My car gets really warm at night when it gets cool outside. The temp will start to rise on the guage and I have to rev the motor to get the temp to go back down. The only thing I can think of here is that my thermostat is sticking closed and maybe reving the engine is causing enough pressure to kick the thermostat open again? Or could it be something else? On really hot days the car is fine, never overheats, its just at night during low engine loads that the temp starts to rise.

EDIT: I just realized how vague that was, by 'really warm' I mean that the temp needle actually goes above half way up the guage. At some points, if I let it, it will go about 70% up the guage and then slowly start to come back down to normal operating temperature (a little below the half way mark on the temp guage). I did a search on the forums but couldn't find anything that matched my symptoms.


Modified by 90crvtec at 2:34 PM 5/25/2005

 

It does sound like a stuck thermostat. A new one's not too expensive & that's easy to try.

 

OK, I'll replace the thermostat tonight and see what happens. I had also read that there was a coolent temp sensor? If this goes bad would it also present these symptoms?

I have a CRVTEC swap, so do I'd need to buy a thermostat for a B20B right?

 

Temp sensors are for measuring, they don't actually control temperature.

Look on the distributor-end of the head... Small one with 1-wire is the sender for the temperature gauge. If that wire is messed up, maybe this whole business is a wild-goose chase & the temperature isn't really overheating. (Don't count on this & ignore it...)

You know your VTEC oil-pressure switch with the green plug? There's a similar one nearby on the head. (Grey plug??) Thats's the temperature sensor for the ECU. Again, all it does is measure temperature, it doesn't tell the thermostat to open or close.

On the thermostat housing itself is another one with a 2-wire plug. That's the fan switch.

I guess your thermostat housing came from the CRV engine, so get a t-stat for a CRV. If they're any different???

Reading back thru your original post, does this happen while driving? If it never overheats while driving, then I'd look real hard at your fan controls. It's possible (I don't know) that your car's wiring is looking for TWO different fan switches & your (newer) engine only has one. Honda changed their control philosophy for radiator fans somewhere in early/mid '90s.

 

The overheating does happen while driving. If I let the car just warm up and site idle the radiator fan will usually come on but it takes a long time for this to happen. I usually have to go drive the car then come back and just let it idle, then the fan will kick on. Just for grins last night I pulled my radiator cap off of the radiator with the engine completely cold (had been sitting for over 8 hours). I start the car and let it warm up, I was never able to see the coolant in the radiator moving at all, even after the car had reached full temperature. Eventually I could see a little bit of steam coming off of the coolant at the top of the radiator fill hole. I noticed that my upper radiator hose was really really hot but my lower radiator hose was cool. This would lead me to believe that my thermostat was not opening.

I'll purchase a thermostat and a gasket for a CRV tonight and see what happens with it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 90crvtec &raquo;</TD></TR><TR><TD CLASS="quote">... This would lead me to believe that my thermostat was not opening.

I'll purchase a thermostat and a gasket for a CRV tonight and see what happens with it.</TD></TR></TABLE>Yeah.