What else but another coolant leak

Hi All,

Happy Holidays! Some background info...my bike is a 2008 ABS model, bought it new in Jan 2009, currently has 42,000 miles on the odometer (shameful, I know, but that's what getting married and making babies does to your riding life ), and it's never leaked a drop of coolant. I started noticing a couple of drops of coolant on the garage floor under my bike about 6 weeks ago. The weird thing is that I'll take the bike out for a 1-2 hour ride say on a Saturday morning and then the following Wednesday or Thursday I'll notice the coolant on the floor. For lack of time, I've been ignoring it but I finally had some time last Saturday to peel off all the plastic and clean everything up. I took it out for a one hour ride (without all the plastic) and then parked it. I watched it every day this week (morning and night) and nothing showed up. It was perfectly clean all week. This morning (Saturday), I went out and checked it and sure enough there was some coolant on the floor. It must have leaked overnight. That's 7 days from the last time I rode it. See the pics. The best I can tell is that it seems to be coming from the area I'm pointing to in the 3rd picture (to the right of where the reserve hose comes out of the engine near the bolt and crevice). I don't see signs of leakage anywhere higher than that but I could be wrong. I plan to clean it up again, ride it, then park it, and see what happens.

Any opinions? I find it weird that it doesn't leak until several days after I've ridden it. Does the water pump have a weep hole like cars do to warn you that it's about to fail? Can I put some pressure on the coolant system through the radiator to better pinpoint where the leak is coming from?

Alright...my pictures got rotated 90 degrees CCW. How'd that happen???

Per Honda, some leaking is normal. I noticed when I had mine that a temperature drop would cause that, due to differing metals expanding/contracting... That does look like more than a few drops though and doesn't look like it's just from the weep hole/hose.

Classic ST1300 weep, seep, leak from a thermostat housing O ring or a hose or hoses that attach to it. The coolant runs downhill from between the Vee of the cylinder banks in a provided channel between the front cover and the engine block and exits out of the square hole on the lower right side. That is a drain channel coming down from above. Some coolant will run down the front of the engine if the leak gets worse. What we are talking about are minor leaks but they make a mess when mixed with road grime. Easy problem to deal with. It's not the water pump....if that leaks or weeps it comes out of the drain hose seen in pics #1 and #2.

Pull the plastics off again. Remove the radiator. Remove the frame cross member just above the engine that connects the frame across there. Two bolts secure the cross member, one on either side. Now you can see and work on the thermostat housing that resides there. Replacing the thermostat housing O ring is a given, Honda P/N 91361-MCS-A10. Snug the clamps on the hoses that attach to the thermostat housing and the two on the cylinder heads that connect the cylinder head join hoses. You will need a 6 mm socket and some extensions for a 1/4" rachet to get at the clamps. If you have a long flexible nut driver that will work too.

Some folks replace all the OEM clamps with constant pressure clamps and some just snug the clamps up. I dealt with weeps by simply snugging the clamps at 65,000 miles and of course the leaking O ring. I replaced all the hoses in the vee at 106,000 miles and sure enough at 165,000 miles I had another recurrence of this messy but minor problem. I did this just two weeks ago. I did replace one clamp this time.

PM me your email and I'll send you a step by step tutorial with pics detailing radiator removal and accessing the thermostat the easy way. The service manual tells us to remove the throttle bodies which is much more complicated.

This is common jafran, and is just not a big concern. Until you decide to repair it, make sure your overflow bottle is up to the Max fill line.

For a couple pics of mine (2004), see https://www.st-owners.com/forums/showthread.php?154355-And-Another-Coolant-Leak Your 2008 has the drain tube Honda added because dealers couldn't tell the drip leaks from water pump seal failures (so dealers were misdiagnosing many such drips as water pump seal issues). From where yours is leaking (by it not dripping from the drain tube), it is NOT the water pump. Yours shows classic drippy rubber hose connections under the throttle bodies that dduelin mentions.

I went in and snugged the various hose clamps under the throttle bodies a couple times by removing the radiator and working from the front of the engine. Mine still leaked every winter. So I've since replaced all the clamps with constant tension clamps, and that solved it (even in Colorado's VERY large temperature ranges). I've since also replaced all the hoses as they were due (after ~10 years) and reused the same constant tension clamps. Still no leaks.

