At 01:36 AM 6/23/2002 -0400, you wrote:
>The car runs cool all day long around town but after about an hour on the
>hiway it starts to overheat. The only thing left that I know of that
>could cause the problem is crud in the block. I have been told that one
>could pull the freeze plugs and clean it all out but don't know if it is
>true or not.
Steve, I am having a similar problem with my 68 sedan. As you start
driving on a prolonged highway drive, the rust particles slowly come up in
solution to the coolant and reduce its heat transfer effectiveness. One of
the things to try as a temporary solution is flush the system right after
an overheated ride. This way, the rust still in solution will come out
with the drained coolant. You may have to do this many many times before
some improvement is finally achieved, and I do not think this will ever
lead to a complete problem elimination. But it helps. What I have done on
my sedan is the following. I installed a motorcycle radiator behind the
grill (I think from a BMW) and connected it with heater hoses and valves to
the heater circuit. In the summer, I turn off the heater valve (no coolant
flow through the heater core) and turn on the "auxiliary radiator" valve
for a bit of extra cooling capacity. That seems to "cure" the problem,
since the temperature will never exceed 200-210F, unless I have not flushed
the radiator for many-many months. Also, recently my vacuum advance
appeared to have stopped advancing, which explains my slightly higher
temperatures this summer.
D^2
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