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Looking for Opinions.. ZZR250 - Overheating

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Dire Nutz, Dec 16, 2013.

  1. Ok, soo... This is the Situation, I think I have narrowed it down to a couple of Possibilities.

    Basically - A head gasket or a Cracked head.

    So I top the Radiator up to full ( the Bottle has correct Level ) The bike runs Beautifully, Go out for a "Decent" ride around Semi city/Rural for 45min - 1hr by the time the hour is up the bike is Running Close to hot, Get home let it cool down and it's used about 300ML of Water. Enough to heat the engine up.

    So, ive looked for Leaks there are none, nothing coming out of the exhaust etc.

    Considered a few things,
    - Blocked hose between radiator and bottle
    - Thermostat stuck open or Closed
    - Cracked head
    - Blown Head gasket ( unlikely but possible )

    before I start Stripping the bike to find a solution thought i'd get some more Opinions.
    • Like Like x 1
  2. Start with the cheapest parts first.
    blow through the overflow hose.
    Radiator cap? Just cos
    Perished hose? These can look ok, but can leak under pressure. And if its steam coming out you won't see it.
    Also squeeze them, if they are kind of stiff and feel 'crunchy' they are ready to fail.
    Really hard to tell while riding, go round the block to warm it up then let it idle for a few minutes till the fan comes on, grab a beer, and watch carefully, with fairings off makes it easier (ps do this outside so you don't asphyxiate)
    Thermostat? Rule out the other 2first.but it should come up to normal in 1or2mins not more.
  3. Only Replaced radiator cap last month, I was going to check all the Hoses and Could be a perished hose, as I said Wanted some more Opinions before I got stuck into it.

    My next stop was the Thermostat. Glad I'm thinking along the right lines...

    Cant sell it if it's Overheating :(
  4. Haha that's the next option, just sell it.
  5. Has your engine oil gone milky or like creamed honey?
    Mayonaise like goop under oil filler cap?
  6. Nope, Clean as. Only done 2000Km's since Rebuilding the Top end. oil is Almost as good as when it went in.

    What would you say if it was? just in case I'm Mistaken

    And yeah, I was going to sell it in a few months and upgrade. might just sell it to save time and money.
  7. Water is getting in the sump if the oil goes milky/creamy/thick and the mayonaise stuff appears, it usually indicates a blown head gasket. Since you aren't getting that it points away from a blown head gasket. Can still be leaking from water jacket to exterior though, but you'd probably see a bit of coolant under the bike after it's been parked and smell it when it was hot.
  8. Is the fan coming on?
  9. could be leaky water pump?
  10. Yeah, I thought of that too, but you'd reckon you'd see a puddle under the bike when it was parked. Also thought the water pump impeller may have failed and water flow could be inadequate.
  11. well for it to use 300ml over the course of an hour it's probably coming out as a tiny spray or mist, could be evaporating on the hot engine before even developing a puddle once parked (whilst still hot) plus not leaking at all whilst under no pressure.
  12. You could take the thermostat out and test it, just put it in a saucepan of water and bring it to the boil, it should open before the water boils.
  13. IMHO its less likely to be a leaky hose as you'd probably see some evidence, but if something (dead impeller, partially blocked hose) is compromising the cooling it could be losing coolant as steam from the overflow as it overheats, so nothing to see when you get home.
    Try a temporary extension to the overflow hose to where you can see it while riding.
  14. It can still be a blown head gasket if there's no coolant in the oil, it's just unusual. I had an old Tarago do that. Coolant was leaking straight into the cylinders. The break in the gasket also formed a "flap" that kept combustion gasses in but sucked in coolant, so the usual gas test strip the mechanics use didn't pick it up. Pain in the arse it was.

    Just to confirm, Dire Nuts, you are using coolant and not just straight water? Plain water will boil faster and could be steaming out. If it's only done this once or twice since the rebuild, are you sure you bled the system out properly in the first place? Air trapped in the cooling jacket can make it seem like it's using coolant, but it will stop once it's finally "burped" out.
    • Like Like x 1
  15. Crap guys thanks for all the Replys, Yeah we "Burped" the system afterwards, The head gasket was New, So im Ruling that out till I go through everything else,
    I am using Coolant not Water, Luckily Im not That Stupid haha

    Im going to Check the Hoses For Blockages, if all Clear ill Check the ThermoStat.

    The Fan is Coming on, Ive got the Fan Hard Wired ( on with the Key ) atm to Help Keep it Cool.

    If that's all cool, ill give the Pump a Look.

    Starting on it Tomorrow, Will Hopefully Have some Good Luck
  16. Ok its been awhile, but thanks for all the help, I stripped it down, the radiator and all hoses/cooling system was clear. took the Thermostat out, it was stuck open. tested it a few times with the stove, it would open but not close. I got a new one, put it in and the bike Seemed to be doing ALOT better, been good for a week or so, coolant started to get a tad low, so I topped it up.

    then my Problems started to appear.

    1. It's still Overheating
    2. An Excess Amount of coolant is coming out of the overflow pipe from the bottle. spraying down onto my rear brake and tyre. Obviously a big problem.

    now I am assuming it's overheating from a lack of coolant, Judging From the Amount it's leaking and the Amount im Putting back in.

    I'm going to get the Head Gasket checked by my mate soon ( Mechanic... He has the thing they put on the radiator to check for gasses etc )

    if it's not that, ill check the water pump.

    Now, sorry for the long post. BUT does anyone have any other Theories? Especially as to why it's Dumping a lot of coolant
  17. Coolant may spilling out of the overflow because your bike is overheating, or your bike might be overheating because coolant is spilling out of the overflow. Once you've refilled the cooling system fully, the temperature at which coolant begins spilling out of the overflow will be a helpful hint about what is happening.

    If coolant is boiling in the overflow and spilling out long before the system overheats, then either:
    1) Your radiator cap is not holding enough pressure and needs to be replaced (again).
    2) Your head gasket is gone - exhaust gases are entering the cooling system, upping the pressure and pushing coolant out of the overflow.

    If coolant is boiling and spilling out once (i.e. because) the system is overheating, then there is some other problem. The coolant probably isn't circulating - there is a blockage somewhere or your water pump isn't working.
  18. With the motor running have radiator cap off and keep filling it up and see if bubbles keep coming up. If so water is leaking into cylinder past head gasket. Pull both plugs out and if one of them is nice and clean then u have deffinite water in cylinder