How do I know if cooling system is fully bled?

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by keener, Jun 10, 2013.

  1. keener

    keener Speed changes you.

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    Replaced the water pump shaft,... as preventative maintenance after 40000km...I have tried to bleed the system by pumping the left rad hose several times and raising the front wheel too. I when for a ride and the coolant level in the reserve came down about half an inch at most.

    Bike is not over heating or anything. How do I know if it is fully bled? What are the symptoms of having air in the cooling system?
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  2. Balsta

    Balsta Been here awhile

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    Just let it cool down after the ride, open the radiator cap, and do a final fill.
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  3. MortimerSickle

    MortimerSickle Semi-Adventurer

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    I too have wondered about this, but only a little, because in the almost six years I have had my 950, I have never done the front wheel lift routine.

    The cooling system has always worked fine.

    The only time I ever had an overheating problem was when the dealer's mechanic left the fan unplugged- one reason I now do all my own work.
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  4. crazybrit

    crazybrit Long timer

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    I always bleed at the water pump. Then (with the bike running) remove the small bolt from the top of the left radiator until coolant flows out of it.

    After it cools I'll remove the cap and check the level in the radiator and overflow tank.

    I've never done the front wheel raising trick either but the repair manual does say that it needs to be raised.


    EDIT
    the note in the shop manual says " NOTE: to completely bleed the cooling system, the motorcycle must beraised approx. 50 cm in the front - see Technical Information"

    All the other references to "see technical information" in the manual refer specifically to it being in "chapter 1" but I don't see anything useful in that chapter. What am I missing?
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  5. keener

    keener Speed changes you.

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    Thx guys...I have no trouble bleeding the system. I think there is no air in there as far I as I can tell by coolant flowing out of all bleed holes.

    The question is, how do I know if it is fully bled? What are the symptoms of having air in the system?
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  6. crazybrit

    crazybrit Long timer

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    overheating
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  7. ICERIDER

    ICERIDER Adventure Rider

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    :rofl Nice answer!

    When I did my 5.5 I didn't raise the front either. I just kept bleeding/top-up/running/bleeding etc until I didn't need to top-up any more. Actually last time I just used the rad cap with the bike parked on the side stand as the final bleed point as it seemed to be higher than the bleed screw on the LHS of the rad.

    Is the theory for the front to be raised so that the front head is higher than the aft? Can't remember how it's plumbed in the heads as my bike is 8000 miles away :cry

    I'm hoping that in practice the velocity of the coolant flushing through will evacuate any air after a few cycles of topping up. The manufacturer can't depend on that though and has to advise a more positive bleeding routine I guess. Could it be that?
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  8. MortimerSickle

    MortimerSickle Semi-Adventurer

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    I once saw a post saying that air gets trapped in the waterjacket of the rear cylinder when the bike is filled on the level.

    Maybe that is true?
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  9. Deepc

    Deepc Been here awhile

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    Just my 02 cents. I bleed at water pump, then at the radiator, then I pull the rear wheel and bleed at radiator with my front wheel in the air. I've also heard that pumping the rubber coolant hoses with your fingers might help. I haven't had any overheating issues since using this method.
    #9
  10. keener

    keener Speed changes you.

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    I have used the pumping the 1" hose on the left side method several times and it works just fine. I pump it a few times then open the top left rad bleed bolt and squeeze the hose once again until coolant starts coming out, and put the bold back on tight and let go of the hose.

    I don't have overheating issue, so I guess all the air is out.
    #10
  11. Yascher

    Yascher Been here awhile

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    it needs to be raised, as the heads cooling cavities are not paralle to the ground and will trap air!
    In order not to overheat heads, it is required to lift te front, so the coolant can completely displace air from heads....but the best thing is to start it on the sidestand and gas it on/off to let the air out and top up as needed. Close the cap and fill the expansion bottle to the high mark. When the bike cools down, it will suck the required amount of coolant from expansion bottle back into the system and level should stay on the MIN when COLD and HIGH when HOT.

    Just to be sure all is good, just do a small wheelie or a hill climb when hot and it should get all the iar out to the rad
    #11
  12. Katoom72

    Katoom72 Been here awhile

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    I just fill it up like the manual says (but without lifting the front) and wheelie the heck out of it. 0 cooling problems on any of my lc8's
    #12
  13. HellsAlien

    HellsAlien a has-been that never-was

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    To answer the OP: you will know the system is fully bled of air when the coolant level on the overflow tank returns to the same level after the bike cools back to room temp.

    Put a mark on the tank 1/2 way between the high and low marks, work to that. Check it the next morning after a ride.

    In my experience, raising the front wheel does help bleed air out of the motor. I proved this to myself one day by filling the radiator on the level, then running front wheel up some stairs, blocked the sidestand a bit, but kept the radiator cap at high point of the cooling system. When I pulled the cap on the stairs, there was a big burp of air. It took another significant slug of coolant. Put the cap back on, went riding. Level came right back to the mark on the tank when cooled down.
    #13