Water pump leak?

David P

David P

Joined
Oct 4, 2007
Messages
83
Location
Tampa, FL
Bike
ST1300
Last spring I was losing coolant monthly. As part of the troubleshooting, I took off the radiator and tightened all hose clamps near the thermostat: they were loose and there was evidence of leakage. I figured that this solved my coolant leakage problem.

Flash forward to today: I just did the 60k maintenance on my 2003 ST1300A. The reserve coolant tank was at the low level - I had filled it at the 56k maintenance interval. Over the last few months I've occasionally smelled coolant at stoplights, particularly when the fans come on. I've attached pictures of the front of the engine casing.

My questions:
1. Should I retighten the hose clamps?
2. What about replacing all hose clamps with aftermarket items?
2. Do I need to replace the water pump mechanical seal?
3. If #2 is true, do I really need the special equipment listed in the service manual?
 

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Hose clamps are always a problem on the STs. There are lots of threads here on coolant leaks and suggestions of replacing the clamps with constant torque clamps to eliminate them loosening up.

Lots of stuff to read in this part of the forum. Tech Forum
 
David P said:
Last spring I was losing coolant monthly. As part of the troubleshooting, I took off the radiator and tightened all hose clamps near the thermostat: they were loose and there was evidence of leakage. I figured that this solved my coolant leakage problem.

Flash forward to today: I just did the 60k maintenance on my 2003 ST1300A. The reserve coolant tank was at the low level - I had filled it at the 56k maintenance interval. Over the last few months I've occasionally smelled coolant at stoplights, particularly when the fans come on. I've attached pictures of the front of the engine casing.

My questions:
1. Should I retighten the hose clamps?
2. What about replacing all hose clamps with aftermarket items?
2. Do I need to replace the water pump mechanical seal?
3. If #2 is true, do I really need the special equipment listed in the service manual?
Click to expand...

Run the bike until the fans come on and watch the round weep hole just above the square hole. Watch closly for eather coolant or oil or both to leak out of the round weep hole. If leaking then the seals need to be replace. If not than OK. If fluid comes out of the square hole than there is leakage from above in the V, or the pump cover o-ring is leaking. The most critical part is pressing the parts into the clutch cover. You can take the parts down to the dealer and have them press it in.
 
I would pull the radiator and look for evidence of leakage from the hoses and thermostat housing in the vee between the cylinders. You cleaned the area around and below the square weep hole but it is still evident you have had leaking coolant running down from above. Leaking from the square hole is coming from a source external to the water pump, leakage from the small round hole is coming from the inside of the water pump. It might be leaking there but it is obvious that alot is coming down from above the water pump.

I had found weeping around or from round weep hole about 1500 miles ago. I thought it was oily residue because it was black from road grime although there was also evidence like yours it was coolant although it never leaked onto the garage floor. I cleaned the area when I first found it a few weeks back(86,000 miles, it was clean when last exposed at 65,000 miles) and unwittingly removed the evidence to tell for sure if the water pump seals were weeping or something above that was leaking. The level of the overflow tank was halfway down from the upper to the lower mark after 21,000 miles so the leak was not bad. Last week I removed the tupperware to start a fix wherever it lead me. In a way I was relieved to find the small round hole clean and dry and the leaking was coming from a few of the hose clamps and the thermostat housing cover O-ring. The same grimy residue mixed with the blueish green crud from baked-on coolant was coating the underside of the thermostat housing and was on top of the water pump under the housing. No water pump rebuild yet. I was able to get to all but one clamp and that one had no evidence of leaking. The others I tightened and replaced the O-ring. I bought a long 6 mm open end wrench to reach a few of the clamp screws that were oriented vertically and a 6 mm 1/4" socket on an extension fit the others with the screw head oriented in the horizontal. The one I could not reach was way back on the port side. They will probably leak again but I'll go there at that time.

I long ago quit cleaning the front of the engine by removing the fairing to get to it but going forward I am going to do this on a regular basis so I will be able to spot leaks on the front and side of the clutch housing which I can see thru the cowl behind the front wheel. By getting down on my knees I can also peer up and forward near the oil level window and just see the weep holes. I am going to monitor more closely but not worry about a pump rebuild until it needs it.
 
In the past I've had significant leakage around the hose clamps near the thermostat. Tightening them seemed to stop the leak. However now it seems to be leaking from the water pump housing. I wiped clean the round weep hole before the pictures were taken; it was oily but there wasn't any dried coolant underneath it. The coolant crud seems to be coming from under the casing, like the case gasket has failed. Has anyone seen this occur?
 
David P said:
In the past I've had significant leakage around the hose clamps near the thermostat.
Click to expand...

