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  • Temp issues. Possible overheating.

    Will an air bubble or pocket surrounding an aftermarket temp sender cause higher than actual water temp readings?
    Jim Schumacher
    My 240

  • #2
    No, but air bubbles going through the motor will cause water temps to spike up since you have no coolant taking the heat away for a second.

    Air in the system will cause it to just plain run hotter though, as you have parts of the engine not actually cooled by coolant.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
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    • #3
      Thanks Def. That wasn't what I wanted to hear at least my understanding of your explanation. Heres my issue: My Omori gauge reads much higher than the PFC commander which gets its reading from the factory temp sender and controls the operation of the electric fans. But, my Omori gauge is usually what I use to keep an eye on temps as I rarely use the Commander. Today all of sudden the Omori gauge reads real hot but the fans haven't kicked on because the PFC was reading temps well below. I'm thinking I wasn't actually running hot (cool day and easy driving) but maybe my sensor went bad? or, I was hoping, it's exposed to air bubbles or an air pocket.
      Jim Schumacher
      My 240

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      • #4
        Guess the Omori gauge is in the upper radiator hose? It'll naturally read a bit hotter than the factory temp sensor.

        What were the temps in question?
        '18 Chevrolet Volt - Electric fun hatch for DD duty!


        DefSport Koni Sleeve and Spring Perch Buy!!!
        http://www.nissanroadracing.com/showthread.php?t=5902

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        • #5
          Originally posted by Def View Post
          Guess the Omori gauge is in the upper radiator hose? It'll naturally read a bit hotter than the factory temp sensor.

          What were the temps in question?
          It is in the upper water neck. When the Omori unit was reading 240 degrees I stopped, popped the hood and the fans wern't running. I hadn't thought to look at the Commander at the time but I can almost guarantee it was reading well below it's fan on cycle as it was a cool day and I was driving real easy. I suspect that is why the fans weren't running and I suspect I wasn't actually seeing water temps of 240 degrees. Could air in the system possibly cause this?

          I'd let the car run until the Commander temp reading kicked on the fans but am reluctant to do so because the Omori unit would probably be reading upwards of 270 degrees and I got nervous not knowing the real culprit.
          Jim Schumacher
          My 240

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          • #6
            Hmmm... does coolant come out when you open the bleeder screw/bolt? Is it filled up to the top of the radiator?
            '18 Chevrolet Volt - Electric fun hatch for DD duty!


            DefSport Koni Sleeve and Spring Perch Buy!!!
            http://www.nissanroadracing.com/showthread.php?t=5902

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            • #7
              Jim, for what it's worth, my Pivot fan controller always reads 5-7 degrees C higher than my PowerFC commander, and they BOTH read from the factory water temp sender. Not sure what that translates to in Fahrenheit but I know it's a significant difference.

              I would check the coolant level, but I suspect the sender for your Omori may have a problem, and isn't reading correctly.
              1990 S13, SR-swapped "Budget Baller" - gone down the road...

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              • #8
                I doubt this is happening, but when the temp sensor was on its way out in my truck, it caused the thing to read lower than actual temp.

                The symptom for that in my case was the truck running rich, since it was an old TBI setup.. As it thought the engine was colder, it ran richer and richer. then the sensor failed, the truck wouldn't run anymore. soon as you crank the engine, it would run the injectors wide open and flood the engine. DOH!!

                Anyway I doubt that's the case here. as has been suggested, you might try to bleed/burp the system and see if you can get any air out of it, then keep an eye on the temps.

                and yes, you'll also have quite a temp difference between what's going into and what's coming out of the engine- especially on colder days where the radiator is more effective.

                When I say that.. where does the factory temp sender read? Is it on the cold coolant side coming directly from the radiator?

                have you always noticed a large temp difference between the two gauges, or just not paid that close attention before. (my autometer gauge and my OBD-II reader show within about 5 deg of each other. autometer gauge is plugged into the factory dash gauge sender spot, right next to ECU temp sender).

