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2006 F250 Overheat alarm while gauge showing normal operating temperature

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  • 2006 F250 Overheat alarm while gauge showing normal operating temperature

    2006 F250TUR overheating issues 816 hours. Sorry for the long post, but I want to provide as many details as I can, as I have been chasing this for 6 months now. Had some intermittent overheating issues last summer. Tell tale showing a steady stream while running and while attached to flush adapter. Replaced water pump/wear plate and housing, as well as the PRV. Ran and still overheating while at speed, OK at idle and off plane speeds. Found that I had the exhaust stack corrosion so replaced entire mid section, plus oil pump and speedy sleeve since I was there. (pic of corrosion attached) Fired it up on muffs and found that I was not getting water out of tell tale, put tape over lower intake same thing. Hooked up hose to flush adapter and same thing, no water from tell tale. Went through entire cooling system (external lines) with compressed air, all of the lines are free. Thermostats cleaned and checked, which have about 70 hours since they were replaced. Found if I ran water thru up tube and flush adapter at same time I could get water out of tell tale. Pulled the 4 large zincs from the back of the heads and found a bunch of salt debris in the motor, cleaned out as much as possible. Ran a solution of Barnacle Buster (Phosphoric acid) thru motor with a submersible pump in a catch basin for 4 hours thru the up tube and the flush adapter, and got a ton of junk out of the motor. At this point the only way I can get water out of the tell tale is still to pump water up the up tube AND into the flush adapter at the same time, which I did for another 4 hours to get all of the acid out of the motor. Replaced large zincs in the heads, the passages are now nice and clean. Pulled the exhaust plates from back of motor and found a 2 inch long piece of an o-ring stuck in a water passage between the outer and inner exhaust plate, possibly my culprit! My guess it was from an old water pump housing that lost an o-ring previous to my owning the motor. Water passages looking into the back of the motor also look nice and clean. I also realized at this point that the PRV that came with the new exhaust kit looked different than the one I had installed just previous to discovering the midsection corrosion. I put the other "new" PRV back in in the motor. Pic attached, original on left, middle is one that I just put back in, right is one that came with exhaust kit. New one has holes all of the way around it, vs. two at 12:00 and two at 6:00. Put exhaust plates back on with new gaskets and new zincs yesterday, reinstalled lower unit and attached a hose to the flush adapter and water came out of tell tale as it should! At this point I am dancing!!! Put muffs on the lower unit, fire up the engine and tell tale is streaming normally. Don't know if it was the piece of O-ring or the swapped PRV, but again..as happy as can be. Until....... Overheat alarm sounds. I am looking at gauge and the temp is reading in the normal range, yet alarm is going sounding. (Pics attached) Neither head feels overly hot to the hand, water from tell tale is not overly hot. What am I missing here...a faulty sensor? What do I do next. I know there are a few temp sensors, but not sure which one(s) trigger the alarm and which one(s) feed the temp gauge. Thanks in advance for any help!!!
    Left to Right Old, New, New with Exhaust Kit Gauge showing middle temp 1 second before overheat alarm Overheat on display while temp in middle normal range

  • #2
    Do you have proper service manual? If not, go here to get it.

    https://www.vansoutboardparts.com/se...ervice-manuals

    Comment


    • #3
      I do have the Yamaha service manual

      Comment


      • #4
        Should tell you what temp sensors do what and how to test? Have you done that?

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        • #5
          the temp value comes from a sensor that is set into the block,
          port side between the thermostat and the crankshaft

          set into each of the thermostat covers is a temp switch

          the logic the ECU uses to throw a flag confuses me;

          it may be possible to get an alarm w/ "normal" temp value but one overheated thermo switch

          as Panasonic suggest, you can test the switches and the sensor to see if they are in range.

          Comment


          • #6
            BTW I'm disappointed that after all the work you've gone on the engine and specifically the cooling system,

            its not clear that the temperature of the telltale water has no relevance to the temp of the engine itself.


            perhaps also worth noting that "overheating on the muffs" is hardly unusual with large Yamahas...

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            • #7

              "set into each of the thermostat cover is a temp switch" is a good clue to me as you said you were in there fooling with the thermostats....

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              • #8
                are you sure it is an over temp alarm? Yamaha uses the same tone for most all the alarms.
                have you actually checked with YDS if one of the temp switch's are closed or the water detect on?

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                • #9
                  Command link gauge reads "Overheat" overheat, plus the audible alarm. Have YDS, but cant get the dang thing to connect to my laptop for some reason. Will try that again today. Going to check the Engine Temp Sensor and thermoswitch today per the Manual and see if they are in spec.... will update..

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                  • #10
                    Update....Got YDS to connect to motor finally. Engine is showing operating temperature of 157 degrees at idle after warmed up, which shows in the middle of temp range on the Command Link gauge. At this temperature the termoswitch on the Starboard side gets triggered. Tested the thermoswitch, and it is operating within its parameters. Going to swap port and starboard thermostats to see if alarm gets triggered on the Port side of the engine. If so, will replace thermostats again, even though they have only about 70 hours on them. If warning still on Starboard side, suspect a blockage in that side of motor. Sound logical?

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                    • #11
                      can't hurt to try swapping thermostats, although easy enough to put them in a pan of water on the stove and confirm their performance -

                      as apparently you've done with the thermoswitch.

                      One interesting aspect of that V-motor is that the starboard head / thermostat housing is offset from the port - about 1-1 1/2" higher.

                      So if you have limited water volume being pumped into the block, its going to be able to exit the port head before it gets to exit the starboard head.

                      Comment


                      • #12
                        Originally posted by fairdeal View Post
                        the temp value comes from a sensor that is set into the block,
                        port side between the thermostat and the crankshaft

                        set into each of the thermostat covers is a temp switch

                        the logic the ECU uses to throw a flag confuses me;

                        it may be possible to get an alarm w/ "normal" temp value but one overheated thermo switch

                        as Panasonic suggest, you can test the switches and the sensor to see if they are in range.
                        What is the confusion?

                        Comment


                        • #13
                          I've forgotten the specifics -

                          but from the experimenting with the F225TXRD it appeared the ECU was programmed to disregard certain "implausible" inputs

                          IIRC closing the thermoswitch (perhaps even both - don't recall) with the thermosensor at a "cold" temperature did not trigger an alarm

                          and "faking" an excessive engine temperature but with thermoswitches open yielded a "check engine" alarm - not an overheat

                          so a bit more complicated than simple switching

                          Comment


                          • #14
                            Originally posted by fairdeal View Post
                            I've forgotten the specifics -

                            but from the experimenting with the F225TXRD it appeared the ECU was programmed to disregard certain "implausible" inputs

                            IIRC closing the thermoswitch (perhaps even both - don't recall) with the thermosensor at a "cold" temperature did not trigger an alarm

                            and "faking" an excessive engine temperature but with thermoswitches open yielded a "check engine" alarm - not an overheat

                            so a bit more complicated than simple switching
                            I noticed something similar on my F150. Maybe three times I got a visual indicator of an oil pressure issue. No alarm. Shut the motor off each time. Restarted and continued on my way. Has not happened in several years.

                            No codes indicated on YDIS. Very unsettling though.

                            Comment


                            • #15
                              Originally posted by fairdeal View Post
                              I've forgotten the specifics -

                              but from the experimenting with the F225TXRD it appeared the ECU was programmed to disregard certain "implausible" inputs

                              IIRC closing the thermoswitch (perhaps even both - don't recall) with the thermosensor at a "cold" temperature did not trigger an alarm

                              and "faking" an excessive engine temperature but with thermoswitches open yielded a "check engine" alarm - not an overheat

                              so a bit more complicated than simple switching
                              What Yamaha has said about the criteria for the over temperature alarm being set is confusing, depending upon what document one is reading. No surprise there.

                              The alarm should sound:

                              A. when a thermoswitch closes and (1) 75 seconds time has elapsed since the motor was started or (2) 25 seconds time has elapsed since the motor has been running above 2000 RPM

                              B. when the engine temperature is above 248* F and 75 seconds time has elapsed since the motor was started or (2) 25 seconds time has elapsed since the motor has been running above 2000 RPM

                              Comment

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