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Display Mesage #94002


Bubble, Bubble, Toil and Trouble
Written by russelljpt on 6/11/2010 at 04:36 pm

This sounds suspiciously reminiscent of a mysterious problem my '89 had. The
temp gauge would act normally until I had ridden about 50 miles, or sooner if
uphill, and then would quickly move to the hot end, and occasionally peg.
Coolant in the overflow tank would boil, or nearly. And the fan would not turn
on. Only fix was to park it for 30 minutes, and repeat. Slowed down one trip
quite a bit. I replaced the pressure cap, thermostat (which had nearly
disintegrated), and coolant, to no effect. I installed a manual override to the
fan circuit, so I could make it run all the time. Minor effect. The problem
turned out to be a slightly blown head gasket that apparently sealed OK until
the engine got thoroughly hot, and then leaked exhaust gases into the coolant.
I am guessing that the reason the fan failed to activate was that the leaking
hot exhaust gas quickly overheated only the coolant in the top of the system,
and the fan switch, near the bottom of the radiator, did not get the message.
Maybe someone else has a better answer? The (expensive) fix was to rebuild the
engine, including first overbore and new pistons and rings. Cost $1300 in
January, when the shop was hungry. The good news is that not only is the
overheating problem definitively fixed, but the engine is WAY more powerful and
rideable than it was before (70K miles), at least a 20% difference as measured
by the seat-of-pants method. Also gets better mileage.

Jim Russell
Seattle
'89 Great White

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