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Thread: New guy has aux fan woes

  1. #1
    Join Date
    Aug 2005
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    Default New guy has aux fan woes

    Hi all. I'm new here, and new to BMW-dom.

    I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

    I'll save the story for another time and cut right to the chase.

    The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

    Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.

    Now, my questions:

    1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?

    2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.

    3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

    Any help is greatly appreciated. Thanks.

  2. #2
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    Default

    Quote Originally Posted by jaylebo
    Hi all. I'm new here, and new to BMW-dom.

    I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

    I'll save the story for another time and cut right to the chase.

    The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

    Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.

    Now, my questions:

    1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?

    2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.

    3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

    Any help is greatly appreciated. Thanks.
    Has the car had the newer style metal water pump installed?

    When was the last time the cars coolant was flushed?

    -Charles

  3. #3
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    Default

    Quote Originally Posted by dacoyote
    Has the car had the newer style metal water pump installed?
    Huh? Didn't know there was such a thing. How would I know?

    Quote Originally Posted by dacoyote
    When was the last time the cars coolant was flushed?
    Dunno exactly, although the thermostat was replaced last month. Would that have necessitated a coolant flush? The coolant looks a-ok.

    I should add that this problem surfaced about six months ago, and it's been sufacing again and again despite my mechanic's efforts. Since the aux fan does not work at all, I'm likely to suspect it as the cause of the problem. But what do I know?

    Thanks for the help.
    Last edited by Jay 535i; 08-04-2005 at 06:44 PM.

  4. #4
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    Default

    Quote Originally Posted by jaylebo
    Hi all. I'm new here, and new to BMW-dom.

    I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

    I'll save the story for another time and cut right to the chase.

    The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

    Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.

    Now, my questions:

    1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?

    2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.

    3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

    Any help is greatly appreciated. Thanks.
    First of all, the aux fan should come on when the temp gauge hit 3/4 or when the a/c goes on. Since the a/c doesn't work, does the gauge reach the 3/4 mark or higher when it overheats?

    Ralph Mendoza Jr. - Long Beach, CA

  5. #5
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    Default

    Quote Originally Posted by jaylebo
    Huh? Didn't know there was such a thing. How would I know?



    Dunno exactly, although the thermostat was replaced last month. Would that have necessitated a coolant flush? The coolant looks a-ok.

    I should add that this problem surfaced about six months ago, and it's been sufacing again and again despite my mechanic's efforts. Since the aux fan does not work at all, I'm likely to suspect it as the cause of the problem. But what do I know?

    Thanks for the help.
    If you have the PO's repair records, you know when the water pump was replaced.

    Does your car have a timing belt, which needs to be replaced at regular intervals 50,000-60,000 miles? If it has that belt and you don't have repair records I'd be worried about that. The good news is it's in the same area as the water pump and you can replace both at the same time.

    Ralph Mendoza Jr. - Long Beach, CA

  6. #6
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    Communist-wealth of Massachusetts
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    Default

    Quote Originally Posted by jaylebo
    Hi all. I'm new here, and new to BMW-dom.

    I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

    I'll save the story for another time and cut right to the chase.

    The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

    Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.
    Welcome!! Enjoy the new ride.

    [QUOTE=jaylebo]
    Now, my questions:

    1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?
    [/QUOTE}
    Yes, it is very possible. Also check the fuse box, if the resistor is bad the fuse is probably blown.

    Check the following link for more info:
    http://www.nmia.com/~dgnrg/page_20.htm

    Quote Originally Posted by jaylebo
    2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.
    Note likely. That sounds to me like the H2O pump may not be working properly. Only way to know for sure is to pull the pump. When is the last time your records indicate it was replaced? Most professionals are recommending replacement of the pump at 60K intervals now as a preventative measure.

    Quote Originally Posted by jaylebo
    3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

    Any help is greatly appreciated. Thanks.
    See the link above for everything you would ever want to know.

