Rails 4 ActionController::UrlGenerationError - ruby

Question

I'm getting this error ActionController::UrlGenerationError in Manufacturers#index along with No route matches {:action=>"new", :controller=>"cars"} missing required keys: [:manufacturer_id] for the following code. I have looked around and can't find the answer for this one.
cars_controller.rb
class CarsController < ApplicationController
def index
#cars = Car.all
end
def show
#car = Car.find(params[:id])
end
def new
#manufacturer = Manufacturer.find(params[:manufacturer_id])
#car = Car.new(params[:id])
#car.manufacturer = #manufacturer
end
def create
#manufacturer = Manufacturer.find(params[:manufacturer_id])
#car = Car.new(cars_params)
#car.manufacturer = #manufacturer
if #car.save
flash[:notice] = "You have successfully created a car"
redirect_to manufacturer_cars_path
else
render 'new'
end
end
private
def cars_params
params.require(:car).permit(:make, :color, :year, :mileage, :description, :country)
end
end
manufacturers_controller.rb
class ManufacturersController < ApplicationController
def index
#manufacturers = Manufacturer.all
end
def show
#manufacturer = Manufacturer.find(params[:id])
#car = Car.new
end
def new
#manufacturer = Manufacturer.new
end
def create
#manufacturer = Manufacturer.new(manufacturer_params)
if #manufacturer.save
flash[:notice] = "You have successfully created a new manufacturer"
redirect_to root_path(#manufacturer)
else
flash[:alert] = "Please try again"
render :new
end
end
private
def manufacturer_params
params.require(:manufacturer).permit(:name, :country)
end
end
models/car.rb
class Car < ActiveRecord::Base
belongs_to :manufacturer
validates :make, presence: true
validates :color, presence: true
validates :year, presence: true
validates :mileage, presence: true
validates :country, presence: true
end
models/manufacturer.rb
class Manufacturer < ActiveRecord::Base
has_many :cars
validates :name, presence: true
validates :country, presence: true
end
this link works in my cars/index.html.erb <%= link_to "Add Car", new_manufacturer_car_path %> but not in my layouts/application.html.erb or elsewhere. In manufacturers/index.html.erb it asks for the :manufacturer_id so i tried different ways and no luck. perhaps I'm missing something here.
these are my routes
Prefix Verb URI Pattern Controller#Action
root GET / manufacturers#index
manufacturer_cars GET /manufacturers/:manufacturer_id/cars(.:format) cars#index
POST /manufacturers/:manufacturer_id/cars(.:format) cars#create
new_manufacturer_car GET /manufacturers/:manufacturer_id/cars/new(.:format) cars#new
manufacturer_car GET /manufacturers/:manufacturer_id/cars/:id(.:format) cars#show
manufacturers GET /manufacturers(.:format) manufacturers#index
POST /manufacturers(.:format) manufacturers#create
new_manufacturer GET /manufacturers/new(.:format) manufacturers#new
manufacturer GET /manufacturers/:id(.:format) manufacturers#show
I appreciate the help.