OK. I just took my jeep (2008 4 door JK) to get a recall fixed and I was looking under the hood afterwords and I noticed there looked to be a cap missing. On the passenger side in the fron directly under the battery and air cleaner assembly, there is a tank with a hole on the top of it. It looks likere there should be a cap on it to stop dirt or mud from getting in, but honestly, I dont even know what that tank is for. I have attached a photo. If someone could please tell me if there jeep has a cap on this it would be most helpful. And Im obviously not a mechanic or someone who has spent much time working on cars, so if you could also tell me what that tank is it would also help. Much appreciated.