    Good Luck,
    Rory


    <Insert list of modifcations or clever saying here>

  7. #7
    Join Date
    Aug 2004
    Posts
    162

    Default Start with the fan clutch

    Hi,

    Aux fan aside, it sounds to me like your fan clutch needs replacement. This is the viscous coupling that drives the primary fan. These do fail pretty regularly and with the mileage and age you have, it's a pretty good bet it's time.

    Next step is to check the temperature sensors that control the aux fan. There should be two speeds, so check the wiring diagram. You can connect the fan directly to power to see if it comes on; this would confirm whether the fan itself is okay or not.

    Regards,
    Adnan

  8. #8
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    Default

    Thanks for all the replies. Here're the answeres to all the questions.

    Quote Originally Posted by uscharalph
    First of all, the aux fan should come on when the temp gauge hit 3/4 or when the a/c goes on. Since the a/c doesn't work, does the gauge reach the 3/4 mark or higher when it overheats?
    Oh yeah, it'll go into the red.

    Quote Originally Posted by uscharalph
    Does your car have a timing belt, which needs to be replaced at regular intervals 50,000-60,000 miles? If it has that belt and you don't have repair records I'd be worried about that. The good news is it's in the same area as the water pump and you can replace both at the same time.
    There is a belt, but I thought these cars had timing chains. There are no records, so I'd assume the worst. But I want to tackle the most likely culprits first, and since the aux fan isn't working it seems reasonable to start there. Doesn't it?

    As far as I can tell, all underhood fuses are okay. Haven't looked under the rear seats.

    Thanks for the tips, Rory. Water pump may not be that old. Unfortunately, my father wasn't the kind to keep records, but I have a vague recollection of him replacing that. His local mechanic is an honest and competent guy, but not a BMW specialist. That's why I'm inclinded to suspect that he totally overlooked the aux fan as a possible culprit, as it's damn near invisible to the uninitiated.

    Adnan, thanks. I've read a bit about the clutch fan in my search that brought me to this site, and I don't see any evidence of it needing replacing. The fan blows strong at all engine speeds. Can you recommend some sort of test?

    Quote Originally Posted by Adnan
    Next step is to check the temperature sensors that control the aux fan. There should be two speeds, so check the wiring diagram. You can connect the fan directly to power to see if it comes on; this would confirm whether the fan itself is okay or not.
    That's a little over my head. If you can describe exactly what to do, I'm sure I can do it, but I don't have a wiring diagram (yet -- Bentley is on the way), nor can I read one.

    Many thanks for all the help. Please keep it coming.

  9. #9
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    Default

    unless it's leaking or making a noise the pump is fine, m30s didn't have the plastic impeller, id bet whats happening is the bleeder line that goes from the left upper side of the radiator to the coolent tank is clogged somewhere, usually it's at the coolent tank end, when this line stops flowing the system can get airlocked
    all america wants is cold beer warm cat and a place to take a poop with a door on it

  10. #10
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    Oct 2004
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    Default

    Quote Originally Posted by jaylebo
    Huh? Didn't know there was such a thing. How would I know?



    Dunno exactly, although the thermostat was replaced last month. Would that have necessitated a coolant flush? The coolant looks a-ok.

    I should add that this problem surfaced about six months ago, and it's been sufacing again and again despite my mechanic's efforts. Since the aux fan does not work at all, I'm likely to suspect it as the cause of the problem. But what do I know?

    Thanks for the help.
    The M30 never came with a plastic water pump impeller, to my knowledge. All are metal.

    Who installed the thermostat? My guess is that the rubber O ring wasn't inserted correctly, and the tstat is stuck. The car may cool down below the 1/4 tick mark under way if this is the case. The rubber O ring goes behind the tstat in the housing, fitting right up against the thermostat cover. Here's a pic of how it orients on the tstat itself:



    ...where the end in the photo is the cover side. Correct fitment is necessary: the tstat housing coolant passages are altered depending on what the tstat is doing.

    best, whit

    EDIT: also note that the gasket shown in the picture isn't the O ring....the O ring should be installed, not the gasket.
    Last edited by Kalevera; 08-04-2005 at 08:17 PM.

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