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    Troubleshooting & Preventing Temperature Issue

    Model & Year: '89 325i coupe

    After 8+ years of enjoying a predictable warm up period (~5-8 minutes) and temperature reading (typically b/t 1st & 2nd marks), I noticed a change.

    Full warm up could take up to 20-25 minutes, and usually would only happen after driving for about 10 minutes on surface streets, then taking the freeway for while, and then getting off the freeway and going through typical stop and go traffic.

    At first, I thought this might be a fluke. After noticing that this was becoming standard, I began to suspect my t-stat might be partially stuck open. So I replaced it with a new 80 degree unit.

    Since then however, I notice that my typical idle at warm up sits around the half way mark (2nd mark) than between the 1st & 2nd marks as in the past. While driving, the temperature eventually returns to that position between 1st & 2nd marks, and while on the freeway always sits there (unless there's a slow down).

    At long lights, and when I take a while to get parked, the needle returns to the half way mark, and sometimes goes beyond by a small amount (which rarely happened before).

    Engine performance has remained consistent throughout, and even feels a little better after changing the t-stat.

    I'm now starting to think that I had two issues going on, and that I addressed only one of them when I changed the t-stat. I suspect the second issue is my fan clutch.

    I followed this troubleshooting guide, which seems pretty thorough.

    First, lets discuss what the fan clutch does and why it is there. The fan clutch is just what the name says, it is a mechanism that will clutch the fan on and off depending on the need for more or less cooling air to flow thru the radiator. It is a thermostatically controlled device that when opera


    My fan seems to have run consistently throughout the test (from initial start up), but was easily stopped by a rolled-up newspaper after full warm up (didn't even damage the paper). But the temp stayed pretty constant (b/t 1st & 2nd marks) once warmed up (I let the car run for about 15 minutes total). The last time I changed the fan clutch was about 7 years ago. Is it possible the clutch is in the early stages of failure?

    Anyway, I'd appreciate any thoughts on all of this. I have NOT overheated, but the needle does move more than I'm used to, and I get pretty uneasy when something on the car starts behaving differently after years of consistent performance.

    #2
    Your gauge readings sound very normal and you are on the right track. The fan will turn all the time but often only windmills rather than being driven so don't go by that. A rising idle temp is common but failing the newspaper does tell you its probably time for a new fan clutch.

    I'd also suggest taking an IR gun to your radiator. Amazing what a new one will do for cooling efficiency.
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      #3
      Failing the newspaper test when the engine is at operating temperature means a bad fan clutch. That will cause the temperature to rise when idling and at low road speed. At freeway speed there will enough airflow through the radiator to bring the temperature down.
      The car makes it possible, but the driver makes it happen.
      Jim Levie, Huntsville, AL

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