Coolant problem

Discussion in 'Mechanics Garage' started by Jollyhart, Jun 8, 2018.

  1. Jollyhart

    Jollyhart New Member

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    Hi all.
    As stated I have a 5th gen coolant problem that is driving me nuts.
    The problem is that the coolant isn't returning to the radiators when it cools down.
    I have tried; 2 new (non honda caps)
    Replaced the clamps and hose running to the expansion tank.
    Pressurised the cooling system looking for leaks.Found a few loose clamps.
    Changed out the thermostat.It was stuck open.
    Compession tested the motor,all 160 psi apart from number 2 -150 psi.
    Leak down test -all good apart from a small drop on number 2 cylinder.Still well into the green though.
    There is no coolant in the oil or oil in the coolant.
    Bike runs really well.Temp sits at 76c when riding,fan switches on at 104c in traffic.Off at 95c.
    The bike doesn't appear to use coolant,but I do have to transfer coolant back from the expansion tank to the radiators after a few rides,approximately 50mls.
    Which means running without the fairings.
    I have also pulled the radiators off and flushed them out.They were pretty clean.
    I have drained and burped the system many times.I also use a large funnel to help the air escape during the process.
    I am thinking there has to be air getting into the system from somewhere, but if the system holds up to 18psi with no leaks for about 10 mins when cold, then perhaps it only happens when it is really hot?
    I am running out of diagnostic options,and ideas.
    The bike is a 2000 model with 102,000klms on it.
    Help!
     
  2. Diving Pete

    Diving Pete Member

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    You are losing it down the exhaust pipe.

    I think you may find your hydrocarbons in your emissions are threw the roof.

    It's a head gasket issue.
     
  3. Terry Smith

    Terry Smith Member

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    I had a pinhole leak on the radiator on my ST1100, and that dropped about 20mm in the filler neck each time I checked it. A pressure test when hot sounds like a sound idea to me.

    Are you sure you don't have a tiny air leak on the return hose or the fitting into the reservoir that it plugs onto?
     
  4. Jollyhart

    Jollyhart New Member

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    I forgot to mention that I had a mechanic test for hydrocarbons in the expansion tank and it was clear.And under the radiator cap it was clear as well for a time.
    Then it briefly showed a tiny amount of hydrocarbons (about 80) then went away.
    Apprently 1200 upwards is a blown head gasket.
    I have pressure tested the system when warm,but I think I will do another test with it hot and see what happens.
     
  5. OZ VFR

    OZ VFR Member

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    Have you checked that the return hose or the return tailpiece on your overflow tank is not clogged?
     
  6. Jollyhart

    Jollyhart New Member

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    Thanks Ozvfr and Terry Smith for the ideas.
    The hose from the radiator neck to the overflow bottle is new,as are the hose clamps.
    I have just checked the over flow hose from the expansion tank and it is clear.
    I also put a vacuum on the hose too and it holds pressure up to the cap.So I guess that checks out too.
     
  7. RllwJoe

    RllwJoe Insider

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    Correct me if I'm wrong. I'm understanding that the bike does not lose coolant. The coolant that is pushed into the expantion tank does not all return to the radiators, but stays in the expantion tank. Some how air enters the radiators to replace the displaced coolant.

    If this is the case, it doesn't sound like a bad head gasket. If it was a bad head gasket, it would push the coolant out of the expansion tank onto the road never to return. It sounds to me like air is being sucked into the system insted of the displaced coolant from the expansion tank when the motor cools down. You stated that you have new clamps and hose between the fill neck on the radiator and the tank. Could the nipple on the fill neck of the radiator have a crack where it attaches to the fill neck? If it did the overflow hose would have air in it when the motor cools down, thus pulling air not coolant into the system.

    Just a thought.
     
    Last edited: Sep 1, 2018
  8. Jollyhart

    Jollyhart New Member

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    Thanks for the ideas RllwJoe.
    I did just put a vacuum on the overflow hose going out of the expansion tank and it was holding fine.So I guess that the tank overflow line and the filler neck all hold vacuum.
    I am thinking I will just pull the motor and put some new gaskets in it.
    In the end it is a problem that I cant resolve easily.
    I did want to avoid the head gasket replacement but It looks like I have no options left.
    I will keep the forum updated when I have done the job.
    Thankyou one and all for your helpful suggestions.
     
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  9. Jollyhart

    Jollyhart New Member

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    I have some more news on the coolant problem.
    I have discovered that after a ride when the coolant is cooled it is slightly higher in the expansion tank than when I started.
    I then opened the radiator cap and sure enough there was an air space of about the same amount of coolant that is in the expansion tank.
    I then squeezed the air out of the system by pressing on the hose and then putting on the radiator cap.
    I have been riding around for a while without opening up the cap and it seems to be okay.
    I have yet to get the system really hot to really test it out,but for the moment I am happy to leave it alone and just ride.
    Fingers crossed,it may be okay.
    And the other good news is that I have a full top end gasket set for the future!
     
  10. OZ VFR

    OZ VFR Member

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    It sounds like there was still too much air in the system when you were closing it up.
    On a side note, when you check system with a vacuum, you should also check it with positive pressure.
    In refrigeration, some times a leak does not show up under vacuum as it pulls connections together, so you also need to check with high pressure.
     
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