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  1. #1
    Droz3
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    Water pump plastic impeller failure symptoms

    What are the usual symptoms of a water pump plastic impeller impending failure ?
    What will happen if the impellers breakdown while I drive, aside of the fact that the yemperature will raise very fast.
    If replaced by a dealer, does the dealer put back the same plastic impeller crap ?
    I have a 2001 3.0L with 43,000 miles. A growing whistle is coming from the front of my engine.
    Both belts, tensioners and alternator were replaced 5,000 miles ago.


  2. #2
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    You don't have to worry

    plastic impeller was not used after 1999. Does anyone else know different?

    But to answer your question, the primary symptom would be lots of steam from your radiator and the engine shutting down.

    And if the dealer replaced it and you DID have a plastic impeller they would use a metal one.

    You didn't mention whether the whistale was speed ependent or RPM dependent. If it is RPM dependent you should be able to hear it with the car stopped then you can localize it. If it is speed dependent then start looking for loose underbody parts.

    If it is RPM dependent pay particular attention to the fan, you could have a crack allowing one blade to whistle. Several have reported fan failures recently and the results are not pleasant

  3. #3
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    I've had 3 failures of the plastic impeller.

    None of them gave a warning. Car simply overheated in each case after the failure, and there was no evidence anything was wrong - other than, of course, the temparature gauge.

    When it happens, you'll probably be driving down the road and you will hear the "thump - thump" of your water as it begins to boil under pressure.

    If you have a weakness in your cooling system, it will be pronounced at this time. If not, you'll probably hear the boiling.

    Good luck.
    JByrd
    Z3 1.9
    Z3 2.8

    John Byrd's Solo 2 Autocross Site

  4. #4
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    Just before mine failed....

    For a few months before mine failed, the loose blades inside produced a metallic, knocking-like sound. In fact, on brisk acceleration, it fooled the knock sensor into retarding the ignition, making me lose power. At first I thought it was something wrong with the knock sensor or the Sharkware went bezerk. But we could find no electronic fault codes. Finally, like the others reported, the water pump failed. It was only after they replaced it that I figured out my "knock" problem, as the car no longer knocked after the repair and my engine was restored to full power.

    I fully agree with the recommendations of some magazines that people go ahead and change the pumps at 70-80,000 miles as a preventative measure. The alternative is getting stranded when you least expect it.Need4Spd
    Current: '01 M5/'05 M3 Conv. Past:'99 M Roadster/'95 M3

  5. #5
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    Member No: 40215 DaneKane is an unknown quantity at this point DaneKane's Avatar
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    ..last i heard it was back to "plastic"...for BMW

    ...supposedly the metal ones caused too many bearing failures...and plastic was reintroduced.. a better, stronger design and or material( possibly why so many metal ones are now on aftermarket?..food for thought anyho..) Cheers! dk '97 2.8 bg R

  6. #6
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    Re: ..last i heard it was back to

    Recently I asked the BMW dealership locally if they sold a metal blade impeller for the 98 2.8, and he said no they were plastic. Does that sound right?

  7. #7
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    my 2001 had plastic - better plastic

    it was some composite material
    new one was also same material
    BDOUGR Photos


  8. #8
    CraigAZ
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    You can find metal on the aftermerket.


  9. #9
    CraigAZ
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    Nice to know...

    I just (two months ago) installed an offical BMW part number pump with a cast metal impeller on my 97 2.8. FWIW the oldone had a built up metal impeller which surpised me. I needed to replace anyways since I saw signs of bearing failure behind the pump pulley...

  10. #10
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    would you describe it please..excruciating ..

    ...detail??(was impellor al or composite al+steel/al sheetmetal??)..inquiring mimes want to know...dk '97 2.8 bg R

  11. #11
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    Do you one better...here's a HUGE picture of it

    I was pretty surprised. I had never even heard mention of this and the replacement I had was a pretty roughly cast impeller. If I could have swapped the impellers I would have, this looked to have excellent flow characteristics.

    I can't really identify the aloys but it looks like bronze brazing to hold the pieces together. Almost hand made. And in case you are wondering it is now somewhere in a landfill in southern Arizona...



    download this picture, it is 2848x2136.

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    Thanks much amigo!...precision is not...

    ..overrated! Cheers! dk '97 2.8 bg R

  13. #13
    Bob S. Nor Cal
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    What linkage could there be between metal

    impellars and bearing failure. I wouldn't think thwere would be a difference unless there was a balance problem, which SHOULD not be the case..

    Just curious.

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    Have you seen anything like that before?

    It almost looked like a lab prototype to me. I couldn't imagine manufacturing that thing...

  15. #15
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    yes..it's the hp model that BMW deemed too..

    expensive to continue using(made in Germany)...the plastic impellor units were a lot cheaper(but problematic),the italien al units don't work as well,but don't implode,but do have bearing issues...and the new plastic ones still fail, but don't implode(but are cheaper)..so i guess i still like the hp(rare as it is)best..combined with fan delete(plus aux SPAL unit) could work out as best combo for al block equipped Z3's...Cheers! dk '97 2.8 bg R

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    Well, its bearing was weeping at 62K, se la vi...


  17. #17
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    ..i think it's more to do with Bmw's fan set-up...

    ..the fan and clutch are a rather large unit hung out on the end(about 1.09 sq ft surface blade area)..its subject to a lot of interesting dynamics..all of which can cause oscillation variations which will ultimately effect bearing life..because of the fan clutch the dynamic wt of the fan is variable hence balancing it with impellor is a rude event to say the least..the lighter plastic impellor is probably the best compromise but bearing failure still occurs..as the real mover is still the big arse fan/clutch combo..removing the combo minimizes the oscillation effects and should result in longer bearing life with any wp...Cheers! dk '97 2.8 bg R

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