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Thread: coolant leak!

  1. #11
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    Re: coolant leak!

    maybe ll wait for pump!? its got a 90k mile life if I remember correctly? last year I did faulty thermostat, and I already bought carb boots to replace when I go back in threre!

  2. #12
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    Re: coolant leak!

    Actually, only the timing belt replacement interval is 90K miles- the pump/seal should really last a lot longer than that, assuming the coolant was changed with a non silicate type from time to time. I used the premixed Prestone Prediluted AFZ- AF2100 and that one is silicate free (and ~ $8 per gallon vs the blue bottle Honda brand that’s no doubt more money). If you have a leak, I hope it’s something minor.
    Bob 2000 ST1100/1994 ST1100 ABS (now in Dark Gray!)

  3. #13
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    Re: coolant leak!

    Quote Originally Posted by MattK View Post
    maybe ll wait for pump!? its got a 90k mile life if I remember correctly? last year I did faulty thermostat, and I already bought carb boots to replace when I go back in threre!
    You'd best determine where the leak is first. If you know you have used the wrong coolant and if it is the pump leaking, not fixing it runs the risk of the coolant contaminating the timing belt, which could then slip while running and destroy valves.

  4. #14
    STOC #687 dwalby's Avatar
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    Re: coolant leak!

    Quote Originally Posted by Bush View Post
    You'd best determine where the leak is first. If you know you have used the wrong coolant and if it is the pump leaking, not fixing it runs the risk of the coolant contaminating the timing belt, which could then slip while running and destroy valves.
    The timing belt teeth mesh tightly on two cam gears plus the crank gear, so there's not much chance of it changing its timing just because a little coolant drips on it.

    But I don't know how long I'd want to ride around on a leaky water pump. I don't know if a leaky seal could eventually cause the impeller bearing to seize, but if that were to happen then you're going to potentially damage the timing belt through friction (it drives the water pump impeller) and that would be very bad for the engine.

  5. #15
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    Re: coolant leak!

    Quote Originally Posted by dwalby View Post
    The timing belt teeth mesh tightly on two cam gears plus the crank gear, so there's not much chance of it changing its timing just because a little coolant drips on it.
    Disagree. Coolant is very slippery.

  6. #16
    STOC #687 dwalby's Avatar
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    Re: coolant leak!

    Quote Originally Posted by Bush View Post
    Disagree. Coolant is very slippery.
    But the tension on the belt keeps the teeth in tight contact with the sprockets, so I don't see how its going to jump a tooth just because its slippery. I'd think the belt would have to lose some tension before that could possibly happen, and they seem to be pretty tight when you take them off for replacement. But, the small crankshaft sprocket is the most likely location for it to slip, and that's right below the water pump, so I wouldn't say its impossible, but I'm not sure its very likely either. Do you know of a case where that actually happened?

  7. #17
    Bush's Avatar
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    Re: coolant leak!

    I can't identify a specific case, but it is something I learned in the auto trade decades ago and there are references to oil or coolant leakage problems with belts on a number of Googled pages. Here's a cut and paste from one:

    "Fluid Leaking From Timing Cover
    Oil and coolant leaks from the timing belt cover tell us that the belt may be saturated with contaminants. A saturated timing belt is much more likely to break or slip. These conditions may result in catastrophic engine failure. Leaking water pumps, crankshaft seals, camshaft seals, and oil pump seals are likely causes of fluid leaking from the timing cover."

    So, without looking under the timing cover to see the extent of leakage, one can't really tell if the belt has just had a few drips, or is much more contaminated. Then there is the possibility of bearing seizure on the pump, as Doug mentioned. All in all, the OP would be wise to FIND the leak and if it is the water pump, not delay in a repair.
    Last edited by Bush; 02-13-2018 at 06:39 PM.

  8. #18
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    Re: coolant leak!

    Quote Originally Posted by MattK View Post
    maybe ll wait for pump!? its got a 90k mile life if I remember correctly? last year I did faulty thermostat, and I already bought carb boots to replace when I go back in threre!
    All other input seems 'all-good', but my bet is the two coolant elbows, one on each head. Replace them and their sealing O-rings. Those elbows ARE notorious for frackering from many heating cooling cycles over the years. So, with that, I'd definitely make use of those new carb boots at same time. You'll find the original carb boots are stiff and hard. I had to replace coolant elbows and carb boots at 80,000mi. One elbow was fractured and carb boots were no longer flexible.
    1992 ST1100
    1981 Yamaha XS Venturer 1100

  9. #19
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    Re: coolant leak!

    thanks for the suggestions, its gonna be 40 today in Chicago so im sure after work ill warm that bike up and then inspect!! ill keep you ppl posted!!

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  11. #20
    Site Supporter Jim Van's Avatar
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    Re: coolant leak!

    Quote Originally Posted by Bush View Post
    That could indicate a leaking water pump seal.
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