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    Engine running very cold

    It seems as if my engine is running 'too cold'... if there is such a thing. When it's cold (in the blue), it idles at about 2000 rpms to warm up. Keep in mind I have an M10 under the hood. In the morning (usually about 40 degrees F) it takes about 15 minutes of driving in order to warm the car up out of the blue on the temp gauge. If I proceed to drive on the freeway after that the radiator cools the engine back down into the blue. I've recently replaced the coolant and the temp sensor. Could this be a problem with my thermostat?
    Originally posted by Gruelius
    and i do not know what bugg brakes are.

    #2
    I'd say its almost definitely the thermostat. Its probably stuck open and allowing coolant to flow through the radiator immediately after cold startup. You can grab the top radiator hose right after you start it cold and you shouldn't be able to feel any coolant flow.
    '91 318is
    sigpic

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      #3
      Originally posted by kencopperwheat
      Could this be a problem with my thermostat?
      I can't think of any other way the engine would run too cold. This happened to me as well. On my car, the thermostat broke into two pieces. Fun.

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        #4
        Originally posted by Brew
        I'd say its almost definitely the thermostat. Its probably stuck open and allowing coolant to flow through the radiator immediately after cold startup.
        That's exactly what I was thinking. I just wasn't sure how to test it.
        Originally posted by Gruelius
        and i do not know what bugg brakes are.

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          #5
          yeah your thermostat is stuck open


          Mike Fritz

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            #6
            Is there a way to change it without spilling a ton of coolant? I just changed mine.
            Originally posted by Gruelius
            and i do not know what bugg brakes are.

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              #7
              Could running cold cause my gas milage to drop significantly?
              Originally posted by Gruelius
              and i do not know what bugg brakes are.

              Comment


                #8
                Originally posted by kencopperwheat
                Could running cold cause my gas milage to drop significantly?
                Yes, at least in my case. Well, maybe not significantly, but my mileage improved when I swapped out my stuck-open thermostat. It would only climb up to barely 1/4 point when it should be fully warmed up, and like your car, took a long time to even get there.

                As far as coolant spillage goes, at least on the M42, I don't think there's a way to get the thermostat out without draining the coolant first.
                Yah it's kind of a hassle, but coolant is really cheap anyway, so you should give the thermostat/coolant change a go.
                ~ Go Canucks Go! ~

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                  #9
                  Originally posted by kencopperwheat
                  Could running cold cause my gas milage to drop significantly?
                  Yes, the car is designed to run efficient when it is at normal operating temperature. You can possibly be in open loop which would cause the car to tun rich. Your car spits out more emissions in 30 seconds after startup than it will in 30 minutes when warm. (With a good convertor of course).

                  As for the coolant drain.. I'd just pluck the housing off and let it drain. Hopefully you wont loose too much. I've found if you drain the radiator a little bit (hoping to lower the level) it only causes twice the coolant to drain out.
                  Old and improved:

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                    #10
                    Originally posted by kencopperwheat
                    Is there a way to change it without spilling a ton of coolant? I just changed mine.
                    Just use a clean container and reuse the coolant.
                    '91 318is
                    sigpic

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                      #11
                      I think I remember reading somewhere that as long as the oil temperature is sufficient, the coolant temp can be pretty much anywhere it wants under the 1/2 mark. The only reason your thermostat is there is for heat.

                      At least I think I remember that right.

                      "See, we're adding a little something to this month's sales contest. As you all know, first prize is a Cadillac Eldorado. Anyone wanna see second prize? Second prize is a set of steak knives. Third prize is you're fired."

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                        #12
                        Originally posted by e30Matt
                        I think I remember reading somewhere that as long as the oil temperature is sufficient, the coolant temp can be pretty much anywhere it wants under the 1/2 mark. The only reason your thermostat is there is for heat.

                        At least I think I remember that right.
                        That sounds about right, but i also think that the temp switch (that kicks motronic in/out of cold start - rich - mode) is linked to the water flow; if its not hot enough the car may be running in cold mode all the time

                        i'd bet $10 its the thermostat, same happened when i bought my car... it wouldnt get past 1/4 and it would take forever to get there; a new tstat and i was good to go
                        Jay

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                          #13
                          I had a problem with running at 1/4 ont he gauge with my 90 325i. I took the thermostat out when replacing it wiith a higher temp thermo, and the thing was in two losely connected pieces. How does this happen?!?!

                          Anyway, I would assume that's youur problem.
                          - 2000 Audi S4 Stg 2 (sold)
                          - house (bought)
                          - 1997 Civic Hatch (shaky but driveable)
                          - 2010 Sportster 1200 Forty Eight Ed. (vroom)
                          - 1991 318is S50B30 (TBA)

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