Hi there,

I have a 97 civic with a stick-shift, and in the last couple weeks, I've noticed after taking a long trip, about 1-2 hours or more, when I pull off the road and come to a stop, the temperature starts to spike up to about 2/3 to 3/4 up the indicator. However when I start driving, the indicator starts going down quite a bit, eventually back to normal. At about the same time, my overflow reservoir, which was initially just below the minimum level, is filled up to the top, with a little overflow.

I haven't noticed either the temp spike or the overflowed reservoir until the last 2 weeks. This started happening before I left on my now-current road-trip from CA to FL, and so far, as I write this in New Mexico, the car temperature hasn't risen or done anything unusual while driving--even in high heat, but without A/C (though I have A/C--trying to avoid the risk or possibility of overheating while driving). The last time it happened, while at a stoplight and seeing the temp needle go higher, I put on the heat full blast, which slowly lowered the temperature back to normal--and driving eventually helped it.

I got the car checked out by my trusted mechanic in CA before leaving to make sure there were no quirks in the cooling system, and so the thermostat was checked, radiator cap replaced, no leaks could be found anywhere, and the radiator seemed normal. And there seem to be no symptoms of a head gasket problem--performance seems normal, oil dipstick is just pure shiny oil, tailpipe doesn't smell sweet, etc--and it doesn't overheat when I drive, which it seems like it should if there were a head gasket problem.

So with all that said and all possible symptoms I can think of checking that have been checked--would anyone think of any possible causes for this? I'm thinking about getting it to another mechanic to get checked, but it'd be good to know what to look for first.

 

It's possible it is still the thermostat. Have your guy take it out put it in hotwater to see if it opens up properly. Depending on how old it is I would replace it anyway.

 

Does your fan come on at idle when the temp is "spiking"?

 

happen to me while back and turn out it was my temp sensor which cause my fan not turning on.. you can try bypass (jumper) on the switch so it would cool while driving to your destination

 

Thanks for the responses--I'll have to get the thermostat re-checked specifically, haven't been able to do that yet, and the last couple times the heat started spiking, I was blasting the fans on full heat, so it was kind of hard to tell if radiator fan was running. (Turning up the heat full blast helped to push down the engine temperature.) That said, I've noticed the radiator fan kick on before once, but only after the engine heat had spiked up a bit. I should also add, when I rev the engine a little bit, that seems to push down the temperature a little, also, so I have my doubts as to whether it'd just be a (radiator) fan issue.

 

Well so far, I've noticed at one point that when I came to a stop at a gas station, turned off the heat (just to cool down the engine, just in case) and let the engine idle; heat started to spike, and the radiator fan wasn't turning on like it should. Turning on the heat stopped it's spiking and slowly brought the temp back down.

That said, though, I got the cooling system rechecked by a mechanic recently, and after testing everything, they couldn't find any leaks or problems. I'm having the thermostat replaced anyway, so I'll have to see what that does. I might actually agree with cvcrcr99, that it might be a thermostat problem--if it sticks open (or closed?) it's possible that it's not letting enough coolant in, unless I (ironically) rev the engine higher, or start moving. Could that be possibly the case?

Anyway, I'll post back soon on the issue. Thanks again for the advice, all.

 

It can't be the thermostat. If it were, your temperature gauge would go past the halfway mark, even on the highway.
Obviously, if your fan isn't coming on, either the temperature switch or the fan is bad. Checking voltage at the fan will tell you if the switch is bad - no voltage at high temps = bad switch. If the switch is sending a control output voltage, then the fan connector or fan is bad. Most likely, it's the temperature switch that is bad.

 

If it is the switch, how does one come into possession of these, and would it be easy to fix? And where is it located?

 

I'd check with an auto parts store, first. If they don't have it, you can always get one at a dealership.

My service manual (for 96-97 Civics) shows the switch as being threaded into the thermostat cover (housing). It is sealed with an o-ring aganst the housing.

To test the "Engine Coolant Temperature Switch":
1. Remove when the coolant is cold to avoid spray-out.
2. Suspend the ECT switch in a container of water.
3. Heat the water and check its temperature with a thermometer.
4. Measure the resistance between the two switch connector terminals (A & B)
When the water temperature reaches 196-203 degrees F, the two terminals should be shorted (no resistance)
When the temperature drops 5-15 degrees F below the switched (high) temperature, the two terminals will disconnect (no longer be shorted)

If you can't run this test, simply buy a new ECT switch and make sure it has a new o-ring.

 

The thermostat housing is where the big hose from the bottom of the radiator meets the engine. Unplug the switch and use a small piece of bare wire to jumper the pins in the plug (on the harness side). The fan should now start immediately when you turn the key on. If it doesn't, check the motor, fuse, and relay. If it does, test drive like that with the fan running all the time and if it doesn't overheat, replace the switch.