1970 Cadillac Eldorado coolant overflow

I've got a 1970 Cadillac Eldorado, about 58K miles.

When driving it, it's fine.
Sometimes after a ride I stop the car and the plastic coolant tank
(outflow hose) will overflow and spill some coolant onto the street.
This never happens WHILE the car is in motion, and I can always
start it up again and drive it if I want to right away.

I heard a gurgling noise when I had the hood open once when I
tried to diagnose it. Came from the middle-to-back of the engine
compartment on the left side, then through the tube and then ..
no surpise ... coolant surges into and overflows the tank.
Anyone have any ideas why this happens? I have not added
or removed any coolant recently. And I've not seen any coolant on
the street before this either.

Is this simply a thermostat problem? Do I need to replace it?
Thanks in advance for any ideas on this.

"The Derfer" > wrote in message
...
> I've got a 1970 Cadillac Eldorado, about 58K miles.
>
> When driving it, it's fine.
> Sometimes after a ride I stop the car and the plastic coolant tank
> (outflow hose) will overflow and spill some coolant onto the street.
> This never happens WHILE the car is in motion, and I can always
> start it up again and drive it if I want to right away.
>
> I heard a gurgling noise when I had the hood open once when I
> tried to diagnose it. Came from the middle-to-back of the engine
> compartment on the left side, then through the tube and then ..
> no surpise ... coolant surges into and overflows the tank.
> Anyone have any ideas why this happens? I have not added
> or removed any coolant recently. And I've not seen any coolant on
> the street before this either.
>
> Is this simply a thermostat problem? Do I need to replace it?
> Thanks in advance for any ideas on this.



Having had one of those BEASTS, I'd suggest you take it in and get a
power flush. There is probably scale all over the cooling system. Is that
the original block or has it been rebuilt? You can check the thermostat too.
Also the radiator cap. Do a pressure test. That engine is very sensitive to
having the right pressure. If there is any leak it will boil. Mine was a
royal pain in the ass after the car was 2 years old.