How long for the engine to cool

I have to replace a leaking heater control valve in the XJ after a 15:00 minute drive home from work. How long does it take the engine to cool? Thanks in advance.

pop the hood and give it 20 minutes or so, just open the radiator cap slowly with a rag over your hand, it should be plenty cool enough to work on by then.

GrimmJeeper said:

pop the hood and give it 20 minutes or so, just open the radiator cap slowly with a rag over your hand, it should be plenty cool enough to work on by then.

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...said the guy with the burned arm.

...but he's right. Just expect things to be a bit toasty even then. Have a hose handy to cool things off even faster. Once the pressure is relieved it should be easy working up top like that. Be careful.