Every 4 years (regardless of mileage)
1. The check must be performed when the engine is cool. Try to perform the check before the first engine start of the day.
2. Cover the lid with a cloth and slowly unscrew it.
3. Check the condition of the rubber seal on the lid. If it has hardened or cracked, the lid needs to be replaced.
4. If the car has been in use for several years or has a high mileage, it makes sense to replace the cap regardless of its condition. If the pressure relief valve built into the cap is faulty, then excessive pressure in the system can damage the hoses and other components of the cooling system.
(The article was taken in its entirety from the specified website FORDBOOK)