                One more thing.. disconnect the senders for both and clean the connections. apply some dielectric grease when you put it back together and see if that causes a difference in the readings. it's possible that the connector is simply dirty.

                just throwing out ideas here, if you can't tell. maybe oneof them will help ya.
                Originally posted by SoSideways
                I don't care what color they are as long as they are LONG AND HARD.
                '04 G35 Sedan 6MT- The DD
                '96 240SX- The Track Toy

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                • #9
                  Originally posted by Def View Post
                  Hmmm... does coolant come out when you open the bleeder screw/bolt? Is it filled up to the top of the radiator?
                  Yes. I did a quick bleed and coolant does come out of the bleeder. And yes the radiator is full. I'm hoping I just need to give the system a good bleeding. I haven't really done so since flushing the system this spring. I'd just add fluid every day when the car cooled down till the raditaor is full.
                  Jim Schumacher
                  My 240

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                  • #10
                    Originally posted by Rittmeister View Post
                    Jim, for what it's worth, my Pivot fan controller always reads 5-7 degrees C higher than my PowerFC commander, and they BOTH read from the factory water temp sender. Not sure what that translates to in Fahrenheit but I know it's a significant difference.

                    I would check the coolant level, but I suspect the sender for your Omori may have a problem, and isn't reading correctly.
                    Thanks Ritt. I'm going to give it a good bleeding this afternoon and lather up the connectors with dielectric grease as matt suggested. Hope this combination of tasks solves the problem.
                    Jim Schumacher
                    My 240

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                    • #11
                      Originally posted by Matt93SE View Post
                      have you always noticed a large temp difference between the two gauges, or just not paid that close attention before.
                      I never really paid attention but suspected the readings were close because the fans would kick on when the Ormori gauge read about 210 which is the temp the fans are supposed to kick on, right?
                      Jim Schumacher
                      My 240

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                      • #12
                        One thing mentioned in the FSM for the maxima is that you have to jack the front end of the car about 3' in the air to get all the air out of the system. there's high spots in the block and coolant lines and crap like that that will retain air unless you jack the car up.

                        (or worse yet- the newer maximas require use of a vacuum pump attached to the system to suck coolant into all the little passages!)

                        also remember to turn your heater on while you're doing it. there's high spots where air can gather in the heater hoses and in the core.
                        Originally posted by SoSideways
                        I don't care what color they are as long as they are LONG AND HARD.
                        '04 G35 Sedan 6MT- The DD
                        '96 240SX- The Track Toy

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                        • #13
                          Originally posted by shoes59 View Post
                          I never really paid attention but suspected the readings were close because the fans would kick on when the Ormori gauge read about 210 which is the temp the fans are supposed to kick on, right?
                          Yeah. My fans kick on when my autometer gauge reads about 210-ish. I have a 12" aftermarket fan (removed the mechanical one) hooked to the factory fan wiring so the ECU handles the thermostat job.
                          Originally posted by SoSideways
                          I don't care what color they are as long as they are LONG AND HARD.
                          '04 G35 Sedan 6MT- The DD
                          '96 240SX- The Track Toy

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                          • #14
                            read from my aem from factory i see a 10 degrees difference from factory sensor to the defi sensor that's mounted in the output port.

                            Most PM answers: F 17X9 +22, R 17X9 +35

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                            • #15
                              Originally posted by Your Mom View Post
                              read from my aem from factory i see a 10 degrees difference from factory sensor to the defi sensor that's mounted in the output port.
                              After a thorough bleeding and some dielectric grease the temp on both gauges now remain static. My Omori gauge reads 170 degrees F, my Commander reads 65 degeree C which is about a 20 degree F difference. I suspect I never really had an overheating issue but rather air in the system and possibly a faulty Omori sensor. Thanks to all who chimed in. I'm going to bleed the system again for good measure while my heater is one as Matt suggested.
                              Jim Schumacher
                              My 240

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