Oldsmobile 1999 Intrigue - Manual (Page 270)

yellow blue
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Checking Coolant (3.5L V6 Engine)
The coolant surge tank for the 3.5L V6 engine is located
in the engine compartment toward the rear of the engine
on the passengers’ side of the vehicle.
CAUTION:
Turning the surge tank pressure cap when the
engine and radiator are hot can allow steam and
scalding liquids to blow out and burn you badly.
Never turn the surge tank pressure cap
-- even a
little -- when the engine and radiator are hot.
The vehicle must be on a level surface. When your
engine is cold, the coolant level should be at the
FULL COLD mark.
If the low coolant warning
light comes on and stays on,
it means you’re low on
engine coolant.