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ZRX1200 -- still chasing overheating problem, update on post #5

Discussion in 'The Garage' started by 2wheelsrbest, Aug 8, 2019.

  1. 2wheelsrbest

    2wheelsrbest Been here awhile

    Joined:
    Jun 23, 2007
    Oddometer:
    440
    Location:
    North Central WA
    2005 ZRX, has water temp gauge rather than stock idiot light

    Normally gauge reads 225-ish and fan kicks on. I recently noticed that temp gauge was going past that toward 250 and fan still not kicking on. It was overdue on coolant maintenance, so I dove in. I knew the coolant was clean/green, it was just a few years since I changed, so I did that first and bled the water pump.

    Fan fuse--good, swapped with spare fuse for good measure, fan runs when I jump wires

    Thermo switch--tested repeatedly in boiling water with VOM and it connects right around when it should.

    Thermostat--tested in boiling water and it also opens when it should

    Old coolant was clean, so I am not thinking there is any blockage, but I am now wondering about water pump. System is filled, though top neck where thermostat lives is open. I taped up a catch bottle and cranked engine with starter for 15-20 seconds. No coolant. Tried again and engine fired on the fumes of what was left in carbs, so it ran on it's own a little bit. No coolant came hosing out. Checked bleed of water pump again, cranked with starter and still nothing squirting out...

    This points at water pump, correct?

    I have a lot of other things on my plate/mind these days and simply want to check my troubleshooting logic. Thanks for any input.
    #1
  2. RetiredandRiding

    RetiredandRiding Retired to Ride Supporter

    Joined:
    May 22, 2015
    Oddometer:
    1,614
    Location:
    Left Coast, United States of Covid
    When you drained the coolant, was there enough to fill the system? Did you run a garden hose to it and flush it? When you added coolant, did you add enough to, per the owner's or service manual, to fill the system? If not, it could be a blockage.

    If I understand correctly, you're basically running the engine with the radiator cap off, right? When I do that with my DRZ, the coolant doesn't overflow, it just bubbles past the opening. It takes a few seconds after the engine starts for this to happen, but not 15. Unsure what else it would be other than the water pump.

    Good luck!

    /
    #2
  3. patmo

    patmo Long timer

    Joined:
    Dec 2, 2010
    Oddometer:
    1,350
    Location:
    Northern Kentucky
    Many years ago I had the same problem on my 2000 ZRX. To make a long story short, it turned out that the fins on my water pump had all dissolved over time (70K/10 year’s), even though I had changed the coolant on a timely basis. Perhaps a faulty batch of parts? It wasn’t hard, or expensive to change.
    #3
  4. 2wheelsrbest

    2wheelsrbest Been here awhile

    Joined:
    Jun 23, 2007
    Oddometer:
    440
    Location:
    North Central WA
    Ample coolant before draining--yes, full to cap and top bleed nipple on this bike
    Flush it--yes, old coolant wasn't dirty at all, just old, but I flushed it for good measure
    Put enough back in--yes, again filled to filler cap and expanded out of bleed nipple with engine warming up

    This system has a junction above head that houses temp sensor, thermostat, highest point in system and bleed nipple all in one spot. It's handy.

    My water pump test has this junction open and no thermostat, with output dumping into a bottle, rather than into radiator. I figured when engine turned over, whether running or just on starter, coolant should come gushing out, which it does not.

    I guess I could pressurize the To Radiator side of the system with air compressor and verify coolant flows through system. That would show/prove no blockage and point to water pump ($250, boo).
    #4
  5. 2wheelsrbest

    2wheelsrbest Been here awhile

    Joined:
    Jun 23, 2007
    Oddometer:
    440
    Location:
    North Central WA
    October, 2019

    Still chasing this problem.

    Further testing of water pump and inspection make me think this is not the issue. I removed water pump and it looks brand new inside. Impeller good, no corrosion, etc.. I reinstalled, refilled and retested for flow, which it DOES have. I must have not had quite enough in system to see flow.

    I am now questioning whether my water temperature gauge is working correctly. I have tested sender and it seemed to be off from what VDO specs I could find. VDO has yet to reply to my email/call to get accurate specs, so I ordered a new sensor. Installed, it still reads 250F+ before the radiator fan comes on.

    As the radiator fan works and thermo switch tests at correct temp, I'd like to measure the coolant temp some other way. Is outside hose temperature a good indicator of internal coolant temp? I was thinking of some way to dip electronic oven/cooking thermometer into the coolant via the bleeder valve above thermostat, but that may be overthinking it. If coolant temperature was 225-250F, the outside of the hose should be close to that temp, correct?

