I'm fed up with my ST dripping coolant when I start it up, so I've decided it's time to hit the war path and get rid of it.
I think we've got
two enemiesone enemy here: vibration of the free-floating thermostat housing compounded bypoor clamping.
I explored ways to get the thermostat solidly bolted to the engine and didn't come up with anything useful. The closest thing to a real solution I could come up with was fabricating a bracket that bolts on with the hangar bracket on one end and connects to the housing between the housing's bolt heads and the housing itself at the other. I didn't find that a good place to start because the bracket would be difficult to fabricate, to reach around to the hanger bolts. Alternately, the bracket could be welded to a replacement hanger ($10), but I'm not sure what welding would do to its strength. I'd probably have to spec out longer bolts to hold the bracket and the thermostat housing together.
That leaves the clamps, for which I think there's help.
From what I've been able to learn so far, the worm gear clamps being used to secure the hoses are a large chunk of the problem. The perforations in the clamps allow what's called extrusion of the hose, the result of which is a loss of clamping torque. One manufacturer says that loss can be as much as 80%, which I suspect is a bit of an exaggeration given that the perforations don't make up 80% of the surface of the band. I think that, combined with the differing expansion rates of the aluminum and steel in the fittings and the shaking the whole free-floating thermostat housing gets are keeping the clamps from sealing and staying sealed. Two solutions look good:
The one that looks the best from a mechanical standpoint are the Gates PowerGrip SB clamps. These are thermoplastic bands that attach to the hose and are shrunk to size over both sides of the bead in the fitting. Gates claims they contract as they get colder, maintaining a tight seal. They'd be impossible to replace on the road without carrying spares and require a $50 tool to remove. I'll pass.
The next best thing is a constant-torque hose clamp, which adjusts itself with temperature to maintain a good seal. Breeze Industrial makes a model that looks like it will fit the bill. Gates makes something similar, but I wasn't able to find any information on them.
The Breeze clamps come in sizes that can replace the #6 and #17 parts (see the attached drawing), but I'm not sure what size the #10 and #12 parts are. So if someone has that part of the system apart, I'd appreciate a measurement on the outside diameter of those hoses so can track down the right parts. Once I have everything I need, I'll do the replacement next time I strip the bike down and report on how it all did over the course of next winter.
Updates and Other Info
The clamps are Breeze P/N CT-9412 and are available from:
- McMaster-Carr as P/N 54205K13.
- NAPA auto parts stores as P/N 705-1502
The torque for these clamps is 45 inch-pounds. Make sure they're torqued correctly or they won't work.
Fall, 2009: I got the last of the clamps replaced this spring and had had no leakage so far. This has included a number of very cold mornings, when the bike is prone to it.
Spring, 2010: Still no leaks, even after a long, cold winter in the garage.
Fall, 2012: Still no leaks.
Spring, 2014: Not a leak in sight.
The five clamps that need to be replaced are highlighted in this photo: