Cooling Issues: overheating/wild temperature fluctuations

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  • zachhke
    Noobie
    • Aug 2011
    • 8
    #1

    Cooling Issues: overheating/wild temperature fluctuations

    I bought an 87 325is a few years back in pretty poor shape. It seems like no one had done any routine maintenance in years. I've slowly been getting it back into shape, and recently I replaced the timing belt and water pump as I had no idea the condition either were in. Before everything was replaced, the car would never overheat and would get up to temperature (a hair below the 1/2 way mark) and stay there. Now the car temperature wildly fluctuates depending on engine speed, swinging from just above the 1/4 way mark on the highway (stays there consistently when cruising at ~65) to starting to overheat in stop and go traffic. There are no more bubbles coming out of the bleeder valve when I open it so I think i've got all the air out of the system.



    Do any of y'all have any thoughts on where I went wrong or things I should check? Thanks!

    Zach
    Tags: None
    • mcr_driver
      R3V Elite
      • Mar 2009
      • 4491
      #2
      Have you been checking how much coolant you have lost or none at all, what is the condition of the coolant? Any headgasket work?

        Comment

        • zachhke
          Noobie
          • Aug 2011
          • 8
          #3
          Originally posted by mcr_driver
          Have you been checking how much coolant you have lost or none at all, what is the condition of the coolant? Any headgasket work?
          I'm not losing coolant, the reservoir is full, just shy of the mark from when I topped it off last during bleeding. I haven't done any headgasket work, and although I don't know the history on the car, it was cooling fine before I got in there (for the past ~2 years).

            Comment

            • jlevie
              R3V OG
              • Nov 2006
              • 13530
              #4
              My first thought would be a bad fan clutch, but a bad thermostat is also a possibility. Both are probably well overdue for replacement.
              The car makes it possible, but the driver makes it happen.
              Jim Levie, Huntsville, AL

                Comment

                • 603Racing
                  Mod Crazy
                  • Dec 2010
                  • 612
                  #5
                  Try the thermo first, they're pretty cheap. You may also want to take a tempurature reading manually to make sure that your temp gauge isn't on death's door. Odd that it reads on the cool side and that's what makes me think thermostat.
                  90 325i DD/Track
                  03 Durango 5.9


                  Originally posted by e30mpg
                  It is recommended to get new gasket but this is R3v and we just copper spray that shit......slap biotch on and tighten to tq.

                    Comment

                    • zachhke
                      Noobie
                      • Aug 2011
                      • 8
                      #6
                      Originally posted by jlevie
                      My first thought would be a bad fan clutch, but a bad thermostat is also a possibility. Both are probably well overdue for replacement.
                      Originally posted by 603Racing
                      Try the thermo first, they're pretty cheap. You may also want to take a tempurature reading manually to make sure that your temp gauge isn't on death's door. Odd that it reads on the cool side and that's what makes me think thermostat.
                      Thank you both, I'm going to try the thermostat today. It makes sense to me at least that if the thermostat is locked open I'd run cool on the highway and in stop and go traffic I'd overheat as the thermostat wouldn't be allowing time for the coolant to drop temp in the radiator. Hopefully at least...

                        Comment

                        • jlevie
                          R3V OG
                          • Nov 2006
                          • 13530
                          #7
                          A stuck open thermostat will cause the engine to run cold all the time. One that isn't opening all of the way could allow the engine to run hot when idling but not at speed. You can replace the thermostat, but the odds are that the fan clutch is also bad.
                          The car makes it possible, but the driver makes it happen.
                          Jim Levie, Huntsville, AL

                            Comment

                            • zachhke
                              Noobie
                              • Aug 2011
                              • 8
                              #8
                              Originally posted by jlevie
                              A stuck open thermostat will cause the engine to run cold all the time. One that isn't opening all of the way could allow the engine to run hot when idling but not at speed. You can replace the thermostat, but the odds are that the fan clutch is also bad.
                              Odds are you were right. I replaced the fan clutch after work today, and all is well. Thank you very much!

                                Comment

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