my radiator fan comes on all the time even when the engine isnt warmed up yet,
what could cause this... coolant temperature sender unit? temperature sensor? dirty coolant?

thanks

 

Bad radiator fan switch.
what are you using to tell you when the car is warmed up?
maybe the coolant flow isn't good and where the switch is gets hotter before the rest?
Many many possibilities.
all take time to diagnose.

 

I'll have a radiator for sale soon if you need one.

 

oh... it turns on and off a lot for short periods of time repeatedly

 

ok so check the switch and the relay

 

could also be a bad/dirty temp sensor connection.

it's the red sensor plugged into the coolant tube just between the throttle body and the crank angle sensor. pull that connector off and make sure it's clean and connecting well.

FYI, if you pull that connector off while the engine is running, the fans will come on because the ECU thinks the car is overheating. (this is a guess here from what I've seen, but) the ECU will also severely richen the fuel mixture and retard the timing to the point that when you plug the sensor back in, the engine will die if you don't open the throttle a little bit to feed it air.


but anyway, check that connector. it's quick and easy and free to fix if it's just dirty.

 

yep, mine died on me too after i cleaned the sensor and plugged it back in. i didn't know why though but now i do

 

that's just a guess at what the ECU does, but I'm sure it's something along those lines.
it alters timing and A/F based on engine load and temp. if the ECU thinks it's running really hot, it's going to turn on the rad fans and richen the mix to help cool it down.

 

i thought i screwed something up. the engine idled kind of rough for like 5 seconds and it cut off. started bck up after a few cranks.
silly question, but how can extra gas cool the engine down? won't the extra gas cause a bigger combustion?

 

not when there's too much fuel to burn. a leaner mix will cause the engine to knock and ping and run hotter. richening the mix past stoic will cool it down since there's more fuel than the air can burn. I can't explain how as it's been quite a while since I've read the theory on it, but I know it does. only drawback is that it can wreak havoc on a cat due to the heat in the exhaust.

also wouldn't surprise me if the engine did something with the EGR in cases like that.

 

even at correct air fuel mixture about a third of the gas is used for cooling purposes only and is not burned

 

ding ding ding!