So I have a 98 Honda Accord LX automatic and over the past few days I have had a strange thermostat issue. Several minutes after the car is started and left in idle the thermostat will slowly start to creep up, when I accelerate the thermostat will go down, the further I drive the quicker the change (goes up during idle faster, goes down when I accelerate faster. Now if I do the same thing while in park or neutral, same story, thermostat goes down. Also if I turn on the heater or cold air with or without the AC the thermostat goes down but not as much. No check engine lights during this process, radiator feels normal temp to touch, fluid level seems fine, don't see anything leaking under car, and it sounds like fan is turning on. I thought it might be the pump and the act of acceleration forces fluid through the system..any thoughts would be appreciated!!

Thanks

 

WELCOME TO FORUM -

when you speak of thermostat, seems like you're really describing the temp gauge movement you can see from the drivers seat.
That said, is there a problem? - you're just describing a sensor's motion ... is there a drive-ability issue?


if it's a sensor readout movement that's the problem, a new thermostat may resolve it, since I don't notice similar on my '93 or '97.

 

Most likely a faulty Engine Coolant Temp sensor.

You can confirm sensr by disconnecting the sensor (near and under distributor a single wire small sensor) to see if any movement occurs. It should stay flat (cold). Next try shorting the sensor to ground w/ keyswitch OFF and turning keyswitch briefly to On. It should rise rapidly, but turn OFF keyswitch before full scale is reached to avoid damaging gauge movement.

good luck