It's my 2010 Vespa GTS 300 i.e. It has just over 50,000 kilometers on the odometer.
Can a Vespa rise from the dead?
Is it possible for a blown head gasket, something akin to a brain aneurysm, to heal spontaneously?
If not, was the gasket in fact blown?
And if not, whence the coolant leak?
So many questions. For the time being no satisfactory answer.
Here are the facts as I know them. I need your insight.
After a long day's ride from State College to Niagara falls, some 370 kilometers, a coolant leak in the engine compartment brought the day's ride to an abrupt end.
Other symptoms: when I opened the saddle to refuel, steam was rising from the engine compartment. When I removed the underseat bucket to reveal the engine, there was coolant everywhere, as if there was a spraying coolant leak. The underside of the seat compartment bucket was wet. When I started the bike with the bucket out, the coolant was dripping from the stand below the motor, but there was no evidence of a leak seen from above the engine.
That's all I've got.
The Vespa completed its trip on a flatbed, ending up at Vespa Toronto West. Lou Dibiase, whom I trust, diagnosed a blown head gasket. More spefically, a blown lower head gasket, the one that's between the two halves of the engine, I think. That seemed like a reasonable diagnosis.
Last week I needed to get my bike down from its P1 parking spot to a temporary spot on P3 because the P1 level was being pressure washed.
I refilled the cooling system with tap water, up to the lower fill mark on the reservoir. I fully expected to see the water begin dripping down the stand. But there was no leak. I started the motor. Still no leak. I left the motor running until the bike reached normal operating temperature. Still no leak.
I rode down to P3. Still no leak.
Two days later I checked on the bike before riding back up to P1. Yup, still dry.
I discussed the situation with my friend Ed Thomas, a very experienced motorcycle mechanic. Ed thought that perhaps the water was now leaking into the oil pan via the blown gasket rather than leaking to the outside. He suggested checking the coolant level in the reservoir, and checking the oil level. If both were at their normal levels, it would be reasonable to conclude that the coolant wasn't leaking into the oil. I checked and the levels were normal.
Today I decided I would hop on the Vespa to run a few errands and eventually make my way over to Ed's workshop, to talk, well... talk shop, and zombie Vespas. You guessed it, still no evidence of any leak. That, and I kept an eagle-eye on the instrument panel: the engine temperature remained normal the whole way. The check engine light lit up a couple of times, but reset itself with an engine restart. That happened three times on the way to Ed's, each time shortly after one of my little errand stops. It never happened on the way home. That was a 30 kilometer return trip, all on city streets, no expressways.
Ed's as stumped as I am.
The only other thing I can think of, is that close to the Pennsylvania New York border, I refueled at a tiny country gas station, and I realized that the helpful attendant handed me a nozzle switched to regular gasoline with ethanol. I only realized it had happened further down the road when the engine started stumbling slightly. Three tanks of 91 octane fuel later, the performance symptoms disappeared. I don't think that's relevant. I just mention it because it's the only other engine-related issue that occured on the trip.
So there you have it. The Vespa seems for all the world to be running like a top. Or at least running as well as it did when I set out for the wilds of Pennsylvania.
What is your take on this little Italian mechanical mystery?
Is there any chance that the coolant leak might have come from the coolant bleed valve at the top of the engine rather than from a head gasket leak?
Can a blown gasket heal itself?
Should I overhaul the engine on the assumption that there is a defective gasket?
What would you do?
Like I said, I am stumped.
Thanks for reading.