    Each time I test, I am letting bike warm up to where GAUGE reads 225F, which has historically been the point that radiator fan would kick on. I wait and wait as temp creeps higher and then turn bike off at 250, because I don't want to damage anything.

    Open to ideas and suggestions.
    #5
  6. Motomantra

    Motomantra Registered Lurker

    Joined:
    Mar 6, 2008
    Oddometer:
    3,155
    Location:
    Beaverton, OR
    If you want a temp gauge, go to Harbor Freight, get an infrared temp gun. https://www.harborfreight.com/search?q=laser infrared thermometer
    The hoses will not be close to actual coolant temp.
    What happens if you warm it up with your hand on the top of the radiator, where the hose goes in? You should be able to verify by feel the T-stat opening as the temp gauge reaches operating temp. It should get hot quick.
    I dunno, that's all I got. These bikes are bullet proof. How many miles?
    #6
    dtysdalx2 likes this.
  7. Zoef zoef

    Zoef zoef Long timer

    Joined:
    Apr 19, 2009
    Oddometer:
    1,288
    Location:
    Finnøy Island, near Stavanger, Norway
    Could be air in the system at the themoswitch for the fan. Means that the thermoswitch does not feel watertemperature.
    #7
  8. 2wheelsrbest

    2wheelsrbest Been here awhile

    Joined:
    Jun 23, 2007
    Oddometer:
    440
    Location:
    North Central WA
    Motomantra--ZRX is a 2005 with 18k. I was also thinking of pulling the thermostat and testing the rest of the system that way. Tstat DID seem to open well in the boiling water on stove test, but perhaps it is a bit off or getting stuck. If that were the case, that would explain the hot gauge sensor, but not-hot-enough fan switch.
    #8
  9. 2wheelsrbest

    2wheelsrbest Been here awhile

    Joined:
    Jun 23, 2007
    Oddometer:
    440
    Location:
    North Central WA
    Zoef Zoef--True, but each time I've pulled the thermoswitch, there was coolant ready to leak out and plenty of it. Thermoswitch sits fairly high in radiator, so I know it is immersed.

    Appreciate the ideas, guys.
    #9
  10. 2wheelsrbest

    2wheelsrbest Been here awhile

    Joined:
    Jun 23, 2007
    Oddometer:
    440
    Location:
    North Central WA
    FFS...

    Just got done testing it without any thermostat in it. Guess I just wanted to make sure it was not at issue, even though I tested it on the stove. Gauge went to 225, then toward 250 where I shut it down with no fan action.

    During this test, I had been checking the temps with IR thermo I have. Radiator was getting hot, for sure. I measured 204F at the thermoswitch at one point. After I shut bike down, I pulled thermoswitch connector apart. Jump wires to fan = fan goes on. Test circuit to switch and it is still open. So, EVEN THOUGH THIS IS THE FIRST THING I TESTED, it appears that the thermoswitch is at least part of the problem. Once this MFr cools down, I may check continuity of the wires to the switch to the plug. Very frustrating.

    I love the look of this bike, but it has been more hassle than all the other motorcycles I've ever owned. It has some super sweet design elements (rear axle adjuster) and some things that are very well thought out (valve adjustment fingers that hold shims in place), but it has not been very reliable (coils, carbs and now coolant).
    #10
  11. MotoChris521

    MotoChris521 motominded

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    Aug 30, 2007
    Oddometer:
    3,268
    Location:
    south west
    Try bypassing the fan switch , if it runs at normal temp, then you can focus on the fan circuit.
    #11
  12. 2wheelsrbest

    2wheelsrbest Been here awhile

    Joined:
    Jun 23, 2007
    Oddometer:
    440
    Location:
    North Central WA
    MotoChris521--Thank you! I was talking with a friend on Saturday about this and he had suggested the same. Makes perfect sense and is something I should have done much earlier in this project. I have a manual fan switch on my DRZ, so I know what it is all about. It just seems like where my life is at and the time/attention I have available for this, my past trouble-shooting skills are a bit off. I appreciate this site's members to help get me back on track.

    As I had last tested the system without the thermostat installed, I took a minute this morning to boil test the t-stat. Again. It opens at the proper 180F as marked.

    Now just need some time...
    #12
  13. zeerx

    zeerx Long timer

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    Feb 21, 2007
    Oddometer:
    1,438
    Location:
    Haverhill, MA
    Did you bleed the water pump? There’s a bleed screw at the high point of the pump housing.
    #13