My 01 Bourbon (can ya tell I like to drink?) is really slow to heat up in the rear unit. My 99 was very similar. Is this common and more due to having to run the coolant through the length of the vehicle outside as well as the sheer volume of space it is trying to heat (BREATHE!) or could it be something else? The coolant levels are fine and fluid is normal color. Looks to have been serviced on a regular basis. Don't see any kinks in lines either.