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Thread: Temp Questions

  1. #1
    Join Date
    Nov 2004
    Location
    Winston-Salem, NC
    Posts
    603

    Default Temp Questions

    Hey All,



    This past winter I discovered that my T-stat was stuck (or broken) in an always open position. But figured that summer was coming and it wouldn't hurt to have the stat wide-open when the air temps hit the mid-nineties, so I left it in (I know...stupid).

    Throughout the summer the temp needle has stayed at the 12 o'clock postion with no variance. But recently the needle is pegged one needle's width to the right of center (it must be getting more conservative ). Once the engine warms up the needle NEVER goes to 12 o'clock or below and now when coming off the highway it goes more towards the 3/4 mark. I also noticed this behavior on Monday in some stop and go traffic.

    My hoses look pretty new, I have the t-stat and o-rings and coolant to do the change.

    Questions:

    Could the T-stat have not been seated correctly and now it is?
    Is their anything else I should look at?
    What are the symptoms of a failing fan cluctch and how do I check it?
    Do I need to purchase and replace the T-stat housing gasket as well? (i have the al housing)

    If my fan clutch is failing, what are the advantages/disadvantages to changing to an electric fan and how difficult is the change (i.e. is it worth it?)

    Thanks!
    -ashley


    '92 525iA / 179k miles / Born 3.92 / ABS / No ASC / stock / North Carolina



    Paper Gaskets Suck!

  2. #2
    Join Date
    Jan 2004
    Posts
    4,150

    Default Sometimes when the thermostat breaks , it won't seal the

    bypass even though the outlet going to the radiator is open, with the bypass still open some of the coolant just bypasses without going through the radiator reducing the amount of cooling you get.. Thats the same reason that you don't want to remove the thermostat on a bmw and leave it out... This bottom pic will show how the coolant flows on a bmw thermostat





    Quote Originally Posted by acyre
    Hey All,



    This past winter I discovered that my T-stat was stuck (or broken) in an always open position. But figured that summer was coming and it wouldn't hurt to have the stat wide-open when the air temps hit the mid-nineties, so I left it in (I know...stupid).

    Throughout the summer the temp needle has stayed at the 12 o'clock postion with no variance. But recently the needle is pegged one needle's width to the right of center (it must be getting more conservative ). Once the engine warms up the needle NEVER goes to 12 o'clock or below and now when coming off the highway it goes more towards the 3/4 mark. I also noticed this behavior on Monday in some stop and go traffic.

    My hoses look pretty new, I have the t-stat and o-rings and coolant to do the change.

    Questions:

    Could the T-stat have not been seated correctly and now it is?
    Is their anything else I should look at?
    What are the symptoms of a failing fan cluctch and how do I check it?
    Do I need to purchase and replace the T-stat housing gasket as well? (i have the al housing)

    If my fan clutch is failing, what are the advantages/disadvantages to changing to an electric fan and how difficult is the change (i.e. is it worth it?)

    Thanks!
    -ashley

  3. #3
    Join Date
    Nov 2004
    Location
    Winston-Salem, NC
    Posts
    603

    Default

    [QUOTE=Bill R.]bypass even though the outlet going to the radiator is open, with the bypass still open some of the coolant just bypasses without going through the radiator reducing the amount of cooling you get.. Thats the same reason that you don't want to remove the thermostat on a bmw and leave it out... This bottom pic will show how the coolant flows on a bmw thermostat

    So Bill,

    If I understand you correctly, what you're saying is that the bypass is now open so that a larger amount (if not all) the coolant is going back into the engine instead of the radiator? If that's true than replacing the t-stat will fix this, yes?
    -ashley


    '92 525iA / 179k miles / Born 3.92 / ABS / No ASC / stock / North Carolina



    Paper Gaskets Suck!

  4. #4
    Join Date
    Jan 2004
    Posts
    4,150

    Default No, i'm saying that thats a possibility, but you won't know until you

    remove it to see.... Also your year very likely had the plastic impellar water pump which could also be a problem... But since you had a faulty thermostat in the winter i would start there as a likely starting point.




    [QUOTE=acyre]
    Quote Originally Posted by Bill R.
    bypass even though the outlet going to the radiator is open, with the bypass still open some of the coolant just bypasses without going through the radiator reducing the amount of cooling you get.. Thats the same reason that you don't want to remove the thermostat on a bmw and leave it out... This bottom pic will show how the coolant flows on a bmw thermostat

    So Bill,

    If I understand you correctly, what you're saying is that the bypass is now open so that a larger amount (if not all) the coolant is going back into the engine instead of the radiator? If that's true than replacing the t-stat will fix this, yes?
    -ashley

  5. #5
    Join Date
    Nov 2004
    Location
    Winston-Salem, NC
    Posts
    603

    Default

    Quote Originally Posted by Bill R.
    remove it to see.... Also your year very likely had the plastic impellar water pump which could also be a problem... But since you had a faulty thermostat in the winter i would start there as a likely starting point.
    Thanks Bill!

    I'm going to find time to change the T-stat (and the pump I guess) this week. Will I need a new gasket for the T-stat housing?
    -ashley


    '92 525iA / 179k miles / Born 3.92 / ABS / No ASC / stock / North Carolina



    Paper Gaskets Suck!

  6. #6
    Join Date
    Mar 2004
    Location
    So Cal
    Posts
    290

    Default gasket

    Quote Originally Posted by acyre
    Thanks Bill!

    I'm going to find time to change the T-stat (and the pump I guess) this week. Will I need a new gasket for the T-stat housing?
    -ashley
    The thermostat will come with a o-ring, but you will need the other little rubber gasket for the housing. Call BMA

    Greg Mendoza

  7. #7
    Join Date
    Jun 2005
    Location
    Davis, CA
    Posts
    48

    Default Symptoms of failing fan clutch are that the car runs

    cool on the highway but heats up at idle sitting at lights, etc. The fan clutch is designed to "lock up" when it gets hot increasing air flow through the radiator until it cools down then it begins to freewheel a little more using less engine hp. On the freeway air pushed through the radiator provides enough cooling that the fan clutch is mostly freewheeling. One not so scientific check is to get the car up to operating temp, let it sit and idle for a few minutes, open the hood then watch the fan when you turn the car off. Since the fan clutch should be hot enough to be locked up it should stop spinning almost immediately. If it spins for a while it is suspect for being bad.

    Do a search on mye28.com for how to test the fan clutch on an e28. I assume they are the same but you know what can happen when you ass u me.

    Quote Originally Posted by acyre
    Questions:

    Could the T-stat have not been seated correctly and now it is?
    Is their anything else I should look at?
    What are the symptoms of a failing fan cluctch and how do I check it?
    Do I need to purchase and replace the T-stat housing gasket as well? (i have the al housing)

    If my fan clutch is failing, what are the advantages/disadvantages to changing to an electric fan and how difficult is the change (i.e. is it worth it?)

    Thanks!
    -ashley
    Craig in Davis
    89 535i auto to manual conversion
    Delphin-Metallic/Black leather 296k
    83 533i 5 speed Alpinweiss/Cardinal Red leather 236k

  8. #8
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,843

    Default

    dont forget about the aux fans either.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  9. #9
    Join Date
    Jun 2005
    Location
    Davis, CA
    Posts
    48

    Default Good point about the aux fan. eom

    eom
    Quote Originally Posted by 632 Regal
    dont forget about the aux fans either.
    Craig in Davis
    89 535i auto to manual conversion
    Delphin-Metallic/Black leather 296k
    83 533i 5 speed Alpinweiss/Cardinal Red leather 236k

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