
coolant, lots more heat energy is being moved away from the engine, both to
the radiator and to the heater core, thereby causing much more heat to be
available in the cabin.

End result is that when you accelerate hard, you will get more heat in the
cabin, within seconds. Which is what the original question was about.

 

I have an 02 Accord SE 4cyl and have observed this when extremely cold
outside. Usually only happens during the start of my drive. Once the
engine has gotten to temp I have never seen it come down. I have even
had it happen with cold inside cabin and air on recirc.

This goes ditto with my wife's 03 Civic LX, if it is cold enough the
coolant temp gage will drop when at a stop until the engine has
reached it's normal temp, once there it stays.

 

Yes and no.

Engine at idle and the thermostat should close partially. That
restricts the flow of water to the radiator, but has no impact on the
flow of water to the heater. The speed of the engine does affect the
water pump which affects the flow which is why when you just rev up
the engine momentarily while idling, you'll see an instant increase in
heat. It's water flow. That has nothing to do with how much heat is
being produced by the engine.

Engine under ANY load above idle, the themostat continues to regulate
the water temperature, but the water pump is now moving the water at a
sufficient volume to provide full heater function. Moving the water
faster only serves to return hotter water back to the engine. It does
not produce more heat in the cabin.

So, my point here is that a normally operating themostat (at least in
the experience with every car I've owned) keeps the engine temperature
steady whether at idle or cruising speed. The only variable in the
interior heat equation is the flow of water which is a bit low at
idle. Heat produced by the engine has no impact on any of this. An
idle produces far more heat than is required to keep an engine at
operating temperatures.

And my earlier point, was the my Honda is the first car I've ever
owned where the engine temperature gauge drops while idling in cold
weather. (The earlier poster noted that as well, I think.) That really
shouldn't happen. Seems to me that one of two things are going on.
Either the thermostat is not set up correctly to close partially when
the engine doesn't require as much cooling power, or the temperature
gauge is mounted in a location that cools down without flow through
the radiator. A gentle rev of the engine brings heat inside (as per
above) and the gauge goes up quickly as well. That suggests to me that
under low flow conditions, the water is not circulating very well
around the sensor. If it really were that the themostat was letting
the water cool down that much, it would take time for the temperature
gauge to climb back up. The engine could not possibly heat up and
transfer new heat to all that water with a 5 second rev of the engine.

Bottom line is that you get an instant surge of heat when you rev up
an idling engine due to increased water flow, not because the engine
heats up.

 

Hmmm, different mfrs rig their temp gauges differently - Honda has a
plateau of zero needle response from 85C to 100C; it would not surprise me
to learn that others have an even bigger plateau - it's not a precision
gauge. if you want to read your engine temp accurately you need a full
response needle but that'd probably scare the shit out of most buyers... to
see it oscillate so much.

It *may* have something to do with the Honda aluminum block as well which
is not really a block in the same sense as most other mfrs; the Camry has a
cast iron block. Then, as mentioned by someone else, there's the position
of the temp gauge - Honda's are on the end of the cylinder head, under the
distributor where they essentially read the temp of the coolant on its way
out to the radiator... so if you're running the heater (essentially a
mini-radiator/fan) in extreme cold, so that the thermostat is closed, there
is no appreciable outgoing coolant there anyway.

BTW I certainly recall that the 70s thru mid-80s VWs I owned had very poor
heating in extreme cold, even when cruising on the freeway at 70mph or so.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

That's interesting. I think the positioning may in fact be what is
causing these variations. Engine temperatures just don't vary that
much and that rapidly, in my experience.

Those old air-cooled VW's were great little cars, but the heat was
awful.

 

And deadly. A buddy in high school had one where the exhaust gas heat
exchanger was rusted through and you'd darn near get CO poisoning!

 

Luckily the defrosters worked badly as well, meaning that you often
had to have the window open to keep the fog down ... : - )

 

Well no - I was talking about Rabbits/Jettas. Actually the Beetles, from
~1962, had gobs of heat from the exhaust heat exchangers - the trouble was
you couldn't regulate the airflow and its temperature independently.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

I agree. We had a '66 Beetle and operated it in temperatures down to
45 degrees below 0F. Never a problem getting enough heat. Just as
George said, difficult to regulate.

Dick