1991 Honda civic temperature gage jumping?

Question

while driving down the road after the car has heated up and the temperature gage is in the normal position. the gage now moves up almost to the red sometimes over the red and back down to normal but not below. it moves quickly within a 15 min drive it will move up and down about 3 or 4 times with about 30 seconds almost or in the red with longer periods in the normal position. I listened to the engine and it sounds fine when this is happening no odd sounds. also emediatly after turning off the engine I have felt the engine and it feels fine. I do not think the car is over heating. the gage will move when traveling up hill or down and in nutral. rpms do not make a difference nor what gear the car is in. When the gage moves up it makes me really nurvious and I need to fix the problem for my sanity. my machinic has been unable to diagnose the problem. please help

Answer 1

Coolant doesn't change temperature that fast. It could be a bad sensor or wiring to it, or you could be low on coolant. If the coolant level drops below the point where the sensor is, you'll get wild fluctuations.

Answer 2

First, open the hood of this vehicle and remove the radiator cap.
Only do this when the engine is cold... otherwise you may burn
yourself. Next, look down into the radiator fill hole and check
the coolant level (use a flashlight if necessary). The coolant
should sufficiently cover the little metal "fins" inside the radiator.
If this is not the case, the coolant level is low.
NOTE: On most vehicles, you can also check the coolant level
simply by inspecting the coolant recovery tank. Refer to this
vehicle's owner's manual regarding this approach.

If its LOW

Let's examine this situation closely. First, the temperature
gauge reads hot ONLY in hot weather. OK, that's not such
a big deal... especially in stop-and-go traffic. But, the
gauge should go down as soon as the vehicle speeds up.
However, that's not case here because of the "at any speed"
part which implies that the gauge doesn't go down (or at
least doesn't go down much) when the vehicle speeds up.
This is the crux of the problem.
There are really only two things that can cause this. The
first is that the coolant level may be a little low. However,
this was ruled out. The other thing is that the radiator is
clogged/plugged up and therefore, even when you drive fast,
the air that "hits" the radiator isn't cooling the coolant. Put
another way, a radiator is most effective in cooling the
coolant (and thus the engine) when the vehicle is going fast.
Since the temperature gauge reads hot "at any speed", the
radiator must not be working well.

IF its High

Obviously, an engine's cooling system must have the right
amount of coolant to work efficiently. Since the coolant
level is low (as you indicated), this (likely) is the main cause
of this problem (the other possibility is a clogged radiator).
NOTE: AutoTech is guessing that the coolant level is only
slightly low. Why? Because, the temperature gauge reads
hot ONLY in hot weather. On the other hand, if the coolant
was extremely low, the temperature gauge would read hot
regardless of what the outside temperature was (unless of
course it was very, very cold outside).

Answer 3

First, open the hood of this motor vehicle and eliminate the radiator cap. only do this while the engine is chilly... or you may burn your self. next, look down into the radiator fill hollow and verify the coolant point (use a flashlight if mandatory). The coolant ought to sufficiently conceal the little metallic "fins" interior the radiator. If this isn't any longer the case, the coolant point is low. be conscious: On maximum vehicles, you additionally can verify the coolant point only with the help of analyzing the coolant restoration tank. verify with this motor vehicle's proprietor's handbook concerning this approach. If its LOW enable's examine this undertaking heavily. First, the temperature gauge reads warm only in warm climate. ok, this is not considered one of those enormous deal... enormously in end-and-flow site visitors. yet, the gauge ought to flow down as quickly because of the fact the motor vehicle hurries up. even regardless of the undeniable fact that, this is not case right here because of the "at any velocity" area which means that the gauge would not flow down (or a minimum of would not flow down a lot) while the motor vehicle hurries up. this is the crux of the undertaking. There are particularly only 2 issues that could reason this. the 1st is that the coolant point could be a splash low. even regardless of the undeniable fact that, this turn into ruled out. the different element is that the radiator is clogged/plugged up and hence, even once you force quickly, the air that "hits" the radiator isn't cooling the coolant. placed yet differently, a radiator is finest in cooling the coolant (and for this reason the engine) while the motor vehicle is going quickly. because of the fact the temperature gauge reads warm "at any velocity", the radiator should not be working properly. IF its severe for sure, an engine's cooling device ought to have the the superb option quantity of coolant to artwork effectively. because of the fact the coolant point is low (as you indicated), this (probable) is the main significant reason of this undertaking (the different threat is a clogged radiator). be conscious: AutoTech is guessing that the coolant point is only particularly low. Why? because of the fact, the temperature gauge reads warm only in warm climate. on the different hand, if the coolant turn into particularly low, the temperature gauge could study warm in spite of what the exterior temperature turn into (except of direction it turn into very, very chilly exterior).

Answer 4

could be the thermostat or the radiator fan or radiator fan relay.
ase tech