950 Adv overheating with two fans?

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by Jdeks, Apr 21, 2013.

  1. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    Hey everyone,

    So I added a 2nd fan to my 04 Adv. Spliced it straight into the first fan's wiring, runs all fine and dandy, comes on with 5 bar on the temp gauge. But now it hits 5 bars way more frequently than it used to. It used to just come on in traffic or slogging around in 1st gear. But now,even cruising along dirt roads in 3rd at 60kph, 10 degrees outside, and the 5th bar lights up, fans buzzing away :huh

    It's not overheating per se - once it hits 5 bars and the fans come on, it cools down quick and switches off for a bit, then jumps back on, then off again, hovering around that upper 4th bar/lower 5th bar area. Never hits the 6th bar, even in hard work. When I put in the 2nd fan, I flushed and replaced the coolant. The radiator is full, and has stayed that way after a fair bit of riding so I assume its all burped out.

    I'm not sure if this is a bad thing. I think it's because having a second fan actually blocks off a section of the radiator that would normally have clean airflow through it, so until it starts running, it's actually impeding cooling. But I thought I'd ask if other people with 2 fans have seen this happen on their bikes, before I go buy the lower temp thermostat.

    Cheers !
    #1
  2. pdxmotorhead

    pdxmotorhead Long timer

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    Sounds like a flow problem, either air or pump, check for collapsed hoses..

    My bike 06 950, turns the fan on at 4 bars. Your temp sensor new old? they kinda fail randomly.. some last years, some dont..

    Cheers
    Dave
    #2
  3. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    Original switch. 04 bike, so it'd be nearly a decde old. But it obviously works - it's turning the fans on at the same place it always has - as soon as the 5th bar lights up.

    I though air in the lines too at first, but in the months since the change, it's been bumped, jostled, dropped and wheelied all over the place, so I would think that would have worked any air pockets out? The radiator is full to the cap too, and I can't see any pinched hoses.
    #3
  4. pdxmotorhead

    pdxmotorhead Long timer

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    Dang,, there ain't much more to it, unless your pump is not moving the coolant correctly.. Has the pump ever been out?

    Good Luck!
    Dave
    #4
  5. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    The pump has been replaced for preventative maintennance. CJdesigns hardened shaft and pump seal put in about 15000km ago, working fine prior to installing 2nd fan, no sign of it failing. When I drained the coolant I also took off the right engine cover for other work, inspected the pump and all went well. Fairly sure I put it back together correctly (nothing fits together if you dont set the impeller shaft properly).

    If the pump was fubar I think I'd be seeing far more severe overheating issues in any case.
    #5
  6. 99spike

    99spike n99b

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    My 2 fan kit came with a thermostat that switches 10deg cooler. Always runs 4 bar. I was led to believe that the thermostat was more important than the 2nd fan. The problem being that once too hot 1 fan cannot reduce temp, but if engaged soon enough 1 fan does fine. Also with 2nd fan insulated tanks. Did not test separately so can't confirm which change helped the most.
    #6
  7. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    Yea most kits seem to come with the low-temp switch.

    But I'm a cheap bastard, who scrounged a second fan and cable-tied it on :evil
    #7
  8. HeatXfer

    HeatXfer Bad knees

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    I have no experience with a dual fan set-up, but here are 2 things to check:
    1) Are both fans spinning in the right direction?
    2) You said you scrounged a fan: Any fan & shroud will restrict air flow through the radiator. If it's not designed for the application it could be restricting a lot of air flow until it comes on, causing the engine heat-up sooner and more often than normal. That's probably why you need a cooler set thermostat for a second fan.
    #8
  9. geometrician

    geometrician let's keep going...

