Q: Did the Hogwarts' Express take a detour in Prisoner of Azkaban? Did the Hogwarts' Express take a detour in Harry Potter and the Prisoner of Azkaban to pick up the Dementors?
Yesterday, I listened to the German audio book and there Ron complains that it takes pretty long to arrive at Hogwarts.
When the train stops to pick up the Dementors, the three think that they actually are at Hogwarts, so the time to get to the pick up place is roughly the same as the time to get to Hogwarts.
It could also be, that the train had to go slower because there was some heavy raining going on.
Is there any source gives some explanation about this passage?

The rain thickened as the train sped yet farther north; the windows were now a solid, shimmering gray, which graduily darkened until lanterns flickered into life all along the corridors and over the luggage racks. The train rattled, the rain hammered, the ind roared, but still, Professor Lupin slept.
"We must be nearly there," said Ron, leaning forward to look past Professor Lupin at the now completely black window.
The words had hardly left him when the train started to slow down.
  "Great," said Ron, getting up and walking carefully past Professor Lupin
  to try and see outside. "I'm starving. I want to get to the feast…"
Prisoner of Azkaban, chapter 5 (The Dementor)


A: No.
They weren't picking up the Dementors en route to Hogwarts; they met the Dementors at the castle boundary, and the Dementors searched the train. Dumbledore explains this at the start-of-term feast:

Dumbledore cleared his throat and continued, "As you will all be aware after their search of the Hogwarts Express, our school is presently playing host to some of the dementors of Azkaban, who are here on Ministry of Magic business."

I'd add that the nature of the stop isn't consistent with a planned detour. A few notes:


*

*The stop doesn't seem to be planned. The train slows down somewhat before it stops, but this is the final stop:

The train came to a stop with a jolt, and distant thuds and bangs told them that luggage had fallen out of the racks. Then, without warning, all the lamps went out and they were plunged into total darkness.

If the driver knew they were coming to a stop along a prearranged detour, then I'd think the stop would be a bit more graceful.

*They stop before they should have reached Hogwarts. Although Ron has convinced himself that they're at Hogwarts, I'm more inclined to trust Hermione on this one:

"We can't be there yet," said Hermione, checking her watch.