You can see various pictures of the surgeries on mine here: https://www.st-owners.com/forums/showthread.php?38212-ST1300-1st-Significant-Service-Coolant-Thermostat-Starter-Valve-Synch-amp-Other

My bike did this for at least seven years, I finally fixed it about a year ago. Just do what dduelin and others under the "leaks" forum suggest. I have never spoken with another ST owner that did not ever have a cold weather coolant leak. They all do it; ST1100s are even worse.
One interesting thing I have noticed, with this weird cold/hot/cold weather we have had lately, during the hot and humid times, I had puddles of liquid under all four of my bikes due to condensation from the cold engine blocks. The ST is by far my oldest bike, so that condensation comes off a 14 year old dirty block, which can mimic an oil or coolant leak on first inspection.

Thanks guys. I've flushed the coolant system and replaced the thermostat before so I'm comfortable doing that myself. I have a spare thermostat and o-ring on hand too. I just don't have a lot of free time right now. I don't want to dump the coolant right now because the bike will be completely down for who knows how long. At least I can still ride it for now. I'm going to clean it up and try to pinpoint the leak again. When I have more time, I'll check all the hoses and connections and snug everything up.

Update:

My wife has family in town so she gave me the afternoon off yesterday while she hung out with her sister. (We have a new baby in the house.) My wife's brother-in-law is a do-it-yourself'er so we went we spent some time working on the bike. I put some pressure on the cooling system through the radiator and found several small leaks, including at the thermostat housing (or so it appeared). We went ahead and dumped the coolant, removed the radiator, swapped out the thermostat and o-ring and snugged everything up. Several of the hose clamps (mainly the smaller ones behind the radiator) were loose. I easily tightened them several turns each. I guess they loosen up over time. We added some new coolant and let the bike run for a few minutes. No visible leaks. It's cold out today so I haven't been out to check the bike. When the weather warms a bit, I'll take the bike out for a ride and keep checking it for a while before I put all the plastic back on. I'll be sure to top off the coolant too.

While I had an extra hand, I went ahead and flushed the clutch fluid too. That had been on my to-do list for a while.

The motorcycle specific MityVac 4510 ($35 on Amazon) came in quite handy. I learned something new. Evidently, most (all?) motorcycle radiator caps are universal. The MityVac 4510 came with two adapters, one to statically test the cooling system (shown in the pics below) and one to test the radiator cap. The adapter shown in the pics below easily fit my radiator. Also new to me....don't put more than 20 psi of pressure on your cooling system per the instructions.

Can someone tell me why my pics keep getting rotated 90 degrees?

Still rotating my pics

Time well spent.

jafran456 said:

I'll take the bike out for a ride and keep checking it for a while before I put all the plastic back on.

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This is going to sound completely backwards, but if you have hose clamp problems, the time you want to be looking for problems is when the engine is cold.

As the engine gets colder, the aluminum in the fittings, which has a higher coefficient of expansion than the steel in the clamps, shrinks enough to open up a small gap and make the clamp lose tension. When you first start up, coolant leaks through the gap until everything has warmed up enough that expansion seals it all up. For me it usually started with catching a whiff of hot coolant while underway and progressed into having a few tablespoons of it dribble out of the bike when being started cold on fall or winter mornings.

If you've tightened all of the clamps (including the ones in the vee, which are known leakers), you'll be fine until the engine has been heat cycled enough times for them to get loose again. I installed constant-tension clamps and haven't had so much as a drip since.

--Mark

And so it goes, we make our choices as best we see them. I've spent all of 5 minutes (maybe) tightening the OEM clamps several times over 10 years and 166,000 miles in response to a whiff of coolant and a few dribbles that made it out far enough to be seen.

How long does it take to replace all the clamps?

Agreed Mark, the seepage happens upon startup when the engine is the coldest. But the evidence is that it is moreso about the hardness of the rubber at low temperatures, coupled with the narrow band width moreso than the aspect of 'constant tension' of the hose clamps (because they are not constant tension).

