Coolant pipe seepage

This has probably been discussed here before, but since Ponch mentioned this problem, I decided to discuss it here. (This essay is re-posted in-part from my thread "Nomad Blogging Continues" in the Custom/Cruiser room over at the motorcycle-usa.com forums. All my other mods and maintenance are recorded there in extensive detail in case anybody wants to read themself to sleep.)
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Day 1465
27,881 miles

This was one of my reservations about buying a liquid cooled bike, and unfortunately while the Nomad has a pretty solid cooling system it has one weak spot that is the result of poor design. Fortunately it can be fixed cheaply. Unfortunately it's a pain to do.

The issue is the coolant pipe going into the top of each head, which connects the radiator hoses to the heads. These are short steel tubes with a single o-ring on the end which plug into a hole bored into the top of the head. They are retained by a single small bolt each, which connects a tab (welded to the steel pipe) to the head.

Unfortunately, as the cylinders vibrate up and down on this big v-twin, they are shaking that pipe in and out of it's bore just a little, and the o-rings eventually (quite quickly in fact) wear down and start to seep coolant. The little tab and bolt arrangement is not in line with this motion, but transverse to it, and simply does not do enough to restrain the coolant pipe firmly.

My solution: a new o-ring and silicone glue.

...This seepage is very minor, and some owners may never even notice it. I typically have been adding only about 8 ounces of coolant per year to this bike. That tiny amount of seepage evaporates from a hot engine before ever hitting the ground, nor even any place on the engine where it becomes easily visible.

This is part of what makes it a bear to repair: it's burried under a lot of junk and takes lots of effort to get to. I had to remove the windshield, gage trim. gages, seat, and gas tank. Removing the gast tank involves unplugging two very reluctant electrical connectors to the gages and fuel level float, and the detachment of 6 hoses on the fuel system: two vent hoses, an overflow hose, a vapor recovery hose, the fuel return hose, and the main fuel hose to the injectors.

Four of those hoses are under the tank, and I needed a friend to hold the tank a few inches above the frame for five minutes so I could detatch them. They don't give you a lot of slack to work with. Have a rubber cap ready to cap off the gas when you detatch the main fuel hose, as it will leak quite a bit if you don't. ... I also took pains to run the tank almost dry the day before, so my friend wouldn't have to struggle with it.

Once the tank was off I drained the cooling system, (the plug is under the radiator) removed the pressure cap (under the gas tank) and removed the first upper coolant hose from its pipe. Getting to the retaining bolt on the rear coolant pipe was pretty difficult. It requires a long skinny 8mm wrench and a lot of patience. It will not unscrew completely from the head as it hits the throttle mechanism, which is not removed without removing the air filters, backing plates, associated plumbing, and the fuel injectors and intake manifold. This I was NOT going to do. I removed the retainer bolt as far as possible, and bent the tab on the coolant pipe a little until I could get it loose.

The pipe required serious persuasion with some long long-nosed pliers, and in the process I nicked up the hose-mating surface a little. I burnished both ends off well with a powered wire brush, removed the burrs I'd made, straightened the tab I'd bent and trimmed it a little so it could go back on straight with no monkey business. I cleaned it up with solvent and put it aside.

I then cleaned the bore in the head out with solvent and a rod I made similar to one for cleaning shotguns with a patch. I scrubbed it really clean (multiple times) so the silicone would stick, finally wiping with dry paper towels. I mounted a new o-ring to the pipe with silicone, slathered on some more silicone (Permatex black label BTW) and shoved it gently back in. I pressed it into the head while my friend struggled to re-tighten the captive bolt. I let the glue set up a while and took a break.

Once the silicone had time to set, I cleaned the end of the coolant hose inside, put some Permatex (orange label) weatherstrip advesive in the end of the hose and clamped it back in place. I let that set up a bit.

(Repeat on the front head, where the bolt is easier to remove, but the hole is harder to clean.)

Becuase I did not want to run the engine until the silicone had set over night, I was very careful to get out as much air from the system as possible when re-filling it. I wiggled and pinched hoses and rocked the bike side-to-side and back & forth until I managed to get nearly 3 quarts of HondaCool into it, then capped it off. Any extra air will blow out into the surge tank tomorrow, and be replaced by coolant siphoning back when the bike cools off tomorrow night. I hope. (It did.)
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I'll post a little sketch of the offensive coolant pipe design in a bit.

Cadd.