Hello everyone!
I drive a 1993 Honda Civc LX with a 1.6 fL engine. I am noticing some recent and alarming developments in my engine that I have been unable to resolve, and I'm hoping you may have some input to point me in the right direction.

Firstly, I notice that my engine heats to operating temperature very quickly (within a mile of starting the car, which is faster than I am used to seeing) and when idling for more than about a minute or two the engine temp start to crawl up but goes back down quickly as soon as I start moving again.
The other thing I'm noticing, and I'm including it in this post because I'm not sure if it's related to the above, is that my exhaust smells strongly of gasoline especially when I first start the car.

In regard to the first thing; I have checked the coolant secondary reservoir to see if maybe the problem was having low coolant, but the reservoir is actually slightly above the max line. I have not tested the fan motor nor the little computer that tells it when to start/stop (the black box like one that is directly connected to the motor cables - I forget what it's called).

In reading my owners repair manual I found that the problem may be with the engine temperature sensor (though I''m not sure which sensor it means, the coolant sensor or the thermostat) being tuck in the "close" position and trying to heat my engine as though the block were cold at all times. It seems - at least at time of reading - that this could account for the gas smell and the engine temp fluctuation both, but I'm not sure that these two things are so related.

I also checked my coolant hoses, and they are all the same temperature and are all appropriately warm to the touch when the engine has heated to operating temperature. None of them appear to be evacuated (in that they aren't 'squished' or devoid of coolant fluid) so it appears coolant is flowing regularly during normal driving.

Has anyone experienced this problem before, and if so do you have any advice as to what the problem may be or other ways to get a diagnosis?
Any help would be greatly appreciated

 

Check coolant in the radiator too, not just the reservoir. Radiator should stay full to the top. Never take the radiator cap off unless the engine is cold.

The fan is controlled by a thermal switch on the thermostat housing (where the lower radiator hose meets the engine near the starter). If you only experience overheating when the car is sitting still, it is probably that. Unplug the switch and jumper the wires in the plug on the car side. The fan should now start immediately when you turn the key on. Test drive with fan running constantly and confirm no overheating. If the fan doesn't start with the switch jumpered, check the motor, fuse, and relay. The fuse and relay are in the fuse box near the battery.

The gas smell, if it is something abnormal, is not going to be related to the cooling system.

 

I checked my radiator. By 'full to the top' do you mean right up to the radiator cap? If so (and this may be a stupid questions, but I'm not very familiar with cooling systems) would I have to worry about pressure buildup when the engine heats if the radiator is full to the top when cold? Or would siphoning some of the reservoir solve that problem by freeing up some spillover room? In any case, I could see the first layer of metal inside the radiator so I highly doubt it is anywhere near the full mark.

Thank you for your input on the coolant issue, I will have the radiator refilled tomorrow when I get my oil changed (they'll fill it for free!) and have them check to see if I should get the cooling system serviced (via a cooling system flush) to give the system a little longevity.

As for the gas smell, it is indeed unusual but I also put in a new starter very recently, so perhaps that has something to do with it. I'll do some more homework on it and see what I find out.

Thanks again for the help, I appreciate it

 

That is the problem (or at least a symptom resulting from another problem), the coolant in the radiator should be right up to the neck. You should not see metal.

The way it is supposed to work, as the engine heats up to normal temperature, the pressure rises until it overcomes the spring on the cap and lifts the seal plate. Then the coolant pushes out of the radiator and flows through the small hose into the reservoir. As the engine cools down, the process reverses (there is a check valve in the center of the seal plate on the cap). So the radiator and the engine always stay completely full with no air pockets at all.

 

I had guess about the pressure thing, but I was unaware that any air at all in the res is a bad sign, as I seem to have underestimated the function of the secondary reservoir. Ill get this fixed pronto then, and thank you for getting me learned in proper radiator function, it's always been a grey area of understanding for me.