Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Coolant Overflow

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by nudge, Sep 11, 2008.

  1. Hey guys,
    Recently flushed my coolant. Ever since I am getting quite a lot of coolant overflow (pipe in front of rear tyre) and it does not seem to be drawing water from the overflow tank.

    So in summary - Coolant goes out the overflow drain hose, radiator level drops, but overflow tank stays full.

    I suspect I may have air in the system somewhere, but I do not know the way to get rid of it, or if it is even the problem.
  2. It could be a leaky head gasket or warped cylinder head that's allowing escaping combustion gasses to pressurise the cooling system and blow the coolant overboard via your overflow tank.
    If you're lucky you might be able to hear some bloop bloop sounds in the overflow tank when the engine is idling.
    If you can hear any blooping or gurgling sounds whilst the engine is running 'tis almost certain to be a rooted head gasket or other cylinder head problem.
  3. No sounds or anything in the overflow tank. taking the lid off and having a look into it while the bike is running and there is just a slight swirling on the surface of it.

    I'll have a better look into it over this coming weekend
  4. It could be combustion leakage but may be as simple as an air-lock/ cavitation problem. Given that you've just drained the system and presuming you've had no previous problem...

    -Take the radiator cap off.

    -Fill coolant to bottom of cap flange.

    -Tilt the bike left and right until you can almost touch the clip-on on the floor. Lean it right over. You can do this a number of times and keep topping up the coolant as needed.

    Run bike (upright) until hot before refitting cap.

    DON"T overfill the surge tank.
  5. I think that did the trick. leaning it right over one way caused a string of bubbles to come up to the radiator cap (didn't do it as spirited as the clip on to the floor, probably at a 40-45 degree angle to the floor). topped it up, put the cap on and did some more spirited leans. checked level and it was fine. ran with cap off and the level rose (? that seemed odd, I was expecting the level to drop)

    Put cap back on and did my normal ride to and from work and it seems fine. No more overflow.

    Thanks MSCRacing. I hope this is the end to my problem.
  6. It is normal for the volume of the antifreeze/coolant to increase as the engine warms and decrease as it cools. That is why there is an overflow tank and a 2 way valve in the radiator cap that allows hot coolant to expand and flow into the coolant reservoir then flow back into the radiator when the engine cools and a partial vacuum forms in the radiator. The coolant reservoir has an upper and lower level usually marked hot and cold. Ethylene glycol has a higher boiling point and a lower freezing point than water. It was introduced widely when alloy motors became common place in cars and bikes. Tap water often can be acidic or alkaline plus have a lot of minerals. These react with alloy to form white gunk and crusty deposits that can erode gaskets and block radiators. Prior to alloy engines, car radiators were filled with water in warm countries like Australia and didn't have overflow tanks. Cast iron motors always developed sludgy rust deposits and radiators had to be flushed routinely. It's a mistake too use tap water in any bike cooling system unless there is no choice. I think most bikes use concentrated ethylene glycol and their should be no need for mixing. Cooling systems are pretty reliable these days and coolant replacement is only needed once in a few years if low mileage and once a year if 25,000 km+. Mfg may say shorter intervals but I have never had trouble with longer intervals. 2 nasty properties of coolant are it's slippery if it spills on the road or gets on the tyre and it is sweet and poisionous, so don't let your dog (or child) drink it. In low concentrations it is used to clean windows. I can't remember if it strips paint but that might be brake fluid I'm thinking of.
  7. I'm assuming coolant is the coldie at the end of the ride.

    Bit worried about the coolant overflow though. Have you talked to a doctor?