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Thread: ST1300 - Solving the Coolant Leak Problem... For Good

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    Natural Rider Enhancement Blrfl's Avatar
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    ST1300 - Solving the Coolant Leak Problem... For Good

    I'm fed up with my ST dripping coolant when I start it up, so I've decided it's time to hit the war path and get rid of it.

    I think we've got two enemies one enemy here: vibration of the free-floating thermostat housing compounded by poor clamping.

    I explored ways to get the thermostat solidly bolted to the engine and didn't come up with anything useful. The closest thing to a real solution I could come up with was fabricating a bracket that bolts on with the hangar bracket on one end and connects to the housing between the housing's bolt heads and the housing itself at the other. I didn't find that a good place to start because the bracket would be difficult to fabricate, to reach around to the hanger bolts. Alternately, the bracket could be welded to a replacement hanger ($10), but I'm not sure what welding would do to its strength. I'd probably have to spec out longer bolts to hold the bracket and the thermostat housing together.

    That leaves the clamps, for which I think there's help.

    From what I've been able to learn so far, the worm gear clamps being used to secure the hoses are a large chunk of the problem. The perforations in the clamps allow what's called extrusion of the hose, the result of which is a loss of clamping torque. One manufacturer says that loss can be as much as 80%, which I suspect is a bit of an exaggeration given that the perforations don't make up 80% of the surface of the band. I think that, combined with the differing expansion rates of the aluminum and steel in the fittings and the shaking the whole free-floating thermostat housing gets are keeping the clamps from sealing and staying sealed. Two solutions look good:

    The one that looks the best from a mechanical standpoint are the Gates PowerGrip SB clamps. These are thermoplastic bands that attach to the hose and are shrunk to size over both sides of the bead in the fitting. Gates claims they contract as they get colder, maintaining a tight seal. They'd be impossible to replace on the road without carrying spares and require a $50 tool to remove. I'll pass.

    The next best thing is a constant-torque hose clamp, which adjusts itself with temperature to maintain a good seal. Breeze Industrial makes a model that looks like it will fit the bill. Gates makes something similar, but I wasn't able to find any information on them.

    The Breeze clamps come in sizes that can replace the #6 and #17 parts (see the attached drawing), but I'm not sure what size the #10 and #12 parts are. So if someone has that part of the system apart, I'd appreciate a measurement on the outside diameter of those hoses so can track down the right parts. Once I have everything I need, I'll do the replacement next time I strip the bike down and report on how it all did over the course of next winter.

    Updates and Other Info

    The clamps are Breeze P/N CT-9412 and are available from McMaster-Carr as P/N 54205K13.

    The torque for these clamps is 45 inch-pounds. Make sure they're torqued correctly or they won't work.

    Fall, 2009: I got the last of the clamps replaced this spring and had had no leakage so far. This has included a number of very cold mornings, when the bike is prone to it.
    Spring, 2010: Still no leaks, even after a long, cold winter in the garage.
    Fall, 2012: Still no leaks.
    Spring, 2014: Not a leak in sight.

    The five clamps that need to be replaced are highlighted in this photo:

    clamps.jpg

    [/FIELDSET]


    --Mark


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    Re: Solving the Coolant Leak Problem... For Good

    [Note: There was a post above this one that was posted by a troll who no longer exists.]

    Identifying the source of the leak isn't what I'm concerned with. I've been there, done that and got the tee shirt three times in the last three years. All three of mine have been the joints on the thermostat housing, and while I haven't verified it yet, I believe number four is, too.

    Eradicating the leak problem entirely is what I'm after here. My bike sees near-freezing temperatures in the winter and gets operated at 100 degrees ambient in the summer, and there's no reason the cooling system shouldn't be able to stay sealed over that range. I consider Honda's use of ordinary worm-gear clamps on a free-floating housing a design flaw, and I intend to fix it so i don't have to do out-of-cycle coolant changes when the joints leak.

    --Mark
    Last edited by Blrfl; 12-10-2008 at 05:57 PM.

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    Re: Solving the Coolant Leak Problem... For Good

    I don't know where the 80% clamping loss BS comes from...
    It comes from Breeze. Gates indirectly makes the claim but doesn't back it up with a number. I don't have a way to measure it, but between hose and neck shrinkage, I could see it. I'd have to dig for it, but I seem to remember someone here mentioning that their clamps had become loose enough to spin them around the hose by hand. That's a pretty good loss of clamping force.

    From your earlier post, it seemed like this had not been done on your 04 yet.
    It's been done three times in three years. In that post I was looking for a way to do it without draining the cooling system because I'd just changed the coolant (and gone over the hose clamps). All of my leaks have been at the thermostat housing, there hasn't been any need to pull the air box.

    The hoses set and then they leak. After a while they stop shrinking and there is no need for adjustment or extreme measures.
    I don't think clamp adjustment should be necessary at any time other than when the cooling system is apart for routine service. (Honda doesn't either, or they'd have put it on the to-do list.) I don't think replacing the clamps with better ones is extreme. Fabricating a bracket to hold the thermostat housing in place is a little extreme, but the only reason I thought about it was that I think Honda made a mistake when they did the free-floating design.

