PA_Probe Posted February 9, 2007 Share Posted February 9, 2007 I have only had my 2.5i for a couple weeks now but one thing I noticed recently was that the temp gauge would drop during a 1 mile stretch of downhill driving every morning on my way to work. The needle stays right at the halfway point during normal driving like it should. But after coasting down this 1 mile stretch of road (even with the car in Drive) the needle would slowly drop a quarter way towards the cold. It gets about 1/8inch from the line down near the cold indicator. Then I get back on the gas and it returns to normal. Does anyone else have this happen on their 2.5i? My car has 26k miles on it at the moment and I am just wondering if its ready for a thermostat already. Link to comment Share on other sites More sharing options...
bosco Posted February 9, 2007 Share Posted February 9, 2007 welcome to the forum. i wouldn't worry about it. car has no load on it so temp would drop some as long as it warms up to operating temp and doesn't overheat your OK. btw where can you go down hill for a mile? Pa.? i forgot i'm a flatlander. bosco Stay Stock Stay Happy Link to comment Share on other sites More sharing options...
PA_Probe Posted February 9, 2007 Author Share Posted February 9, 2007 I just assumed that the drive belts on the motor would be turning the water pump, thus cycling the coolant and with the motor still firing that it would be generating the heat to keep the coolant up to temp. Any other vehicle I drive down that hill stays at its normal temp. I was just wondering if anyone else noticed the same thing. (BTW - Wopsy Mtn. and Buckhorn -daily commute driving to Altoona, PA) Link to comment Share on other sites More sharing options...
bosco Posted February 9, 2007 Share Posted February 9, 2007 I just assumed that the drive belts on the motor would be turning the water pump, thus cycling the coolant and with the motor still firing that it would be generating the heat to keep the coolant up to temp. Any other vehicle I drive down that hill stays at its normal temp. I was just wondering if anyone else noticed the same thing. (BTW - Wopsy Mtn. and Buckhorn -daily commute driving to Altoona, PA) remember that when going down hill for that mile you are pushing air across radiator and even though engine is running there is very little "load" on it going down hill. just a thought. bosco Stay Stock Stay Happy Link to comment Share on other sites More sharing options...
Vimy101 Posted February 9, 2007 Share Posted February 9, 2007 ^ I dunno. It sounds like a thermostat problem. The engine should maintain its temperature within the normal operating range. Link to comment Share on other sites More sharing options...
rc0032 Posted February 9, 2007 Share Posted February 9, 2007 It could be global warming Link to comment Share on other sites More sharing options...
vxracer Posted February 9, 2007 Share Posted February 9, 2007 My hypothesis is that nothing is wrong. These things are very efficient at idle; with aluminum block, heads, and radiator; going downhill with air flowing through radiator, in the winter in PA, probably with the heater on, is enough to cool the thing below thermostat temperature. This is the most ideal cooling situation that you can possibly get. Hence why arctic vehicles have shrouds for the radiator for extreme cold. Have you ever noticed tractor trailers up there with those "curtains" over their radiator? But I will never admit that I havent ever been wrong...I would just keep an eye on it. Link to comment Share on other sites More sharing options...
bosco Posted February 9, 2007 Share Posted February 9, 2007 ^ I dunno. It sounds like a thermostat problem. The engine should maintain its temperature within the normal operating range. then buy other t-stat and let the forum know the outcome. btw a minor fluctuation in the gauge reading doesn't mean the t-stat is bad. if t-stat was bad it probably wouldn't open at all (over heat) or if it stayed open in cold weather the car would more than likey not heat up or never reach operating temp. also check the coolant level. bosco try this in very cold weather get car to full operating temp then park it outside with a large fan in front of radiator idling. results? Stay Stock Stay Happy Link to comment Share on other sites More sharing options...
RyanE Posted February 9, 2007 Share Posted February 9, 2007 Also, how long does it take your car to warm up to the halfway point? I have a GT, so my car heats up pretty darn quick due to the turbo, but perhaps some 2.5i folks can give some data points as to the amount of time (and ambient temp) it takes their cars to warm up. If the thermostat was stuck open, it would indeed take a long time for the car to warm up, and also, the thermostat would not close when the coolant cooled (such as coasting down a long hill). This would result in your fluctuating temperatures. I have (in other brands) got no fewer than three defective brand-new thermostats, so it's possible yours was bad from the factory. Keep us posted! -Ryan Link to comment Share on other sites More sharing options...
ebpda9 Posted February 9, 2007 Share Posted February 9, 2007 i think it might be a bad thermostat. my car did that once or twice, but it does not do it regularily Link to comment Share on other sites More sharing options...
Vimy101 Posted February 9, 2007 Share Posted February 9, 2007 then buy other t-stat and let the forum know the outcome. btw a minor fluctuation in the gauge reading doesn't mean the t-stat is bad. if t-stat was bad it probably wouldn't open at all (over heat) or if it stayed open in cold weather the car would more than likey not heat up or never reach operating temp. also check the coolant level. bosco try this in very cold weather get car to full operating temp then park it outside with a large fan in front of radiator idling. results? I'm not having the problem with my thermostat. This could be a Subie/boxer specific phenomenom but unless I've been in extreme cold* (-30F) I've never seen a properly functioning theromstat be unable to maintain temperature. When the unit fails or is defective it might not open or close or might be slow to do either. * When I have been in really cold weather, I have blocked up the rad with cardboard in my previous cars. Link to comment Share on other sites More sharing options...
beatadrum Posted February 12, 2007 Share Posted February 12, 2007 I'm probally wrong, but there must be a sensor in there to read the oil temp right? so if your going downhill for an entire mile could the sensor be at the back of the tank and therefore not touching the sensor?? ...oh and the 2.5i warm up very quickly, mine takes about 2 minutes Link to comment Share on other sites More sharing options...
ebpda9 Posted February 12, 2007 Share Posted February 12, 2007 there should be a sensor that will measure the oil temp, but that is not going to the temp gauge. Link to comment Share on other sites More sharing options...
Vimy101 Posted February 12, 2007 Share Posted February 12, 2007 It could be global warming It could be a clever Subaru anti-GW device. Link to comment Share on other sites More sharing options...
beatadrum Posted February 12, 2007 Share Posted February 12, 2007 oops i kept thinking he was talking bout oil temp....sry, i wouldnt worry bout it, its not hurt you and if driving downhill for a mile is the only time then it should be fineh Link to comment Share on other sites More sharing options...
PA_Probe Posted February 13, 2007 Author Share Posted February 13, 2007 I'm probally wrong, but there must be a sensor in there to read the oil temp right? so if your going downhill for an entire mile could the sensor be at the back of the tank and therefore not touching the sensor?? ...oh and the 2.5i warm up very quickly, mine takes about 2 minutes At what temperature does it take only 2 minutes to warm up? I know mine takes more than 2 minutes at sub 30 degree temps. So maybe it is my T-Stat sticking open. Link to comment Share on other sites More sharing options...
GTS Jeff Posted February 17, 2007 Share Posted February 17, 2007 Why are you guys going on about the radiator? If the thermostat is functioning correctly, it should cut off flow to the rad as soon as temperatures start dropping. I would replace the tstat; they're cheap. AND MAKE SURE YOU BUY AN OEM TSTAT, AFTERMARKET ONES SUCK. Link to comment Share on other sites More sharing options...
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