Compression in cooling

[Djdawson2 at aol.com]

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Anyone ever run into or had any BTDT with compression in the cooling system.
I just took my first long trip in the 20v, and had a less than good time
during the last 10% of the trip.  Somehow exessive pressure is building in
the cooling system which first blew the cap off the overflow tank, then blew
the radiator end cap, finally blew the end off of the electric coolant pump.
The source of the pressure appears to be compression.
Has anyone out there experianced this?  Is it generally a blown head gasket,
or is head cracking common?
As always, any help greatly appreciated.
Thanks,
Dave