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    Lower fan temp switch for sure

    radiator cap opening can look full when there is an air bubble in the LH high radiator hose. I suggest burping it if you don't have someone to help lift the front wheel when adding coolant.

    mud that becomes clay thrown into the radiator core from the front tire- I've doen some rides after a mud run and the bike ran hot until I soaked the dirt to get it soft enough to rinse out with a hose

    I've also had a)old gas (<6 months) from another bike and b)low octane/high ethanol content gas cause the bike to run hot- hot enough to worry me. Run some premium/super in it, and check out www.pure-gas.org
    #9
  10. Jaimoto

    Jaimoto Spaniard in Chile

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    Airflow on mine doesn't seem affected by the second fan (Head2wind fan kit)

    This is interesting:

    #10
  11. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    Thanks everyone. :)

    Yes, both fans sucking air through from the front.

    I'm thinking that 2) is probably the case

    Only 98 RON ethanol free gas ever used in this bike. Radiator looks clean.

    As for burping: like I said, this bike has been wheelied, laid over and generally ridden around for two months - surely this would have dislodged any air bubbles?

    In any case Whats the proper procedure for burping, so I can eliminate that for certain?

    Did you go for the lower thermostat with his kit?
    #11
  12. Jaimoto

    Jaimoto Spaniard in Chile

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    No, just the second fan. I would say my bike works in the same temp range as it did before the install, but now it cools down faster. No downsides on mine, I don't think I need the lower thermostat.
    #12
  13. HeatXfer

    HeatXfer Bad knees

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    I don't know if it's a DC brush motor that's polarity sensitive, but I figure it's worth a look.
    #13
  14. larryboy

    larryboy Chopper Rider

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    KISS

    Is the cap holding pressure? Does the cap gasket have cracks? Have you pressure tested the whole system? Is the thermostat stuck open?

    If it's sucking air or not holding pressure it will get hot and cycle the fans more often. Stuck open thermostat will flow water too fast and it won't get cooled by air flow.
    #14
  15. Head2Wind

    Head2Wind MotorcycleMayhem

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    Where did the "new" fan come from, assuming its a 4" fan? Is it intended for this application? How is the fan mounted?

    Generally speaking, the increase in obstruction of adding a additional fan is offset by the ability of it to move more air when energized.... But this is based upon the fan/system that I built. With both the second fan AND the lower temp switch the temp gauge hovers right around 4 bars.
    #15
  16. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    Doesn't piss out water when it's hot, no visible cracks on the cap gasket, so I assume it's holding pressure?

    How do I check if the thermostat is stuck open?

    It's a KTM 4" fan, got it new from Pyndon. Zip tied it on with rubber grommets to damp vibrations.

    Yep, that makes sense. Mine is only heating quickly when the fans are off - as soon as they kick in, it drops back down to 4 bars usually fairly quickly, unless I'm really slogging it. I'm thinking with the lower thermostat, it would never leave 4 bars at all...except Goti doesn't have that lower switch and he stays on 4 bars anyway?



    Here's the offending item:


    [​IMG]
    #16
  17. LateNate

    LateNate Been here awhile

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    What about oil? What kind of oil are you running? Maybe a heavier weight?

    I just installed my aux fan. Very recently so I haven't really had time to get the bike hot. Last summer one would come on in traffic and slow cruising around the trails here in MO where it gets pretty hot in the summer.

    Now thats its April, the two days I have ridden it, they have not been hot. The fans haven't kicked on at all! Not even in traffic. So I hope they are even working since I hooked them back up.

    I did however change the oil and have brand new oil in there. That maybe helps with cooling.

    I do not have the lower temp switch.
    #17
  18. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    The same old Motorex fully synth stuff that KTM recommends. Same as always.
    #18
  19. Jaimoto

    Jaimoto Spaniard in Chile

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    Well, actually I see 5 bars lots of times (traffic, slow off road,...) but I would say it was the same before the second fan install. The airflow should be worst than before but I can't tell the difference.

    Try removing the second fan see what happens?
    #19
  20. Muug

    Muug Muug

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    demito has the same problem: two fans and too hot, you can find him (here, perhaps, too) on lc8.nl.
    #20