    --Mark

  4. #4

    Re: Solving the Coolant Leak Problem... For Good

    If those hose clamps are such a potential problem, how come my cars don't leak all the time?

    Hojo
    2006 ST1300 ABS
    IBA # 24485

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    Re: Solving the Coolant Leak Problem... For Good

    I would really like to have some confidence that the leaks can be stopped. I am on my third visit to the Honada dealer for leaks. I have chased them down myself and tightened every clamp there is to no avail.

    I am leary of getting an 07 because of the leaks the ST has experienced and so am looking at Ducati though not really sold on it yet either.

    Are the 06 models experiencing leaks?

    I have a friend with an 03 ST 1300 and he has never had a leak, not one problem with it and he has big temp. changes where he lives.
    STOC 324

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    Re: Solving the Coolant Leak Problem... For Good

    Quote Originally Posted by hojo in sc View Post
    If those hose clamps are such a potential problem, how come my cars don't leak all the time?
    If you look under the hood of your car you will see that a lot of constant tension spring-type clamps are used. These are those pesky ones that need their tabs or ends to be squeezed together in order to remove them, tricky without the right pliers sometimes. Since these clamps are free to close more tightly as the hose shrinks or sets within them, sized appropriately, they don't work loose as often. I wonder why Honda doesn't use more of these on their bikes. Our Toyota minivan has 140K on it and is loaded with these types of clamps. I've never had any kind of a coolant leak from this van.
    Last edited by wjbertrand; 04-27-2007 at 11:22 AM.

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    Re: Solving the Coolant Leak Problem... For Good

    Sorry guys, I posted this on another thread and meant to post it here........'

    I just want to comment with a little OEM automotive experience. Back in the 80's at American Motors (great company), we had Tridon worm drive clamps on rad hoses, which were torqued to their max. (30 in. lbs.) on line. The torque inspectors were driven nuts by the fact that 50% of that torque was lost a few minutes later. Then we started the new cars and drove them on a rolls test for 5 minutes, which heated up the cooling system. The torque would drop off some more after rolls. What happens is the first torque of hose clamps scrunches the hose toward the worm gear, then it heats up, and relaxes as it seeks to uniformly place itself around the thermostat or rad housing. Bottom line, retorque became a permanent reality after rolls.
    These days the OEMs are using constant tension spring band (with areas cut out to make narrow bands) or wire clamps. Wire are best because the wire can squeeze a hose better. Band clamps have too much surface area, and will always lose clamp load. I definitely believe constant tension types are best (Tridon, Breeze or Oetiker), but they aren't "mainstream" available to Joe Average without some searching. Our hoses are constantly cooling and heating up to 200F !!
    One additional thing all the OEM's do, they put a stop leak pellet in every rad. All coolant hoses weep a bit early in life, and this was meant to stop the weeping. We do this today even with all the high tech hoses and machined outlets, spring clamps, etc. Should we ST owners put a little stop leak into our systems? I suspect Mother Honda doesn't put that in bikes judging by the numbers with leaks.
    Anyway, something to think about. I am lucky, no leaks so far (that I've noticed).
    Ray

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    Re: Solving the Coolant Leak Problem... For Good

    Mark, I agree these coolant leaks are ridiculous and better engineering should be in place at the factory. The ST isn't the only bike with this problem nor is this a new problem. I commend you for trying to find a solution. Apparently some people are satisfied with the status quo or just don't know any better and are willing to tolerate having to pull plastic every 8k miles. I investigated the Gates thermoplastic clamps a while back and just never gave them a try. I believe they would be the answer. Fortunately I haven't had a habitual problem with leaks. A few months ago I smelled coolant. I didn't worry about it as I had put on 32k miles in the last year and was planning on changing the coolant and tightening the clamps anyway. It turned out not too much coolant was missing and although I was able to tighten all the clamps, I couldn't tell which one(s) was the culprit.

    Ray

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    Re: Solving the Coolant Leak Problem... For Good

    Thanks, Rays (both of you). Nice to know there's some interest in the topic. It was an effort not to continue feeding the trolls.

    Anyway...

    McMaster sells constant-torque clamps that look a lot like the Breeze clamps, and I think those are going to be what I try first since they're easy to get. (They're not in the habit of attaching brand names to most of what they sell, but I've been pleasantly surprised by what I get from them.) The clamps on the small hoses don't seem to be available in constant torque, but those aren't the ones that give me trouble. Later this summer, I plan to install an Audiovox cruise control, so I think I'll use that opportunity to do the swap.

    RayZ: Since you've got some experience in manufacturing these sort of things, I'm curious what you think about the free-floating thermostat housing design and whether or not the seal of the hoses would be compromised by its movement.

    I've also attached the missing drawing to the first message.

    --Mark


    P.S: My six-year-old wanted to type this: WIZZZZZZZZZZZZZZZZZZZZZZZZ

  10. #10
    Matt Kaminski UNTMatt's Avatar
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    Re: Solving the Coolant Leak Problem... For Good

    Thanks Mark, let us know how it goes. May pick up some of the same hose clamps if they work out for you and swap mine out at my next flush and fill.
    "Life is always a choice between greater and lesser risks -- zero risk is not an option." John Stossel
    "Complaining about the heat in Texas is like complaining about water for being wet." Reliant Energy

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