A question about the coolant level in the coolant tank/ recovery bottle. Since the car is a 2000 s-type, it is kinda hard to see the level thru the side of it, noticed the shop that did the engine replacement filled it to almost the top, and have seen some drippage underneath around where the bottle is, checked the level this morning because it will be ac weather today in Chicago, around 90 and humid, and it needed about a red solo cup to fill the bottle to just under the neck where the cap fits. Wonder if it needs to be lower when car cold, and thats why there is some drippage after it is parked after being driven for 30 to 40 minutes. Rather there be too much than not enough and cook this motor, especially since it just came out of the shop getting the engine replaced. I noticed there's a couple posts of the coolant tanks leaking on the s-type so rather be safe.

 

When coolant is cold, the reservoir can be filled to the max line. And assuming you have no air pockets in your system, it should stay there. See a page like the following in your car’s Owners or Workshop manual:

 

2000 s-type boy, having the level "a red solo cup" below the neck to the cap is probably about where it should be. Yes, the coolant does expand some as the motor warms up and is probably the reason why you had a little bit of leakage when the car got warm (in short, you tried to take the coolant system "solid" which would result in major pressure changes with minimal temperature changes. The cap to the overflow bottle would have relieved the excess pressure/fluid, resulting in a "leak". I would say in the future, you can check the level by simply taking a q-tip and stick it in the cap opening and making sure that the fluid level is about 1.5-2 inches below the top of the overflow bottle (1/2 - 1 inch below where the bottle curves to form the sides). This will give you an easy way to check the level and not have to buy a new bottle. Granted, a new bottle would not be a bad idea.

 

The page from the S-Type Owner's Manual. Do note from the Workshop manual, there is sufficient room for heat expansion considered.