Coolant leak around water pump cover?

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Let me throw a couple little things out here that have not been discussed.
While some people just want to try to snug or tighten the loose clamps in an attempt to fix leaks, this is NOT a good idea by itself, the reason being is once the clamps loosen up over time and heat cycles, the coolant then seeps past the clamp and gets on the metal pipe (side of T-stat body housing) and starts to corrode and rust the metal fittings, causing even more leaks! Its a much better idea to remove the T-stat housing completely and clean or wire brush the fittings before putting it back on or tightening it up more.
Another area that is commonly missed is the water pump housing o-ring that is mentioned here. When it fails it leaks coolant past the o-ring and onto the LEDGE that joins the two surfaces together on the front of the engine, this coolant then slides down the ledge and leaks out of the SQUARE hole, making people think that its the clamps up in the VEE area.
To be safe (and not have to do it a second or third time) when you are working with leaks in this area you should replace the water pump housing o-ring, remove and clean the T-stat housing, replace the T-stat and o-ring, and verify that it is not a failing water pump (weep hole) and while your in there, clean all the black paint off the radiator elbows (inside and out).
This will normally fix your coolant leak issues, short of a damaged hose.
If anyone would like to see pictures of what the fittings look like during a leak repair process, PM me a phone number or email address and I'll send some your way.
Igofar
 
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Can you help me to determine whether the leak is coming from the round hole or square hole. Attached are pics.

Igofar and SuperSabra and few others, I have followed your posting for many years now. i just want to thank you for all your inputs. With them I was able to solve a lot of the ST1300 problems on my own. Thanks.

The bike is a 2007 ST1300, 81,000 miles, was in the vee area to tighten the hose clamps 4 months ago. The stain on the side of the motor is from then about 4,000 miles.
Kenny
 

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Damn, you got a pretty serious leak going on there! Did you clean the area around the ROUND weep hole inspecting it? If not, it looks like the water pump mechanical seal went south and its pumping out enough coolant to keep that small area clean (I hope I'm wrong).
I would not ride the bike any further until you figure out whats going on!
Pull the radiator, remove the cross brace, pull your T-stat housing out, (Good time to replace the T-stat and O-ring), with 81,000 miles on it, I would go ahead and replace all the hoses for peace of mind, and so you don't have to do it again later.
Pull the hoses off the T-stat housing and check the metal pipes the hoses attach to. I'm betting you have rust and or corrosion on them causing them to leak also.
With that much coolant leaking, My guess would be: 1. waterpump went south. 2. Hose rubbed against a hoseclamp and caused puncture. 3. Corrosion on T-stat pipes. 4. Front water pump cover gasket died along time ago, causing the coolant to leak out near the alignment dowels and run down the sloped edge of the cover and out the square hole making it look worse than it really is (I hope I'm right on this one).
5. Every clamp in the vee is either loose, or over tightened, causing leaks.
Let us know what you find.

Funny thing is, I also have a 2007 with 81,000 miles on it :rofl1:
 
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Igofar, thank you for your quick response. I am wondering which hole, round or square, is leaking more. I am going to run the ST while it is on its centre stand to observe the leak. According to what I read from this forum, if it leaks heavily from the round hole, the meachnical seal on the water pump is done. If it is leaking mainly from the square hole, then it is the hose clamps etc in the engine vee, as well the O-ring on the water pump cover. Am I correct in this assumption?
I am comfortable in replaceing the thermostat and replacing the clamps. I did that at 20,000 miles. But nervous about changing out the water pump. I don't know a place with a hydraulic press. There are hora stories about the sproket and chain dropping down during the removal of the front crankcase cover.
Anyone knows what this "ruler trick" on the removal of the front cover is about?
Kenny
 

Blrfl

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Before you start removing radiators and water pumps and doing all kinds of surgery...

If the round hole wasn't cleaned before you took the picture, that's not the source of your leak and the the water pump seal is fine. It's not coming from upstairs, either because there's no way it would have come out of the square hole and covered the area above it unless they have some kind of weird gravity up there in Canada. :)

Based on what appears to be the spray pattern, I think the large water hose is leaking at the fitting.

--Mark
 
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If you see a drop out the round hole every couple seconds (like a heart beat) your mechanical seal is probably to blame.
If you didn't clean the small "clean" area around the round hole before you took the picture, that could mean you have enough coolant coming out to "clean off" the area (think of trickle of water into dirty pan) the impact area where the coolant is flowing, may be cleaning that small area around the hole? As far as "weird gravity" up in Canada....its called wind and turbulence, anything leaking out of the square hole is blown back, up, and all around, and the edge of the small hole often catches it. Try running a clean cotton pipe cleaner into the round hole to clean it, then run the bike, then do it again to see if the coolant is coming out the round hole, or being caught by the blow back. But I do like the Weird gravity comment :rolleyes:
 
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I say it's from the round hole because the hot coolant comes out the round hole while hot and cleans that area, then the coolant cools down and creates the mess.. Thanks what I think
 
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Well, thanks for all your input. The mess is very recent. I cleaned that whole area 3,000 miles ago. The gravity is the same as US in Canada, but we can go faster on the highway because of less police around to give out tickets. The stain is harden caked on antifreeze. I guess the hot engine evaporated the leak soon after it came out. I didn't clean the round hole, it is the way it is. It does feel wet still. Everywhere else is caked on.
Tonight or tomorrow morning, I'll run the bike on it centre stand to see where the leak is coming from. Hope it is something I can repair myself.
Igofar, since we have the same bike with the same miles, can I say Wegofar?
Kenny
 
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Kenny, it would be my honor to ride with you.
Let us know what happens. The water pump is do-able with hand tools, a couple sockets, a couple pieces of PVC, and a small Arbor press (think harbor freight).
The hardest thing to do is scrape the dang gasket off the engine/cover.
 
