He found + present/past tense
I don't really think it has so much to do with the grammar of the simple present tense (i.e. used for permanent actions, general truths etc) as the speaker's choice at the time of speaking. Based on the speaker's perspective, both the simple present and the simple past tenses would be possible.
As I see it, the speaker would equally produce either
- "I found (that) Sam's room was closed"
referring to the time he went there and saw it was closed as implied by the use of the simple past tense in the verb and regardless of whether or not it is still closed or
- "I found (that) Sam's room is closed"
referring to the fact that it is closed at the time of speaking.
In other words, I don't think it should be a matter of what is (or sounds) correct, but a matter of intended meaning and/or chosen time reference.
However, bear in mind that were the speaker reporting the fact at a later time, the simple past tense would be in accordance with the Indirect (or Reported) Speech despite the fact that not all speakers adhere to its rules in cases where it makes little or no difference.
I have been requested to weigh in on this question, because of a similar question posed by the poster. Maybe the forest of comments came to the same conclusion. I apologize for not having waded through them yet.
A says to B : "You go to Sam's room and see if Sam's sleeping."
B : "Okay" B leaves and find that Sam's room is closed. 5 minutes later B returns and tells A about Sam room.
A: Did you go there ?
B: Yes I went there and I found that Sam's room is closed.
I'm going to rewrite this slightly, to make it more representative of family life in my house. That makes it easier for me to imagine the dialogue vividly. (As written, this dialogue is perfectly understandable, though.)
A: (to B) Go see if Sam's sleeping, please. (I, the mother, am probably A; my younger son is B, and my teenaged son, prize-winning sleeper, is Sam.)
B : Okay. Leaves.... Returns after a moment. His door is shut and I can't hear anything.
On the other hand, I can perfectly well imagine that my younger son might get distracted and start playing with the cat on the way back to the kitchen. Then it might go like this:
A: (to B) Go see if Sam's sleeping, please.
B : Okay. Leaves. Wanders back into the kitchen five minutes later.
A: What happened? What's Sam doing?
B: I'm not sure. I think maybe he's asleep. His door was shut and I couldn't hear anything.
However, even in this case, B might say, "His door is shut and I can't hear anything."
Being a former English as a Second Language teacher, and my family being trilingual, I am infamous for my nitpicking over tenses. But even I would find nothing wrong with the present tense version being given with a five minutes delay.
What I'm saying is that it doesn't really matter whether you use the present or the past in a situation like this.