[Grammar] Which tense to use after "should"?

[gjakupan]

Please tell me if this sentance is correct:
"The cooling water should circulate for minimum 20 minutes after the engine has been stopped."

Is it better:
"The cooling water should circulate for minimum 20 minutes after the engine had been stopped."

Or can it be:
"The cooling water should circulate for minimum 20 minutes after the engine was stopped."

I'm confused what tense should I use in this form of advice...

 

[e2e4]

A learner

I see the examples this way below

The cooling water should circulate for a minimum of 20 minutes after the engine is stopped. (advice, procedure)

The cooling water should have been circulated for a minimum of 20 minutes after the engine had been stopped.(But it didn't happen, the engine broke.)

The cooling water had to circulate for a minimum of 20 minutes after the engine was stopped. (reality, it worked that way, the event happened)

 

[gabber]

"should" is a modal auxiliary verb, and after a modal auxiiary one alway uses a bare infinitive:
"should I be quiet?" "he should leave now" "this should be the place"...

 

[Pedroski]

"The cooling water should circulate for (a) minimum (of) 20 minutes after the engine has been stopped."

is correct, because 'should' indicates a possibility, something that has not yet happened. Nor has the engine stopped. So use 'has' not 'had been'. Think of it like this:

If the engine has been stopped, then the water should circulate for 20 minutes afterwards.
Anytime the engine stops, then the water ... blabla.

"The cooling water should circulate for minimum 20 minutes after the engine had been stopped." Bad

"The cooling water should have circulated for a minimum of 20 minutes after the engine had been stopped."