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Thread: still overheating! Don't know what to do anymore!

  1. #1
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    Exclamation still overheating! Don't know what to do anymore!

    for about 1.5 years now i have had an overheating problem with my 1997 528i (130k), it always starts to overheat when i am going at slow speeds or idling but i only let it reach about 3/4 mark.

    Replaced thermostat/Water pump----5000 miles ago
    Replaced cracked radiator-----3000 miles ago
    coolant flush------1000 miles ago

    My car still continues to over heat at low speeds or when it is idling. i don't know what could be the problem anymore. could the water pump (plastic impeller) or thermostat gone bad already?

    also ever since it started overheating, on the passenger sides no warm air comes out anymore. when i put it to hot, the drivers side blows hot air, while the passenger side does not. any ideas what could be wrong? Thanks
    Last edited by skate1bmw; 12-19-2009 at 10:21 PM.

  2. #2
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    Replace the entire cooling system, all hoses and everything else.

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  3. #3
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    Sounds to me that the system has not been properly bled.
    2007 Carerra S
    2009 E91
    1990 Toyo PU - POS
    2000 E39/5
    1976 911

  4. #4
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    how would any of you bleed the system? maybe that could be a problem that i didn't right?

  5. #5
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    I would try bleeding it. The replacement waterpump you installed has a plastic impeller?

    some bleeding discussions:

    http://www.bimmerboard.com/forums/posts/199986

    http://forums.bimmerforums.com/forum...d.php?t=953107
    Last edited by Doc325i; 12-19-2009 at 06:23 PM.

  6. #6
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    skate1bmw,

    Please consider updating your carlist to reflect the model and model year or production date of your car.

    I agree with the need to properly bleed the cooling system, however, I don't think there is any need for a complete cooling system overhaul. Start with a proper bleed and work from there (I'm not recommending throwing parts at the problem!).
    528i M52 cooling system bleeding, overhaul, overheating
    You may have to read through a bit of that thread to find the posts on bleeding the system. You can also run a search in that thread for "bleeding" to save time.
    Finally, I would also consider replacing the fan and fan clutch since those important components have not yet been done. A failing fan clutch can destroy your hood and many other crucial parts in close proximity.





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    Last edited by jamesdc4; 12-20-2009 at 02:30 AM.

  7. #7
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    the replacement water pump has a plastic impeller on it, could that be the problem??

  8. #8
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    Nope are you loosing coolant ever? If so I would check the hoses for a crack that could be expanding and letting coolant out when it gets hot. But most likely it needs to be properly bled. If you have air in the system it will cause all the problems you mentioned bleeding is easy. Unscrew bleeder screw on top of the coolant fill up tank then let car idle for like ten minutes and it will blow air bubbles out of that small hole. Once only liquid it coming out it is properly bled and should solve all of your issues.

  9. #9
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    coolant levels are fine. i have bled it until no bubbles are coming out. i heard that some people raise theire cars about 6 inches or so but i havn't done it like that yet.

  10. #10
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    and it still overheats?? Did you just add coolant when you filled it up last time? Because it has to be 50/50 mix with water or it will not work to transfer heat

  11. #11
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    Quote Originally Posted by honda954racer03 View Post
    bleeding is easy. Unscrew bleeder screw on top of the coolant fill up tank then let car idle for like ten minutes and it will blow air bubbles out of that small hole. Once only liquid it coming out it is properly bled and should solve all of your issues.
    Your post and help is very much appreciated, however, you only post a partial bleed of the cooling system.
    _________________________________________
    http://www.bmwtips.com/tipsntricks/JC/Overheating.htm
    Over Heating Check List
    by Jim Cash on 2002-11-04
    I would suggest checking the coolant, and making sure it is bled properly - which can be a rather involved process to do it correctly.
    The basics
    Cold engine
    - check that coolant level is correct
    - Ignition on but engine not running
    - set heater temp settings to max
    - set fan manual to one of the lower speeds
    - start engine and within 30 seconds rev it 3-4 times up to 3000rpm
    - shut off engine before end of 30 seconds (before it starts to heat)
    - reset climate to normal settings
    - recheck coolant and top up if necessary.
    Hot engine
    - take car for a run to get up to operating temp
    - using caution - slowly open the bleed valve (steam and bubbles may come out)
    - close as soon as you see liquid coolant without excessive bubbles.
    - do not overtighten this as they are plastic threads. Just snug till it seals fully.
    - after engine cools check the coolant level again and top up if necessary.
    Check coolant level every few days for a few weeks and top up again if required
    - repeat the Hot engine bleed process again.
    If coolant keeps droping after 2-3 top ups have the system pressure tested.
    If you are still getting over temps have it analysed by a dealer. The temp is controlled by the engine computer so there may be another fault.
    Cheers
    Jim Cash
    _____________________________________
    Parking on an incline or raising the front of the car, as mentioned in an earlier post, is also helpful when trying to bleed the cooling system.
    Once again, I highly recommend reading through the cooling system thread I posted in post #6 above. There are lessons to be learned from other member's experience.
    Last edited by jamesdc4; 12-20-2009 at 01:33 PM.

  12. #12
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    If the engine is only overheating at low road speeds or while stationary, you have an airflow or coolant flow issue. Check that the fan clutch and auxiliary fans are working properly, and that the radiator is not obstructed. If these check out, the problem is coolant flow at low speeds. This could be caused by a slipping belt (perhaps caused by a bad tensioner), a water pump impeller slipping on its shaft, or a partially collapsed hose. You will need to do a methodical check of these components. Begin with those external to the engine, then move to the water pump.





