As the error states, associate accepts an eloquent model as first parameter, not a string. You need to pass it a colaborador model, not id.

Ok, nice information.

But what should I use to better accomplish my need? Is really instantiating an colaborador object? Or there is a simplest way?

Of course not, but since there is no disassociate method you need to set the FK value to null:

$veiculo->colaborador()->associate('NULL')->save();   

// change to:
$veiculo->colaborador_id = null;
$veiculo->save();

Obviously this will work only if you have set that column as nullable.

Hello, I tried that, the field is nullable. But its not setting the field to NULL.

Like this: $veiculo = Veiculo::find($id); $colid = $veiculo->colaborador_id;

                		$colaborador = Colaborador::find($colid);
			$colaborador->veiculo_id = null;
			$colaborador->save();
			$veiculo->colaborador_id = null;

And there is no change at that field.

You are setting a value on colaborador and trying to output a value on veiculo...