coolant leak!

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At the end of last season (chicago), i noticed a very small pool of coolant... :( Oh well.. about 65k on 1999. I'm trying to track down where it's coming from. The pool is centered under block.Ive read about pump, hoses and a lol plastic joint that's prom to failing. Plastic is off bike, and it only happens after cooling from warmed up condition, so right now I know it's small...
 
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Commonly found to be coming from loose hose clamps on the hoses buried in the engine V, when the drips are coming from the rear of the engine. Also common for the overflow hose to develop a split where it connects to the thermostat housing/rad cap area. Is the overflow bottle full? That would indicate a split as mentioned.
 

Erdoc48

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One of the more common areas of a leak is the under the carb bank hoses and the aluminum joint where they attach to the head. The aluminum elbows can rot and crack as well as have an O ring seal failure. Also, the hoses are exposed to a lot of heat that can cause failure. It could be a relatively minor leak but you don’t want to have a more major failure when on a longer ride away from home. There are some very good write ups here on how to do the work and I’ve completed the work on each of my 2 STs in the past few months (never did it before and found it all pretty intuitive). It’s actually pretty straightforward if you take your time and are willing to do a little disassembly - if you choose to do the work yourself, I would get all the parts together before doing anything (new hoses, elbows, O rings, etc.). Also, just for completeness, it can be the overflow tube as it tends to get a little dry and brittle vs the bike needing a new radiator cap. Does it run hot? A thermostat could be faulty if that’s the case.

If you need it, I can look up my Partzilla list of the pieces I bought when I overhauled my STs

Edit...here’s the list:

Order Items
Ordered Shipped Total Price
16211-MT3-000 - INSULATOR, CARB
8 8 $70.72
19503-MT3-000 - HOSE, RADIATOR
2 2 $24.06
19504-MT3-000 - HOSE, L. THERMOSTAT
2 2 $35.64
19505-MT3-000 - HOSE B, WATER
2 2 $23.68
19506-MT3-000 - HOSE, R. THERMOSTAT
2 2 $30.00
19523-MT3-000 - JOINT, WATER
4 4 $33.32
91331-PC9-003 - O-RING (21.2X2.4)
4

Remember, the above is for 2 bikes. Also, I got some 1/4” fuel line for the overflow hose from a local Advance Auto parts, so no need to get this from Partzilla.
 
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thanks for the info!! I'll inspect around the overflow.. If it is prings or hoses I'm thinking about jus replacing ALL! prob even the pump just for Peace of mind on long trips! I dont have a prob doimg it myself although i have read some hos kits dont quite fit.
 
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leak is under engine, centered, kinda around oil plug. but haven't seen it drop yet
 
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leak is under engine, centered, kinda around oil plug. but haven't seen it drop yet
That could indicate a leaking water pump seal. It wouldn't be a major leak from there, but you can usually trace the dried coolant back up on the front of the engine. The use of a coolant that contained silicates (cleaning agent) can damage that seal. A leak from the V of the engine will normally fall off the rear of the engine, not near the oil drain plug.
 
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Interesting idea. How often would the pump seal be expected to leak at 65K miles?
Using the proper coolant, one would never expect to see that pump fail at 65K miles, but I, unfortunately, speak from experience.

On my previous '95 model, bought new and when I was uneducated about the contents of coolant, I used a regular auto store coolant that required me to add the distilled water 50/50. That was after four years and about 30,000 miles. Changed it again three years later and at 55,000 miles, with the same stuff, since a gallon jug goes a long way!

A year and a half later and about 60,000 miles, the pump was leaking. Then I found out, on a forum, about the silicates in some coolants and the danger they posed. Using Honda Type 2 ever since.
 
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Agree with Bush, the hose leaks from the engine V drip well to the rear of the engine, oil drain plug area is something else.

But, if you're riding a '99 that's never had the hoses in the V replaced, its time to do it, they're just waiting to split. When the hoses fail they split along the length of the hose and your coolant blows out almost instantly and leaves you stranded.
 
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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!
 

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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.
 
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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.
 
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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.
 
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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?
 
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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.
 
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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.
 
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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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