From my worst-case calculations on thermal expansions of Stainless Steel vs Aluminum of the sizes of these parts in the ST, there's very little relative difference in shrinkage when the engine cools down. For a 1.25" Al nipple and a corresponding 1.50" SS hose clamp, through a 170*F temperature drop (from 190*F operating temperature to 20*F cold temperature), the Al nipple shrinks 0.00057" to 0.00016" more than the hose clamp (the differences based on the specific type of aluminum and stainless steel in the parts).

I just cannot believe that if the hose clamp diameter were adjusted by only 0.00057", these connections wouldn't leak. I do believe the 'constant tension' aspect can help a little bit, but it is moreso about the width of the 'constant tension' clamps (ie, about the area available for the rubber to seat itself upon), the specific fit of the rubber to the nipple under the hose clamp, and the suppleness of the rubber.

On my bike when it was leaking (yet again after tightening the hose clamps again again), it was very difficult to unseat the rubber hose from the aluminum--most of the circumference of the rubber hoses I pulled off of mine were in intimate, stationary contact (almost as if the hoses were 'bonded' by the coolant residue) to the aluminum nipple. Only a small portion of the circumference of the hoses under the clamps were free to move/flex to cause a seal, and that was a small portion directly under the narrow hose clamp, in one small arc of the circumference directly underneath the screw mechanism iteslf. Further, the hoses had taken a memory/set and were 'squished' enough that there wasn't enough flexibility left to seal around the nipple (even when tightened further), and the portion of the hose directly under the screw mechanism of the hose clamp wasn't tightened/squished equally with the rest of the circumference of the hose (somewhat visible on the left-most hose in this picture).


So in my experience, it is about the narrow band of the hose clamp, the uniformity of the clamping force around the circumference. If the clamp was originally too tight, and further tightened, the flex of the rubber to conform to the hose clamp and nipple makes it even more likely it will leak as the rubber gets cold. My replacing with new hoses and using the wider hose clamps with more uniform pressure applied around the full circumference solved the leakage (not 'constant tension' per se). The 'constant tension' hose clamps work because they're wider and because they remain more circular underneath the screw mechanism as they are tightened.

A fine point for sure, but worth the discussion.

I personally despise removing and replacing all the plastic, air box, throttle bodies, thermostat, radiator, whattever to get to anything so mine leaked for 5-6 years before I did anything about it. I may have lost about 8oz of coolant the whole time, maybe. Coolant and oil are kind of like blood, a little bit on the floor looks like a lot

BakerBoy said:

(because they are not constant tension).

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Are they constant- but not consistent-tension? Or do these clamps also stop applying tension over time? I have no experience with such clamps other that the spring type with tabs that are squeezed with a pair of pliers to install remove or adjust. In looking at ad copy various vendors claim that these maintain tension/torque under expansion/contraction where the typical screw drives (eventually?) would not.

BakerBoy said:

Only a small portion of the circumference of the hoses under the clamps were free to move/flex to cause a seal [or leak?], and that was a small portion directly under the narrow hose clamp, in one small arc of the circumference directly underneath the screw mechanism iteslf. Further, the hoses had taken a memory/set and were 'squished' enough that there wasn't enough flexibility left to seal around the nipple (even when tightened further), and the portion of the hose directly under the screw mechanism of the hose clamp wasn't tightened/squished equally with the rest of the circumference of the hose

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If I'm understanding this correctly: if you chose to accept the remove the plastic and retighten regimen a slight rotation of the clamp relocating the space under the screw to a 'bonded' part of the circumference should eliminate further leaking.

This supposes that you could still get to the screw to tighten it after rotating the clamp and that the now-bonded area under the new positioning of the clamp didn't eventually loosen and leak.

At the first sign of a coolant leak I think I'd be happier 'upgrading' the clamps to minimize periodic maintenance.

ST Gui said:

Are they constant- but not consistent-tension? Or do these clamps also stop applying tension over time? I have no experience with such clamps other that the spring type with tabs that are squeezed with a pair of pliers to install remove or adjust. In looking at ad copy various vendors claim that these maintain tension/torque under expansion/contraction where the typical screw drives (eventually?) would not.
...

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The manufacturer claims 'constant torque' (which is not constant tension). http://www.breezehoseclamps.com/breeze/constant-torque/ On this forum, many have referred to them as 'constant tension' (and I left that vernacular unchanged in my reply above). The bolt through the clamp is at constant torque, but even so, that does not provide constant tension through the band as it expands and contracts with temperature.

