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  1. #1
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    Member No: 97719 ncamie is an unknown quantity at this point ncamie's Avatar
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    Thermostat Question and other Coolant Relateds

    I've been trying to diagnose a cooling problem for the past couple of weeks (you can see the thread under "thermostat sensors" below). Well, thank goodness I found a used coolant level sensor at the local junkyard. Cost me one dollar! Works like a charm and now I'm sure I'm not loosing any coolant to a leak. Incidentally, I've gone through 2 new sensors from BavAuto with with no luck. I opened up the BavAuto sensor and found it had blown up inside. Literally the guts of it were mush. Weird! After careful inspection I found out that a small o-ring was missing from the new sensor and that must have allowed hot coolant into the guts to cook em. The ole dollar special has this o-ring and i'm loving it.

    Now back to the cooling problem. On every drive my temperature gauge in the instrument cluster creeps right up to redline after about a 20-25 minute drive on the highway. Never any boil overs or other apparent driving problems of any sort.

    Yesterday I shut down the car after a drive, opened the hood, and touch inspected my coolant hoses coming and going from the radiator. They were nicely pressurized. What I found odd was that the hose coming from the engine into the radiator (top hose) was hot, very hot. The lower hose going to the water pump was stone cold. I don't mean warm, or tepid, or anything like that. I mean right down cold like a glass of iced tea! Is this normal? Shouldn't that hose be warm at least?

    I know how this system works thermodynamically. The radiator cools the hot water from the top hose and returns cooler water through the bottom hose. Right? So logically it would make sense that the way things indicate everything is all right. But the cold of that hose is tooooooo toooooooo coooold; even here in Charlotte's freezing temperatures the hose should be warm.

    A couple of weeks ago I removed and visually inspected the radiator and water pump. Both seemed okay. Tell me something else. If the radiator had blockage wouldn't the lower (return) hose be just as hot as the top hose; or at least close to it? Could my thermostat be the culprit? I don't know because I have "boil cook" tested it in a pan. Seemingly worked fine.

    This is all just a mystery to me now.



  2. #2
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    Member No: 13623 tcachtung is an unknown quantity at this point tcachtung's Avatar
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    Could be a stuck thermostat, bad water pump......

    clogged radiator, aux fan....etc, etc. You have deeper issues than a low coolant issue. Suggest you get a Bentley manual for your vehicle and start from the beginning in the cooling system. Or try www.bimrs.org for a qualified indy. Trent Cole, Tech Advisor, Lone Star Chapter, BMW CCA
    President, Lone Star Bavarian, Inc.
    FT. Worth Tx, 76132
    www.lonestarbavarian.com

  3. #3
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    Re: Could be a stuck thermostat, bad water pump......

    Not to sound condesending but of course it's not a coolant level sender. I implied that in the post. I do appreciate the certified garage references but I simply cannot afford a shop to work on my car right now. I have to do it with roadfly's membership help. Thanks though.

  4. #4
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    Your general discussion is correct.


  5. #5
    Matt Hernandez
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    the the hoses off and clean out the radiator

    if that doesnt free up a potential clog, then replace the water pump, thermostat is a cheap 5 dollar replacement with the o ring.
    make sure to bleed the air from the cooling system whenever letting air in....

  6. #6
    Joe in NJ
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    Re: Could be a stuck thermostat, bad water pump......

    MY 2 cents...

    On a 20 year old car, do NOT trust the coolant temp gauge on your dash!

    Mine fluctuates up and down and when I tap the dash window it goes back to normal. The gauges are unreliable

  7. #7
    ray7er6er5er
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    Probably a faulty thermostat. What car?


  8. #8
    ray7er6er5er
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    PS...be sure and get the right one. Some thermo

    stats are backwards, with the flange on the wrong side...and won't work.

  9. #9
    Norman
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    Re: PS...be sure and get the right one. Some thermo

    Thanks. I've checked the thermostat. The spring is facing the rear of the car with the arrow up. Even though this thermostat is relatively new, I'm thinking of replacing it. I've heard of too many other guys here with faulty new thermostats. Can a new one from the corner auto parts store be good enough?

  10. #10
    Norman
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    Re: Could be a stuck thermostat, bad water pump......

    Yeah I've thought of that. Hmmmm. I wouldn't mind if it did but I just need to make sure that the engine is in fact not overheating. I never have boil overs or anything else. Just a bouncing gauge. Even my radiator auxiliary fan doesn't come on but this could be due to faulty sensors. Like I said, Hmmmmm.

    <a href="http://picasaweb.google.com/Norman.Camamile/MyPictures02/photo#5160200583753280402"><img src="http://lh4.google.com/Norman.Camamile/R5y3F0xgq5I/AAAAAAAAAIg/QsgtAqEF0-o/s144/IMG_2036.jpg" /></a>

  11. #11
    ray7er6er5er
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    IMHO call Steve Haygood with your vin # to be

    sure, he'll give you the right one.

  12. #12
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    Member No: 97719 ncamie is an unknown quantity at this point ncamie's Avatar
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    Sorry guys. This is all about my '88 535is...

    I was thinking...Is there a way to check the temperature of the coolant without using the instrument cluster gauges inside the car? Some kind of jerry rig set up? This way I can be SURE of what the coolant temperature is really doing.
    <a href="http://picasaweb.google.com/Norman.Camamile/MyPictures02/photo#5160200583753280402"><img src="http://lh4.google.com/Norman.Camamile/R5y3F0xgq5I/AAAAAAAAAIg/QsgtAqEF0-o/s400/IMG_2036.jpg" /></a>

  13. #13
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    Member No: 75402 m735is is an unknown quantity at this point m735is's Avatar
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    I installed VDO gauges-

    with all of the temp gauge problems I was having on my e23, I figured I would install it for a back up.

    I quickly installed one on my e32 to double check that cars readings also. I just have to come up with a good place to mount it permanently.

    Or you could use a thermometer of some sort-either an infrared or an old school one.Steve B
    4/85 e23 735i (summer/fall use)
    1/88 e32 735i (winter/spring use)
    6/88 e32 735iL (long term project)

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