Temperature gauge is not staying one place on highway speed

FARHAN2149

MEMBER
2006 NISSAN MAXIMA
3.0L
6 CYL
2WD
AUTOMATIC
160,000 MILES

On highway driving if my rpm is below 2 the temperature gauge stays at one place, but if I am driving 100 kmph and the rpm is above 2 then temperature gauge is fluctuating slightly up stay there for some time and then coming down, and on 100 kmph I pump hard acceleration the temperature immediately go down to normal position. What can cause this problem?
I changed twice thermostat, I changed radiator cap also. I change coolant, also bled properly. My heater also work good. By gun I checked the temperature of hose they are as they should b upper is very hot and lower is 15 degrees below now I think it is water pump. But I am confused because there is no sign of leaking or any squeaking sound. The engine is very silent and the both fans work as they should be.

1 Reply

STEVE W.

MECHANIC
13,445 POSTS

I would check the connector on the engine coolant sensor. It sounds like it may have some corrosion in it or the connector pins are slightly loose causing a poor connection. When you hit the throttle and the engine move the connection shifts. I would also check the engine to chassis and battery to engine ground straps. If one of those was corroded or failing a poor ground could cause gauges to act the same way.