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Thread: Water pump failure or temp gauge sender failure?

  1. #1
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    Water pump failure or temp gauge sender failure?

    Again, thanks for the previous help.
    My temp gauge goes all the way to the red line.
    So I just installed a new radiator and 180* thermostat.
    Gauge still goes to the red line.
    I checked the thermostat in boiling water. It's fine.
    The new thermostat is fully open at 190*.

    Reinstalled Tstat and bled all the air.
    Still goes to the red line.
    Temp probe reads as high as 206*at the top of the radiator
    BUT I DON'T SEE fluid flowing across the cap opening.
    Upper radiator hose is hot.
    Lower radiator hose it NOT hot.
    The upper and side Tstat hoses are HOT.
    Auxiliary fan is NOT coming on.
    (Yes, I have confirmed that the Auxiliary fan actually works.)

    Here is what I think is wrong.
    I think my water pump is not working (but it's not making noise either).
    That makes sense because:
    I don't see coolant flowing across the cap opening.
    The thermostat probably opens but that won't help because fluid isn't flowing into the top of the tank.
    The auxiliary fan switch never comes on because the coolant in the lower half of the tank isn't getting hot.

    What do the experts think?
    2001 Boil Tstat.jpg2001 radiator outlet.jpg2001 switch.jpg2001 lower hose.jpg2001 bushing.JPG
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  2. #2
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    If your lower hose is cold typically that is a bad thermostat however since you tested it I would bet money the water pump is bad.

  3. #3
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    more pics
    2001 new tab.jpg2001 lower clip.jpg2001 shroud clip.jpg2001 Old Tstat.jpg100_1481.jpg

    - - - Updated - - -

    Quote Originally Posted by charter21p5 View Post
    If your lower hose is cold typically that is a bad thermostat however since you tested it I would bet money the water pump is bad.
    I agree but I have never had a bad water pump that wasn't making some sort of bad noise or fan wobble.
    Visit my 1977 320i Build and BLOG page HERE.

  4. #4
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    Can't you ground out the temp gauge to see if it is working:?
    jm

  5. #5
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    Quote Originally Posted by 2002jm View Post
    Can't you ground out the temp gauge to see if it is working:?
    jm
    Temp gauge is working properly. It starts out on the left and gradually moves to the right.
    Visit my 1977 320i Build and BLOG page HERE.

  6. #6
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    Probably have a rusted water pump impeller that's where I'd start

    Sent from my HTC 10 using Tapatalk

  7. #7
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    Did you set the heater control valve on 'full hot' when you refilled/bled the cooling system?

    This may be irrelevant to the issue, just thought I'd ask...
    Last edited by epmedia; 10-20-2016 at 06:14 AM.
    Tbd

  8. #8
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    My dash heater controls are jacked up. I don't think they work at all. I think the water pump impeller is the problem.

  9. #9
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    Water temp sender switch is good? I guess you could check resistance on that or they're $7. You can jumper the aux fan just like the fuel pump to see if the relay works but, I think it's 87 to 30 (instead of 15 on the FP) don't quote me on that but, when looking at the relay, it's the top one and the one to the (ccw) left of it.

    I would have to guess water pump too because, down here my car has never got hot enough to need the fan.

    - - - Updated - - -

    Unless you had a leak or blew the head or something. You can strip it down to the water pump and turn it over (someone else) real quick to see.


  10. #10
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    I see coolant flowing across the top of the radiator on all the other vehicles I own. But not on this BMW radiator. I've ordered a new water pump. Just another adventure.

  11. #11
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    I've never been able to look in my e21 radiator and confirm water pump in this car but yeah, sounds like the right thing to do.


  12. #12
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    Lugnutz: You can actuate the heater control valve from the engine bay. (or at least you can on the 80's models).
    "The most important thing is balance." - KT

  13. #13
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    Quote Originally Posted by FranzE21 View Post
    Lugnutz: You can actuate the heater control valve from the engine bay. (or at least you can on the 80's models).
    The '77 heater valve is under the dash. It's easy to manipulate if it's not stuck. If it's stuck, I wouldn't mess with it just yet.
    Last edited by epmedia; 10-20-2016 at 11:24 PM.
    Tbd

  14. #14
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    Something went well today. I actually fixed the overheating problem. I just don't know for sure HOW I fixed it. LOL!
    I had decided that the old water pump had failed. WRONG! It was fine and looked pretty nice actually. The only thing I can figure is that I had a major air bubble trapped somewhere inside the engine and it was preventing the old water pump from moving any coolant.

    Anyhow, it's fixed. Gauge never goes above half now. The day was frustrated by sheared off alternator bolts that wouldn't budge. The pictures show some of the differences between the water pumps. Different impellers. Rock Auto probably has me on their Christmas card list of people who buy parts but don't really need them.

    Thanks again for all the help.
    IMG_0446.jpgIMG_0449.jpgIMG_0450.jpgIMG_0453.jpgIMG_0456.jpg
    Visit my 1977 320i Build and BLOG page HERE.

  15. #15
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    ^ Is it fixed, or not?
    Your other thread says otherwise...

    fyi: it's best to keep the same topic in the same thread to avoid confusion
    Tbd

  16. #16
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    I clearly say that I fixed the overheating problem. What other thread are you referring to? I started this thread with the topic of "a possible failed water pump". I stayed on topic since this is my follow up message.
    Last edited by Lugnutz77; 10-24-2016 at 07:01 AM.

  17. #17
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    Quote Originally Posted by Lugnutz77 View Post
    I clearly say that I fixed the overheating problem. What other thread are you referring to? I started this thread with the topic of "a possible failed water pump". I stayed on topic since this is my follow up message.
    Oh crap, sorry! I got mixed up between yours and Lugnuts threads. Carry on...

    And good job.
    Tbd

  18. #18
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    Ummmm, . . . . this is Lugnutz77.
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  19. #19
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    Quote Originally Posted by Lugnutz77 View Post
    Ummmm, . . . . this is Lugnutz77.
    Lol, I meant to say Laptop's thread
    Tbd

  20. #20
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    Quote Originally Posted by Lugnutz77 View Post
    Something went well today. I actually fixed the overheating problem. I just don't know for sure HOW I fixed it. LOL!
    I had decided that the old water pump had failed. WRONG! It was fine and looked pretty nice actually. The only thing I can figure is that I had a major air bubble trapped somewhere inside the engine and it was preventing the old water pump from moving any coolant.

    Anyhow, it's fixed. Gauge never goes above half now. The day was frustrated by sheared off alternator bolts that wouldn't budge. The pictures show some of the differences between the water pumps. Different impellers. Rock Auto probably has me on their Christmas card list of people who buy parts but don't really need them.

    Thanks again for all the help.
    IMG_0446.jpgIMG_0449.jpgIMG_0450.jpgIMG_0453.jpgIMG_0456.jpg
    Lugnutz...or whoever you are pretending to be...lol

    Thanks for posting how you tracked your overheating issue.

    I'm still laughing about "epmedia" calling you out...

    Anyway, any issues with the car since your last post on the water pump?
    Last edited by SilverPuddle; 06-11-2018 at 08:57 PM.

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