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  13. #13
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    all start doing that tomorrow. the water pump was replaced with a plastic impeller and i have read that the aftermarket metal impellers are better. when i am on the freeway it doesn't over heat. when it does overheat though, i just give it gas and the temperature goes back to normal. i will check everything all u guys have told me so far and i will let you know what happens. the last thing i want to do is take it to the stealership. thanks for all your help so far though.

  14. #14
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    I am thinking more now than ever you have a bad fan clutch. When you spin the fan by hand do you get much resistance?
    2007 Carerra S
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    2000 E39/5
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  15. #15
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    the resistance is fine, i checked it by hand it there was resistance, i even compared it with my e36 m3 and they feel the same. i also checked it when it was spinning with a newspaper, and the clutch fan is working properly.

  16. #16
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    Quote Originally Posted by 02Pilot View Post
    If the engine is only overheating at low road speeds or while stationary, you have an airflow or coolant flow issue. Check that the fan clutch and auxiliary fans are working properly, and that the radiator is not obstructed. If these check out, the problem is coolant flow at low speeds. This could be caused by a slipping belt (perhaps caused by a bad tensioner), a water pump impeller slipping on its shaft, or a partially collapsed hose. You will need to do a methodical check of these components. Begin with those external to the engine, then move to the water pump.
    Definitely follow this checklist. Exactly what I was thinking and covers anything that it most likely is at this point. Good luck op post up with you figure it out. Aux fan is a good one too, I forgot about that.

  17. #17
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    hmm i thought of another possible problem/solution. The previous water pump was broken inside into a lot of pieces, and a mechanic replaced it. when it started to overheat again, i notice some sort of hard plastic piece in the coolant reservoir that was blocking the hose at the bottom. since only the drivers side blows heat, i am assuming that one of the old water pump pieces is now blocking a heater hose, and possibly blocking another hose somewhere else.

    if there was a piece of the old water pump in the system how would i go about removing it?

  18. #18
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    i agree with the fact pieces are causing u to loose heat but if the blockage was causing ur car to overheat it would do it no matter what, not just at idle. also the auxillary fan should come on with the ac on. feeling for resistance in the clutch isnt sufficient diagnosis cus the problem with those are the fact they dont lock up when they reach a certain temp. if it was locked when u stuck ur news paper in it it woulda knocked it clean out ur hand
    Never drive faster than ur gaurdian angel can fly

  19. #19
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    Replace the fan clutch--and the fan while your at it---this is the very reason that
    we all replace the entire cooling system when it's time--failure to do so results in just what your going through--throwing money at parts --with out knowing which one is bad--

  20. #20
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    Question: Assume that your plastic water pump self destructed into pieces. What is the procedure to remove the small parts?

    Question: Is the OEM original water pump on an 03 530 contain plastic impellers? (please do not guess, reply if you know for a fact) It seems that the plastic impeller water pumps were on/off at times on original installations at the factory from reading different posts.

  21. #21
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    A blockage in the system may be the cause of the cabin heat problem, but it is not the issue causing the general overheating. You have to think of the radiator as a heat exchanger. A certain amount of coolant must flow through to dissipate enough heat to offset the heat generated by combustion. Operating at maximum efficiency, the radiator has surplus cooling capacity and this is not a problem. By reducing either the airflow or the coolant flow, the ability of the radiator to shed sufficient heat is impaired, resulting in overheating. Bear in mind that the engine generates more heat when driving than it does at idle. This means that the radiator must shed more heat when at speed than when at idle; this is compensated for by the increased airflow created by motion of the car (the fans are only capable of generating airflow equivalent to traveling about 15mph maximum) and the increased flow of coolant created by spinning the water pump faster. Therefore, a debris blockage in the system would reduce the flow of coolant in all conditions and create an exacerbated overheating condition when at speed.

    Low speed/idle overheating is usually an airflow issue, but it can be caused by insufficient coolant flow, however only under conditions that allow flow to increase at speed; these are insufficient flow from the water pump or a constriction in a hose that is overcome by increased pumping pressure at speed (the latter is quite unlikely, especially if your cooling system is holding pressure correctly, but I have seen it).





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  22. #22
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    [QUOTE=gtxragtop;18210658]Question: Assume that your plastic water pump self destructed into pieces. What is the procedure to remove the small parts?

    When the plastic impeller went on my E34, I used a wet/dry vac to get out as many of the plastic pieces as I could.
    Oxford Green 1998 540i/6
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  23. #23
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    Fan Clutch. when you're idle, the clutch doesn't engage completely because it's faulty and hence overheating. I had this same prob.

  24. #24
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    I had this exact problem off and on for several months. I always noticed it at seasonal changes whenever I started to use the heat. I bled and re-bled the system, but could never seem to get coolant to "flow" from the bleeder screw.

    I double checked for leaks and discovered a small tiny pinhole leak directly beneath the thermostat housing. So small, in fact, that the leaking coolant would immediately evaporate. I replaced the thermostat housing, jacked the front of the car up and added coolant at the thermostat bleed screw with the key on, engine off, heat set to highest, fan set to lowest. When I did this, I could hear the secondary water pump (for the heater core) turning and spitting bubbles. Each time I added coolant the level in the overflow tank would rise then drop slowly. I must have put close to a quart of additional coolant in before it stopped.

    Once that was done, I started the car and let it warm up, front end still in the air. Then when I cracked the bleed screw at the thermostat housing I got a few bubbles and a steady flow of coolant. No problems since then, but I'm still wary when I get stuck in traffic.

    As far as your half heat in the interior, I would suspect some kind of blockage or vent circuit not working. Good luck with that. Hope the above helps you out.
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  25. #25
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    Quote Originally Posted by BaltimoreBimmer View Post
    Sounds to me that the system has not been properly bled.
    +10000000000 for it!!!!!!!!!1

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