4000Q overheat at high speeds

[Suffolk GameServer LAN]

Radiator or thermostat. BUT: my guess is that at your age/mileage and A/C
and high speed 70 Plus your at the limit of output of the once 110 HP motor.
That's why it otherwise runs "cool as a cucumber"

Or could it be a crappy oil filter? Maybe the radiator level is down?

In my past reflections:  The 4000Q wizzed up and down hills at 80 but when I
went to "floor" it: I realized I was already 1 inch from the floorboards.
New 110HP - today????????????
On my 4000Q (which I drove today for 1 mile / first time in 13 months w/
400K the braided expansion tank hose was "Steaming" from the release of hot
water vapor through its now pourous skin.  Just an observation.
HTH -Scott in BOSTON

Again, it only overheats when driving for 15 mins or more, at greater
than 70mph, when outside temps are 90+.  It does this whether or not the
A/C is on.

It runs cool as a cucumber when the A/C is on high and I'm stuck in
traffic, driving in the city, or crusing at only 60mph, even when
outside temps are 100+ degrees.