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ZX9 radiator has popped... Head gasket?

Discussion in 'Technical and Troubleshooting Torque' started by Loz, Nov 20, 2008.

  1. So a few months ago I was having coolant issues - after a long fast ride, if you stopped the engine, coolant would come firing out of the reservoir bottle and shoot a foot and a half in the air. Spectacular but embarrassing in public.

    I found I could control this by refilling the radiator while tilting the bike on extreme angles, which would release quite a decent amount of air bubbles. The bike would then run without shooting coolant for a certain amount of time, and then it would start again. Aha, I thought, there's a small air leak somewhere.

    So I plonked a thing of radiator stop-leak in the bike a couple months ago, and that stopped it altogether until last night, when I turned off the bike in the driveway. A few seconds later the radiator shat itself, and coolant and steam pissed straight out of the back of it somewhere. The bike hadn't been running at high temp, I'd just come down the freeway on a cool evening.

    I'm running through the possibilities in my head here, help me out:

    1 - stop leak solution decided to stop the leak that was the outlet to the reservoir bottle, and the resulting pressure blew the main radiator up

    2 - radiator cap thermostat gave out (an easy test to do anyway)

    3 - there's still an air leak somewhere

    4 - the head gasket has gone, and the bike is pumping exhaust gas into the coolant

    5 - I've suffered "wheelie damage" not dissimilar to what happened to Cheffie

    Right now I'm imagining a combination of 1 and 4, and not liking the implications. How hard is it to put on a new head gasket? :grin:

    Any ideas?

  2. On the right side top of radiator there is a small bolt, when the bike is hot loosen it slightly untill all air is released, then re-tension it.

    Sounds like you have an expanding pocket of air trapped in the radiator, same has happened to me before, worst part is bike shop will not necessarily tell you this, and charge for a major repair instead.

    See if this helps.
  3. Righto, can't do much with it right now 'coz it's got a hole in it and I'll have to get that repaired. But where's the air coming from?
  4. Loz, dunno mate... exhaust gases in radiator coolant tends to change the coolant's colour. Notice any change? There's a (pH?) test you can run if you have any left over coolant, that will confirm exhaust gas contamination. Did ya see any bubbles in the coolant? Whereabouts did the radiator shit itself?

    Won't be able to lend a hand during business hours, but have a few evenings available... Yell out if ya need a hand.
  5. Good point. A year and a half ago I had some coolant turn a bit brown, but since I replaced it, and have been topping it up from time to time with green stuff, the coolant has stayed bright green. So if it's not exhaust gases, where's the air coming from?

    Perhaps it's starting to look more like Cheffie's wheelie damage. That's encouraging.

    Anybody know a radiator repair shop near Pascoe Vale?
  6. Now I hope I haven't bollocksed anything by using that radiator stop leak stuff.
  7. From the hole? :LOL:

    Seriously, maybe you have had the coolant changed in the past and the system wasn't bled properly.

    I had the head gasket replaced on a bike I had and when it came back it was blowing coolant out of the resovoir every time it got hot, lazy mechanic hadn't bled the system properly. (or at all)
  8. Mmmm...

    It seems there's more air getting in there somehow though - each time I'd get all the air bubbles out (which sounds like it'd be a whole lot easier via that bolt than by lifting the bike down until it's a cm off the ground on both sides!) it would solve the problem - but only for a week or two.
  9. You could well be right, but you may want to try the no cost fix first.

    The small amount of air trapped at ambient temperature will expand considerably at 100 degrees.

    i was seeing the leakage out of the res and thinking damn head gaskit fix hasn't worked and then topping it up between rides only to have it happen the very next time.

    Funny thing was the amount of trapped was really minimal.
  10. Is it air or is it steam Loz?

    I assume water cooled bikes have a thermostat the same as cars, to regulate water flow and hence keep the engine near the prefered temperature. If a thermostat gets sticky it can remain closed above its set temperature, allowing the engine to over heat. When you stop the bike, there is no longer any air flow over the engine, and the water in the engine block can be further heated, finally boiling at high pressure, and blowing past the sticky thermostat. Sometimes just the pressure drop in the engine block due to the water pump stopping will result in the water immediately boiling, since the boiling point temperature drops as the pressure drops.

    If you are thinking, "but the engine didn't overheat", then remember that the temperature on the temperature gauge usually reads water temperature, and often it is the water temperature in the radiator, not in the engine. So if water isn't flowing, the temperature gauge reads wrong, usually low.

    Oh and yes, the radiator stop leak stuff probably didn't do much good. It could have made the thermostat worse. I don't think it would block the overflow though, or at least it shouldn't.

    Of course, you could have a leaking head gasket as well. Why don't you do a compression test on each cylinder and find out?
  11. can't you normally tell by letting the bike idle with the rad. cap off and see if it's blows bubles (rad must be full btw), i thought that was a sign the head gasket was was leaking? :?
  12. If you run the engine with the radiator cap off, until you can see the water flowing, (which is when the thermostat has opened to allow water to flow from the engine to the radiator) and top up the radiator to keep the water level visible, then yes, if you continue to get bubbles in the water it indicates a head gasket leak.

    Of course, it is a bit hard to do that test with a hole blown in the radiator.

    A compression test should show a noticable difference between cylinders, unless they are all leaking, or it is a very small leak, or your cylinders are all stuffed anyway.
  13. oh from one of his posts i thought he had it fixed, but yep that was what i was trying to say :wink:
  14. Interesting, I pulled the radiator off and while the vast majority of what came out was bright green, the last bits were rusty brown. Old corrosion and sediment or an indicator of possible head gasket issues?

    I'll take the radiator in for a fix now and think about causes later.
  15. Did the green stuff come out of the radiator, and the brown stuff out of the engine?

    If so, or likely, check the function of your thermostat. Pull it out, have a good look at it and confirm it is closed, then boil it in water on the stove and see if it opens up before 100°C. Check the temperature it opens at if you have a suitable thermometer and the patience to watch water boil.

    There should be specs in the manual saying the temperature at which it should open.

    EDIT: I would be getting the thermostat checked and/or replaced, and an engine flush done before I put a new (or reconditioned) radiator back on the bike. If the thermostat has failed, then the same rusty old water has been in your engine for ages, and has only moved now due to boiling the engine. A good clean of the water passages now will save you time, money, and another failure in the future.
  16. Pressure test of the radiator revealed no holes.... But a slightly dented water tube on the side Woodsy dropped it on. Thanks a bunch to the guys at Aussie radiators on Albion St, Essendon, who did the pressure test and fixed the bent tube for free.

    The bent tube might have been where the pressure finally got out.

    I've cleaned the thermostat and tested it (working fine) plus cleaned the thermostat housing. There's no blockages between the thermostat and the coolant reservoir.

    I'll flush the system out to get rid of any more brown stuff, then fill it up, bleed it and run it and see what happens.
  17. No, I opened the drain bolt at the water pump. Pure green came out until the very end, and then some brown gunky stuff came out. Then when I pulled the radiator off, and turned it upside down, a bit more brown dreggy stuff came out.
  18. There is nothing a good doughnut and coffee can't fix Loz.

    You can tell me all about it and I can nod at the appropriate times whilst partaking in the sweet goodness :grin:
  19. Yer on! Busy tonight?
  20. free as a bird