I have a 89 si w/a b20b , got the motor with 30,xxx miles on it. Car has a Pwr radiator , today the needle started acting weird. When I drive the car it wont come off the Cold mark , as soon as I come to a stop it starts to slowly move up , but then goes back down as I start moving, Car has a slim fan wired to a switch , I keep the fan off most of the time. Sound like a bad thermostat? Im not leaking coolant, The heat blows warm, I tried bleeding the system today and no change , Any ideas? Thanks

 

sounds like bad thermo

 

would I still have interior heat with a bad thermostat??

 

my car did the same thing recently change that thermostat

 

i have the same problem on my '94 tempo but i refuse to replace anything else on that piece of crap! i won't even change the oil more than once every 10,000 miles.

 

lol , thats funny. Anyone know If I would still have interior heat if the thermostat was stuck open? I do have heat even though the needle is reading Cold

 

better than at the H mark

I would reccomend new thermo, and yes you will have interior heat with a thermo reading cold...

 

mine fluctuates like this also and i have a nearly new gates thermostat with about 7k on it...as previously stated as long as the heat works and it doesn't overheat don't mess with it if it aint broke...!!!

 

thanks guys , guess im going to try an oem thermostat this weekend, cant think it would be anything else

 

I have been thinking , If the thermostat was stuck open wouldnt I have little or no heat coming from the vents?? I have heat even when the temp is reading cold...?

 

also my idle has been acting funny also??

 

this is driving me crazy , I got a new oem thermostat on the way

 

It would still blow warm air but it might not be as hot as it used to be if the thermostat is stuck open. It could be wiring to the coolant temp sensor or the sensor itself too.

 

I thought about the sensor but I got this motor with 30,000 miles on it from a jdm engine place, I was thinking maybe because the motor sat with no coolant in it that could have had something to do with the thermostat going bad?

 

That is very possible but the sensors can go bad. I bought my b18b with 30000 miles and it had a bad oil pressure sensor on it that i had to change. Check for a short in the wire as well since we do drive almost 30 year old cars. My 88 hatch has had so many stupid wiring problems that just popped up out of nowhere.

 

It wouldn't be your temp sensor, the temp sensor doesn't have anything to do with your temp gauge. It sends the info to your ecu. It would be the temp sending unit. Temp sensor has two wires going to it, and the sending unit has one. And if your heater is blowing hot air I would bet on the sending unit. If it was your thermostat the air would be noticeably cooler. And I wouldn't think it would fluctuate like that (in my experience). Good luck

 

the temp sensor is the one that plugs into the thermostat correct? Where is the temp sending unit located?