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Hi all,

Been getting ready for the next riding season and I have found a tricky coolant leak. This engine was 100% rebuild and ran for the first time last May. It never had a problem all of last year. This spring after the first ride I noticed a few drops on the floor. I cleaned up the area around the water pump housing and checked the bolts. Snugged one of them up a bit, but not much.

Started the bike and warmed it up. Stayed dry, so I shut it down and parked it. The next day I see a bit of green at the water pump weep hole.

It's hard to see around the housing, but I think it's at the weep hole only... which means the mechanical seal is the culprit.

I know these are notorious for leaks, but it ran all last year. It was brand new seal assembly form Kawasaki.

Before I start taking things apart for inspection, I'm curious what you guys think.

Off the top of my head Tyler, I would say it's not uncommon for a minor leak from the seal when the bike sits for 5 months over winter and the fact that you mention that it leaks overnight is a dead ringer for a mechanical seal leak. When the bike is hot and the coolant system is pressurized, the coolant pressure forces the seal faces together slightly. Mechanical seals are usually pressure balanced between atmosphere and system pressure otherwise the excess force in the coolant system would force the seals too hard and wear out the seal faces.
The static seal face is usually stellite and proned to oxidation if the coolant is off in PH. Sometimes the surface oxidation will wear off if it's really light but then again the rotating carbon face will take a hit in the process.
In the Nuclear plant we used to reface the mechanical seals all the time. You need a lapping machine with a diamond compound to dress up the stellite face and a surface plate (or you can substitute a piece of 1/4" glass pane believe it or not) with 2000 wet and dry to reface the carbon seal. If you had the equipment, it's a 15 minute job to reface the seals plus the remove and replace. A refaced seal is withing 2 to 3 lightbands which is down in the millionths of an inch.
I would give it maybe an hour's worth of running time and see if it sorts itself out. I'd also check the PH of the coolant or just repalce the coolant.
Hope this helps
KB

Well a good long drive did the trick. I took the bike out on the highway for good run. Checked a few hours later and no leaks. Had a couple other short rides and no issues now.

I had considered running a waterless coolant, maybe that would help keep things is better shape for the long run.

Anyone here run waterless stuff in their bikes?

Tyler wrote: Well a good long drive did the trick. I took the bike out on the highway for good run. Checked a few hours later and no leaks. Had a couple other short rides and no issues now.

I had considered running a waterless coolant, maybe that would help keep things is better shape for the long run.

Anyone here run waterless stuff in their bikes?

The waterless coolants are almost 90% Ethylene or Propylene Glycol. They have very poor heat transfer capability due to their specific heat capacity. This results in an inability to transfer heat efficiently from the engine, and also dissipate that heat via the radiator. Yes, it won't boil as easily (197 degrees C verses 100 degrees C at sea level) but your engine will run even hotter than it will on a 50/50 mix, it's just that you won't see it boiling over. Your temperature gauge will show it is running hotter too. If your system is in good serviceable condition you shouldn't be suffering from over heating problems. Things to check, flow (pump and blockages), fluid level, thermostat and radiator cap. The cap is designed to allow the thermal expansion of the fluid to build pressure thus increasing the boiling point of the coolant. If it's not doing its job your system pressure can't build and it will boil at a lower temperature. The reason none of the vehicle manufacturers will endorse waterless coolants (read Evans) is because they understand physics.