I have a 98 accord with 120k 4-cyl. miles. I drained the radiator and filled it back up with factory Honda 50-50 coolant. New HONDA factory thermostat installed. Now, i know i have the right concentration of coolant because it came pre-mixed by honda. The thermostat is also Honda. No leaks and level is perfect in radiator. When i started my motor and got it at peak temperature i noticed the needle on the gauge is pointing lower than it did before (less than 1/3). When i drive i notice slight movement of the needle. It moves down very slightly and then back up very slightly. I know the needle was not pointing exactly where it is pointing now. I've had the car since new and this is the first time i have seen fluctuation in the gauge. Is there anything wrong or is this normal? Could the problem be with the temperature sending unit or gauge? What puzzles me is the movement of the needle on the temp. gauge started immediately after the radiator flush and i know i used HONDA factory 50-50 coolant. All comments appreciated.


Modified by Elvis1977 at 2:28 PM 3/25/2004

 

Make sure you beled the coolant system, by caefully unscrewing the 12mm scew behind the valve cover. Also double check that you have toped off the radiator once it's cool.

 

exactly where is this bleeder screw? Coolant level perfect.

 

Bled the screw on thermostat housing and no change with the needle. Anybody with clues?

 

When you flush the system...honda's usually will show cooler then normal afterwards.. this is totally normal

 

Well, I did not flush the entire system. I just drained the radiator and refilled with 50-50 pre mixed Honda coolant when engine was stone cold. Also, why does my needle slightly move up and down while driving?

 

well, there's no point to flush half of the cooling system.
you probably need to bleed the air out of the system also.

 

I bled the screw on top of the thermostat housing and no luck. Is there another place to bleed the system?

 

My '98 only has the one bleed screw near the t-stat. But when I did it I got air bubbles at the radiator cap also. Before you open anything up, wait until it's cool, & squeeze the radiator hoses. If you have air bubbles in either hose, you'll hear it sloshing. You should only hear that funny little pin rattling in the t-stat. You can hear & feel whether you have air pockets. After driving the car around & cooling it off, air should collect in the hoses.

Did you have the heater temperature dial set all the way to hot? Air can hang out in the heater core, too.

 

Your abolutely right! When my engine is cold all I hear when I squeeze both hoses is the pin on thermostat. I'm sure I have no air in the engine. I ran the engine with the heater/blower on maximum and removed the radiator cap and no bubbles seen. What I don't understand is why the needle is pointing lower than it did before i started. Honda premixed 50-50 coolant used, and new honda thermostat replaced. I know i have the right concentration, but why did the needle move lower than it was before? Also, why does my needle move very slightly up and down while i drive? But never even close to half-way. More like 1/3 way from cold marking. Does the thermostat open and close while driving? This might explain the slight needle movement. Comments appreciated.

 

The t-stat IS supposed to open & close; it's trying to hold a constant water temperature. When it's 15F outside & you're coasting down a hill, it's gonna be pretty much closed. When it's 115 in HotLanta & you're driving up a big hill, it'll be open wide.

Even a genuine Honda t-stat is a simple little stamping. There's tolerances when they're made, so you got one that's just a bit colder this time. That's not a bad thing! Besides, I think 1/3 scale is more 'normal' than 1/2 anyway. Probably your old t-stat had gotten 'hotter' as it aged. (Very slowly, so you don't notice it.)

 

You have made some very logical comments and I think you are the best wizard on this web-site. But listen to this. I don't think the thermostat is to blame. When I drained the radiator the very first time the needle pointed exactly where it is pointed now WITH the original thermostat from factory. I then thought it was the thermostat so i put in a brand new exact honda one and the needle still points a little less than 1/3 from the cold marking on the gauge. No difference, but still a good idea to put in a new one whenever a flush is done. Now, if you look carefully on the coolant from Honda, is says "long-life coolant 50-50 no need to add water". Maybe this is why the needle points lower than before.

 

Well then I suppose it was the fresh coolant that brought the temperature down a bit. How old was the coolant? I still think that your temperature gauge reading about 1/3 is a more 'healthy' cooling system vs. reading 1/2. Was it reading near 1/2 when the car was new? If it routinely runs at 1/2 or higher, that's when you should be worried.

My Hondas read about 1/3 scale when driving. Running the engine while parked, stuck in traffic, or if you block off the radiator, it should climb up to 'around' 1/2, then the electric fan comes on. The setpoint for the fan is higher so it doesn't keep running all the time.

It gets hot in Ga, right? (OK, I'm a good wizard so I already know the answer...) I think around August your engine will be happy if you leave it like it is. Running this little bit cooler should be better for the engine's lifespan.

 

I guess your right again wizard. Thanks for the info.