I installed a new thermostat. Removed air bubbles. Let the car reach normal operating temperature. The car idled normally. Took the car for a drive. When I came to a stop and the car was in neutral the car almost died. Needle almost at zero rpms. I pulled the car back into my garage. I'm not sure what is causing this. I've done alot of reading on honda-tech and have seen other people mention a similar problem but it never seemed that the problem was resolved. Another piece of info, the top radiator hose and the radiator itself both became hot while the lower radiator hose remained cool to the touch. Thanks for any help.

Car is a 94 civic with b18c1 block, b16 head

 

thermostat aint opening. did it overheat?

 

It did not overheat. I don't think I allowed the car to run long enough. Any ideas as to why the thermostat would not open? Could this cause the very low idle?

 

You can't bleed the cooling system properly if coolant circulation is prevented by a stuck-closed thermostat or clogged radiator. Also be sure to turn the heater lever to max heat and open the bleeder bolt (if you have one) when bleeding the cooling system.

 

Your radiator could be plugged up.

 

that totally makes sense. but why would a brand new thermostat be stuck closed and how can i remedy the problem?

 

i forgot to mention that i have all new hoses and a new radiator. i guess a new radiator could be defective but i dont think that would cause the lower radiator hose to remain cool.

 

How did you bleed the cooling system? Does your engine have a bleeder bolt?

 

i dont know if what i did was technically bleeding the cooling system. i turned the car on with the radiator cap off and the heat turned on but the fan off. i dont have a bleeder bolt.

whether or not the system was bled properly, wouldnt the thermostat being stuck be the real problem? how can i fix a stuck (brand new) thermostat?

 

Air trapped in the cooling system could also block coolant flow. Park the car on an inclined driveway with the front end higher than the rear. Top off the coolant in the radiator and reservoir. Then repeat the bleeding process you mentioned until the radiator fan turns on twice.

 

I will try this tomorrow when I get off work.

I did not mention another detail which my be important, I apologize. My fan was set up to constantly run by the previous owner (wire from ignition to fan) and I was planning on figuring out why he did this but I haven't got around to it as of yet (didnt seem to be causing any problems). is there a certain amount of time that I should wait because obviously i cant wait for my fan to turn on twice if it is on constantlyl? second, could the fact that no coolant is flowing through lower hose cause the extremly low idle?

 

Generally the 2P connector to the radiator fan switch on the thermostat housing is jumped because the switch is bad. You may as well replace the switch so that the fan does not have to run all of the time.

The bleeding process for the cooling system can take 20 minutes or more.

Air trapped in the cooling system can discombobulate both the ECT sensor and the IACV, thereby leading to an unusually low idle speed.

 

thanks for your help. I will try what you suggested tomorrow. just making sure, the front should be higher than the rear?

 

Yes, having the front end higher than the rear will help release any air trapped in the cooling system.

 

are you using a honda thermostat, or a duralast type tstat from advance/autozone? from what i've read some people have experienced coolant problems after replacing there tstat with a non-oem part.

 

i have a duralast thermostat and i have overheating problem i might take it off and run it with out a thermo.

 

Running without a thermostat is not a good idea. Believe it or not, this can cause the engine to overheat.

 

so want could it be.

 

Listen to Ron. He knows what he's talking about like 1000000000%. I would imagine there is another existing problem due to the fact that the previous owner wired the fans up as such... Find out why.
Ron.. why does running without a thermostat cause overheating? just curious.

 

it is an OEM honda thermostat

 

i dont doubt there are additional problems at all. needless to say i made a poor choice in buying the car and have been fixing problems ever since.

 

its possible the thermostat is backwards. i almost put mine in wrong when i rebuilt my motor.

 

i believe i installed it correctly as i followed the helms guide instructions making sure the pin was facing up.

 

so what could it be?

 

so I did what RonJ@HT suggested. parked the car on an incline. luckily my driveway is pretty steep. i removed the radiator cap, turned the heater all the way up with the fan off and ran the car for over an hour. the entire time the engine temperature remained constant (the needle was less than halfway) and it idled around 700. as soon as i touched the gas pedal to take it for a drive, the idle dropped and the car stalled. any thoughts?