two coolant temp sensors?
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Champion
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two coolant temp sensors?
I was just thinkin my car still overheats and brand new temp sensor on the intake manifold. I was wondering if there was another alternate sensor on the radiator or sumthing? I really dont think it would be the ECU misreading temps cuz i reset several times and still doesnt work right and the fan kicks on,.. just a little too late. Any theories or anything else would be appreciated.
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RE: two coolant temp sensors?
SOHC? (guessing by the hood on your car) The temp sensor on the intake manifold is an air temp sensor. If you have a '96-up, it's combined with the MAP. The coolant temp sensor is located on the back side of the head. It's a two-part sensor - the accurate signal goes to your PCM, the guesstimate signal goes to the instrument cluster. If this doesn't solve your problem, start suspecting a small leak somewhere (head gasket included, but not as likely if you have the MLS gasket), or a failing water pump (less likely than the head gasket if it's less than 100k miles old).
Best of luck!
Best of luck!
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Champion
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RE: two coolant temp sensors?
I gotta DOHC r/t, .... sohc hood cuz its lighter... its got a new HG....its not leaking its just that fans dont kick on right away. I dont know where the sensor would be located do u have an illustration?
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RE: two coolant temp sensors?
Then yes, the sensor is on the intake manifold for DOHC's, over by/on the thermostat housing.
For fan control, there aren't many components. The sensor you've already replaced. The relays are up near the driver's side headlights on your car (I think), but those tend to be a go/no-go deal, not a work-when-I-feel-like-it deal. There's the PCM, which isn't a high failure rate item, then there's the wiring, which also tends to be go/no-go. If you have access to an OBD-2 scanner, you could get some readings and see when the events are happening. On my car, the fans came on ~220F and shut off ~200F (usualy coasted down to 195ish). The instrument cluster portion shot up instantly and dinged at 222F every time. Scanners can be had pretty cheap (I paid $80 or so for mine) and laptops/PDAs that are compatible you can get off ebay for $50 or so. Great diagnostic tool. I loved mine until it was stolen...
Bear with me here... Air is a very poor conductor of heat. If you have a leak and/or air trapped in the system, then when the fans kick on, they are trying to cool the air, not just the coolant, which could allow temps to keep rising. A leak will result in lower pressure, which means a lower boiling point. If the coolant boils, it forms steam. Steam isn't a good heat conductor either. Steam and air are compressible, so even without a leak, rising coolant temp would cause the coolant to expand, which would compress the bubble, not raise the pressure of the coolant. So again the boiling point is reduced, even without a leak. Also keep in mind that if that air/steam bubble gets around to the water pump, it doesn't pump very well... and the water pump bearing doesn't get cooled very well...
I'd recommend making sure that there is absolutely no air in the system. With the car cool and the reservoir halfway full, remove the rad cap and start the car. As the coolant heats up, it will expand (might overflow, so have some rags/bucket handy). Once the temp reaches 190-195F, the thermostat will open and coolant will start flowing. If level drops, there is air in the system. Add coolant while running. The thermostat will probably shut because the coolant you are adding is less than 195F... So you wait for it to open again and repeat. I wouldn't go more than 2 or 3 times, or the fans will kick on and make coolant temp drop again. Stop the car and immediately put the rad cap back on. Allow to cool for a while, and repeat. It usually takes me 3 tries after a coolant flush/fill before I'm satisfied with it. Helps if the front passenger corner is up a bit as well. I always use a new rad cap once I'm done.
Once that's all done and the car is cool again, note the level in the reservoir (sharpie works). Before driving every day, check the level. If it drops, you have a leak somewhere. My most recent leak took me almost a month to track down. Tiny pinhole where the core clamps to the end bell. That's all it takes.
Plugged radiator could be another option. I went through 3 rads in New England before finally getting an aluminum core (for less than a stock replacement!).
Best of luck!
For fan control, there aren't many components. The sensor you've already replaced. The relays are up near the driver's side headlights on your car (I think), but those tend to be a go/no-go deal, not a work-when-I-feel-like-it deal. There's the PCM, which isn't a high failure rate item, then there's the wiring, which also tends to be go/no-go. If you have access to an OBD-2 scanner, you could get some readings and see when the events are happening. On my car, the fans came on ~220F and shut off ~200F (usualy coasted down to 195ish). The instrument cluster portion shot up instantly and dinged at 222F every time. Scanners can be had pretty cheap (I paid $80 or so for mine) and laptops/PDAs that are compatible you can get off ebay for $50 or so. Great diagnostic tool. I loved mine until it was stolen...
Bear with me here... Air is a very poor conductor of heat. If you have a leak and/or air trapped in the system, then when the fans kick on, they are trying to cool the air, not just the coolant, which could allow temps to keep rising. A leak will result in lower pressure, which means a lower boiling point. If the coolant boils, it forms steam. Steam isn't a good heat conductor either. Steam and air are compressible, so even without a leak, rising coolant temp would cause the coolant to expand, which would compress the bubble, not raise the pressure of the coolant. So again the boiling point is reduced, even without a leak. Also keep in mind that if that air/steam bubble gets around to the water pump, it doesn't pump very well... and the water pump bearing doesn't get cooled very well...
I'd recommend making sure that there is absolutely no air in the system. With the car cool and the reservoir halfway full, remove the rad cap and start the car. As the coolant heats up, it will expand (might overflow, so have some rags/bucket handy). Once the temp reaches 190-195F, the thermostat will open and coolant will start flowing. If level drops, there is air in the system. Add coolant while running. The thermostat will probably shut because the coolant you are adding is less than 195F... So you wait for it to open again and repeat. I wouldn't go more than 2 or 3 times, or the fans will kick on and make coolant temp drop again. Stop the car and immediately put the rad cap back on. Allow to cool for a while, and repeat. It usually takes me 3 tries after a coolant flush/fill before I'm satisfied with it. Helps if the front passenger corner is up a bit as well. I always use a new rad cap once I'm done.
Once that's all done and the car is cool again, note the level in the reservoir (sharpie works). Before driving every day, check the level. If it drops, you have a leak somewhere. My most recent leak took me almost a month to track down. Tiny pinhole where the core clamps to the end bell. That's all it takes.
Plugged radiator could be another option. I went through 3 rads in New England before finally getting an aluminum core (for less than a stock replacement!).
Best of luck!