First, If you added less than 1/2 bottle to the expansion tank, it should not be an issue. However, there is a reason this liquid needs to be thinned with water. It is not designed to be used at full strength. It is generally too thick and over time will damage the water pump as the pump will need to work harder to push the coolant in the system. Additionally, there needs to be a balance between freeze/boil over protection so it also needs to be diluted for that reason as well.
The second question you asked is about removing some of the coolant that you added. Yes, it is possible to do this by using a siphon (buy at most auto stores for just a few dollars). However, I do not recommend this. In my opinion, if you are truly concerned that you have added too much incorrect coolant then you need to drain the system. A very quick fix to this situation can be to disconnect the lower radiator hose to quickly drain the radiator. reconnect the hose and refill the radiator with the proper percentages of coolant. (many newer products already come prediluted so these mistakes do not happen).
There are a few other things to mention: Your car holds roughly 12 quarts of coolant; you stated you added approx 1/2 gallon (2 quarts); keeping this in mind on an overall ratio there should be no cause for alarm and you can leave well enough alone. Also, why are you adding coolant? Unless there is a leak in the system, generally you should not need to add any coolant. If you have not already done so check the system for leaks.
I hope this is of some help to you
The reason that you aren't supposed to add full strength coolant is (believe it or not) full strength coolant will freeze faster than water mix. If the coolant mix in the car was EXTREMELY cold, the added coolant could freeze, clogging the system. Rather than explaining all of this, the manufacturers just tell you not to do it.
Just the expansion tank & not the radiator ?? If it was JUST the smaller tank, it wouldn't hurt anything. The coolant goes in & out of that tank as the engine heats & cools, so it will be mixed with the rest of the engine coolant very quickly.
Yes, just the expansion tank and it wasn't the entire bottle. Maybe a little less than half.
It will be fine, a lot better than just pure water.
wont do any harm ..in time it will circulate and dilute at same time ...but its great for finding leaks in cooling system
i fit was just a small amount to add to the tank no need to worry....
I accidentally poured the full strength coolant in the reservoir without diluting it first, will this mess up my car? Can pull some of it out some kind of way and add water? It's a 2006 Mercedes C230.