You've probably got it in the present, too.

There's a drain point in the vee that prevents anything that leaks up there from pooling and running into the alternator. That drain point empties into a channel behind the water pump cover, and that channel ends just above the clutch cover. The pattern of the coolant streaks in your pictures is inconsistent with a seal failure, and while it could be a gasket failure, the chances are much better that your clamps have lost torque and leaked again. BTDT, replaced mine with constant-torque types and haven't had a leak since.

--Mark
 
No one shout at me but on determining a leaky hose in the "V" (leaks from the square hole) as being the cause of my slowly dipping water levels over 2-years (50000+ miles) and with no hope of getting the time to dig in and fix it, I poured Radweld in on a fluid change and a whim.

All indications are that the leak is no worse: I'd hesitate to claim otherwise, but there's no evidence of further leaking at this time.
:run1:​
 
I don't know about the Radweld but it sounds like another trip into the bike, this time to change hose clamps. I'll report back when I open up the plastic and get to the hoses. Thanks for everyone's help. DP
 
David P, in the third picture I see what looks like an elbow coming out of the the top of the water pump cover that is D-shaped or oblong shaped. Although it doesn't look like it's leaking, sealing a non-round fitting has to be difficult. I don't have any leaks on my bike (to my knowledge) but I'm wondering if all the bikes have that upper hose fitting over a flattened elbow???
 
I did a write up a while back (in the known issues category) with similar looking pics as yours, it was the hoses in the "V" that were leaking. Hose clamps lost torque, I had to remove the throttle body to replace the clamps with the constant torque type. No leaks since. It was quit a project though.
 
I was talking with a Honda service tech yesterday about the leaks that I had found and he mentioned that what he does that helps prevent recurring leaks in this area is to remove the hose from the fitting and clean the crud off off the ID of the hose and OD of the fitting it goes over rather than just tighten the clamp more. This might or might not be of help.
 
That will help until the clamp loses torque and coolant seeps through, creating more crud.

--Mark
 
Anyone know the number of hose clamps and their sizes in the throttle body area (or a link to an existing thread)? I'd rather have these items on-hand before I commence a bike teardown. [No bike = no wheels]

Disregard - a little research goes a long way.
 
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It is curious why clamps and hoses don't leak on cars after a few years and 100,000 miles or more. If they are screw clamps they are more or less the same clamp on the same type of hose. My ST didn't leak, at least noticably, from 23,000 miles to +/- 73,000 miles, about 50,000 miles there.
 
Cars have been using spring-type clamps for a very long time. Not only are they less expensive and less work to install, they also self-adjust. My theory about why this is a problem on the ST is that the clamps are steel and the fittings are aluminum, which has a much higher coefficient of expansion. When the bike gets cold enough, the fitting shrinks faster than the clamp. The clamp loses clamping force, which is one of the things keeping the worm gear in place. Rayzerman, who's been in the auto business, also says they dump a stop-leak pellet into the cooling systems on cars during manufacturing. Cars that were old enough to have had worm-gear clamps would also have had steel fittings that wouldn't have shrunk as quickly.

--Mark
 
The difference in expansion makes sense, yet the clamps on the radiator ends don't seem to have the problem and those fittings are aluminum. Maybe the heat build up in the vee is a factor.
 
If anything, I think heat buildup cures it because my bike only ever leaked when it was dead cold and the cooling system was in bypass. Once it warmed up, it stopped and wouldn't leak again until the next morning.

Sometime when I feel like doing the math I'll have to take a rough cut at what the difference in the fitting and clamp diameters would be between operating and ambient.

--Mark
 
David P, mine also leaks at a couple hose connections under the throttle bodies. There's often the smell of coolant and the occasional streaks seen from the square drain hole by the water pump.

These pictures were taken a year apart on mine, the first one in 2008 prior to going in and servicing it (including tightening the aforementioned hose clamps), and the second a year later, showing that I'd significantly decreased the leaks but not solved them:
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Here's a photo of one of those pesky leaks taken from above the throttle bodies, as seen through a small mirror.
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My expectation is that you'll find the same thing. I have just purchased constant tension hose clamps (McMaster-Carr P/N 54205K13) in hopes of solving the issue, but have not decided when to open her up.

What coolant is in your bike now? Based on the buildup of scale in your pics, either you're using a silicate-based coolant (a no-no in aluminum engines) or yours is leaking quite a bit (don't delay in repairing it). Just my opinion.
FYI: http://pages.infinit.net/mcrides/engine_tech/engine_coolant.htm
 
Good eye Scott. It has a very light oily residue--I've been keeping an eye on it since it was new (I haven't wiped it off that I can recall).
:shrug2:
 
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