My '87 likes to barf out its coolant little by little through the pressure
cap into the overflow tank to the point where the damnable blinking light
forever torments me.  But, the light is the least of my worries as
eventually even the overflow tank will overflow to the point where I am
losing coolant.  This usually happens when I've been working the van hard
like driving all day or up long hills, etc. but even around town on a daily
basis, the coolant will barf out into the overflow (causing the low coolant
blink-blink) only to be sucked in later over-night.  I understand that this
exchange between tanks is normal, but not to the extremes I'm seeing.

I've replaced the pressure cap, and although happening less often, the
problem still exists.  I've had the entire cooling system flushed and
inspected (not my work), the radiator thermo-switch/fan works fine, I've had
hoses replaced where needed, I've bled it myself, have new coolant (50/50),
new thermostat, and a new pressure cap on that stupid tank where the
blinking-light-sensor is.  And, yes, I've adjusted the coolant levels to the
marks indicated on the tanks.

Has anybody had similar experience?  My guess is that the pressure in my
cooling system exceeds the rating of the cap under load, and eventually
allows the coolant to expand and boil over.  That tells me that I've got
restricted flow somewhere.  If it isn't a thermostat failing to open all the
way, then it's probably my radiator.  Any other advice?

Thanks,
Brian

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