While I am not familiar of any barriers about the equator in any of the books I read about the Portuguese exploration (there is actually very little sources about the crossing the equator itself )

But for sure there had been such a barrier at the beginning of the exploration of Africa in Cape Bojador. According to chronicler Azurara or Zurara, this Cape was for several generations considered impassable. Description Zurara provides did not contain any monster but simply put that the land was deserted and literally a desert, barren with no water, plants, animals or people. And that the sea was shallow and currents too strong.

It seems the Infante Henrique (Prince Henry the Navigator) was attempting for several years to convince his captains to sail beyond it before one Gil Eanes finally did it in 1434 (also on his second trip as on his first he decided not to even attempt it out of fear) He then found the land and sea beyond the Cape quite different then expected, actually quite navigable and more or less the same as the land before. This encouraged the portuguese and soon more expeditions went beyond and the exploration of West Africa began

Sources:

The Chronicle of the Discovery and Conquest of Guinea. Vol. I by Zurara (Chapter VIII)
A History of Portugal and the Portuguese Empire: From Beginnings to 1807 (Volume 2), A. R. Disney