But for perspective, the breeze clamp circumference changes less with temperature than typical hose clamps because the series of Belleville washers takes up a portion of the contraction and expansion. The constant torque mechanism is actually a stack of washers acting as spring (and springs take more force [torque] to compress further). While the bolt through the clamp isn't changing position--is at 'constant torque'--that doesn't translate to constant tension. In the fine details, the bolt isn't at constant torque either, but that's splitting hairs.

As the stack of Belleville washers are compressed (ie, as the hose clamp band cools and shortens), the tension actually increases slightly in the band. But, that slight increase in tension in the band is less than occurs for a solid band of a typical hose clamp, so these constant torque clamps are better than typical band hose clamps.

ST Gui said:

...
If I'm understanding this correctly: if you chose to accept the remove the plastic and retighten regimen a slight rotation of the clamp relocating the space under the screw to a 'bonded' part of the circumference should eliminate further leaking.

This supposes that you could still get to the screw to tighten it after rotating the clamp and that the now-bonded area under the new positioning of the clamp didn't eventually loosen and leak.

At the first sign of a coolant leak I think I'd be happier 'upgrading' the clamps to minimize periodic maintenance.

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One of the features that the manufacturer recognizes and states as part of the improvement of the Breeze clamp is: "This unique design eliminates ?cold flow? leaks. ... clamps have an extended inner liner which protects all types of hoses from damage and helps to maintain consistent sealing pressure." The bold emphasis is mine, and emphasizes a key benefit of the Breeze clamps: the inner liner (the inner portion of the band circumference) overlaps the outer band quite a ways around the circumference to keeps the hose from bunching up in one portion of the circumference, especially underneath the clamp mechanism of typical clamps.

Another very obvious change in the Breeze clamps is the width of the band... they're almost 2x as wide as the Honda OEM clamps. So, it applies pressure over a larger area, more consistently, than OEM clamps.

I agree with your thoughts ... anytime the Honda factory clamps are tightened, it is best if they are first loosened and rotated so that the screw mechanism is positioned elsewhere around the circumference. In doing that, the 'bunched up' part of the hose that was under the screw mechanism will get a chance to seal because it will now have hose clamp band appliying pressure on that area. I'm not sure it will guarantee a seal, but it would likely have a better chance at sealing.

I too tried the 'tighten the hose clamps" approach a couple times, but mine only got worse. The best solution was the improvement brought by the Breeze clamps, primarily the uniform pressure it applies around the full circumference, across a wider area.

dduelin said:

And so it goes, we make our choices as best we see them. I've spent all of 5 minutes (maybe) tightening the OEM clamps several times over 10 years and 166,000 miles in response to a whiff of coolant and a few dribbles that made it out far enough to be seen.

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I have no explanation for why my bike leaked consistently in cold weather and yours didn't. I don't plan to find one, because the cost isn't worth it when there's an inexpensive fix that I can make and move on. For all either of us knows, Honda changed suppliers and between model years got better ones that still met their specs or my hoses were put on at 4:45 on a Friday afternoon.

If yours doesn't leak, great. Mine started the first time the weather turned cold after I bought it. I had the ground cap recall done the following spring, so I got them to tighten the clamps under warranty (actually, I just told them it leaked when cold). The same happened the following two seasons, and after that, I started replacing the clamps. I didn't get around to the very last one until 2009, and eight years on I have yet to see so much as a drip.

How long does it take to replace all the clamps?

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Once you're under there, a few minutes per clamp, and it isn't like I wasn't taking the Tupperware off for maintenance or farkling anyway.

--Mark

Yes, I don't know why either. I suspect it has something to do with differences in winter temperatures coupled with bikes laid up for weeks or months on end vs. bikes ridden often year round in temps over 35 F. Also snugging a clamp vs. wailing on it and crushing the hose is a nuance perhaps overlooked.

Like we have posted here and in the past there are a couple of approaches here that seem to have worked for at least some of us.

dduelin said:

.... Also snugging a clamp vs. wailing on it and crushing the hose is a nuance perhaps overlooked.
....

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If you're inferring that is what I did, you're barking up the wrong tree.