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This is a mystery. I just ran the bike on its centre stand for 1/2 hour. The fan cycled on countless times. Each time the fan came on, I could smell coolant. But there is no leak at all coming out of either round or square hole. There are no leaks from anywhere that I could see. I checked for leaks as the engine cooled, still no leak at all. So I am concluding that the culprit are the hoses and clamps up on the vee. Am I correct?
But the mystery is how did the caked on coolant mess around the round and sqaure holes get there. I can't explain it. Only thing out of ordinary happened in the past weeks was that I dropped the ST on it's left side at a stop sign. Picked it up within 5 minutes. Could that cause the sudden rush of coolant leak?
Kenny
Igofar, I may take you up on that ride one day. Bucket list includes ride to California from BC Canada.
 
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Check the three way tee fitting on the hose that comes off the radiator cap area. Find it at the cap and follow it backwards, it rests between the radiator and the front of the right cylinder head. Honda uses work clamps to attach the lines, and the plastic tee cracks. This is your coolant return line so if the fitting leaks it does so a lot.
It could be the hoses heating up as pressure builds and if there is a crack there you won't see it until the tee is wiggled or you move it by hand while running. Be careful it will pump hot coolant out when they break!
Another thought, could your radiator have taken a stone hit and it's spraying coolant rearward?
 
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I am going to order an O-ring for the water pump cover today. Then I'll drop the radiator to find the leak. I already have some new clamps and hoses. But before I open up the water pump cover, does anyone know what the torque ft/lb is for these bolts?
Thank you, Kenny
 

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I have the same problem but only at cold start and temps in the 50's or below. Stops once bike has warmed up.
Watch it carefully, mine went from doing that to leaking all of the time within 2 months. My culprit was the upper right hose clamp on the thermostat housing, if you are looking at it from the front if the bike.

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Any suggestions for me? I too have discovered a leak and I'm trying to figure out how bad it is and where it is coming from.


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Any suggestions for me? I too have discovered a leak and I'm trying to figure out how bad it is and where it is coming from.
If it's coming from your weep hole, then your water pump is the issue, or on its way out. . .my leaks came from hose clamps that had loosened over the years. . Specifically the one that connects to the upper right side of the thermostat housing. .and would travel through that s channel you see between the water pump cover and the crank case.

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Classic leak from the vee above the engine block. The water pump cover bolts to the block and leaves a channel between the cover and the block to drain leaks from above the engine. The coolant runs down and out the lower part of the channel below the water pump (at upper red arrow in pic with two arrows) and out the square opening near the round water pump weep hole. Mixed with dirt and road grime it appears oily in nature but it is coolant. If you pull the radiator I think you will see evidence of leaks from the thermostat housing O ring and the hoses that connect to the t-stat housing. Those leaks stand on the top of the motor then drain down the channel to exit on the right front and right side of the engine.

The fix is to snug up all the clamps you can get to with a 6 mm flexible nut driver and long screwdriver and replace the t-stat housing O-ring. Many owners also replace the OEM clamps with constant tension clamps. I did not go that route and fixed this problem with carefully snugging up clamps at 86,000 miles.
 
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Classic leak from the vee above the engine block. The water pump cover bolts to the block and leaves a channel between the cover and the block to drain leaks from above the engine. The coolant runs down and out the lower part of the channel below the water pump (at upper red arrow in pic with two arrows) and out the square opening near the round water pump weep hole. Mixed with dirt and road grime it appears oily in nature but it is coolant. If you pull the radiator I think you will see evidence of leaks from the thermostat housing O ring and the hoses that connect to the t-stat housing. Those leaks stand on the top of the motor then drain down the channel to exit on the right front and right side of the engine.

The fix is to snug up all the clamps you can get to with a 6 mm flexible nut driver and long screwdriver and replace the t-stat housing O-ring. Many owners also replace the OEM clamps with constant tension clamps. I did not go that route and fixed this problem with carefully snugging up clamps at 86,000 miles.
I stuck a scope above the engine block and sure enough just like you said there was a little puddle of coolant. Thanks now I know where to focus my energy!


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I have a similar problem on my 82,000 mile 2002 ST1300A. I have replaced the O ring seal and still have the leak but notice that the o ring is not a good snug fit in the grooe of the water pump cover. This makes it easy for the O ring to displace during refitting of the cover. Today I enquired of David Silver U.K as to whether the early ST1300 O ring has a different part number and was quoted a different one to that ordered/ I recently replaced. The early part number is 19226 MCS 000 compared to the one I fitted earlier of 19226MCSA10 which looked the same as the 1st I replaced which was not a good fit either. That probably wasn't the original as the bike has had a clutch change in prior ownership. Any thoughts please?
 
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