haynes repair manual saab 9-3

Coolant loss Saab 9-5 Workshop dismantling the grill/bumper/headlight just to look! I cannot find any mention of a pressure release valve in the Haynes Manual but surely there must be one? The yellow reservoir cap doesn't appear to have any pressure release system. Would be grateul for any ideas please ... Saabs: 2001 9-3, auto. 2001 9-5 SE V-6.
haynes repair manual saab 9-3
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