I bought coolant this morning as my car was running on empty. I was told to pour the whole 1 liter bottle in and top with water. After pouring the bottle of coolant in there's no room for water. What should I do?
My 2.5 litre engine has 7.5 liters of coolant. If the original mix is 50/50, and it goes down to 6.5 liters (3.25 liters of coolant + 3.25 liters of water), and you add 1 liter of coolant, you now have 4.25 liters of coolant and 3.25 liters of water. It's 57% coolant and 43% water. Not an ideal mixture, but if you keep doing that (add just coolant without water), the mixture will become richer and richer in coolant.
So, my advice would be to fix the coolant leak whenever convenient (being low on coolant is always as sign of a leak), and when it is fixed, fill it with proper mixture. You can in the mean time continue running on the 57/43 mix. No damage done by using this mixture, unless being low on coolant did some damage to your car.
If you have to add coolant again due to the leak being active, next time will with 1 liter of water only and then fill with 50% water, 50% coolant after that.
Of course, if you have some of those trendy 1 liter turbocharged little engines, they may have less coolant capacity and therefore your mixture could perhaps be so much off that it would be a good idea to repair the leak ASAP and fill with proper mixture.