So for the 4th time this year my warning light came on, upon inspection the level in the small reserve tank was low, I have refilled it to max line each time which is not much, there is no apparent leak as I park in the same place at work every day. My question is, where is my coolant disappearing to, is there a common problem that occurs with this model and engine, something that is on it's way out but not at catastrophic failure time yet. What should I look at to narrow down the possible parts within the cooling system. Ideas people. Mike.

 

What year and engine do you have?

 

Could be the heater core. The floor can soak up quite a bit of coolant before you realize it.

 

Is it the '08 XC90 ?? About how much time from from topping it off to the next ??
If you have a very small leak it might be in a place where the coolant is boiling off from contact with the hot engine so nothing makes it to the ground. It could be a hose end or even the start of a head gasket failure. Or like above, someplace you can't see like the heater core or it's connections or on the back of the engine.
Going over it visually would be a start and from there if nothing is found you can add a dye that fluoresces under black light to find difficult leaks. But for that you need a black light bulb and some yellow glasses. Or go to an auto parts store and get their loaner kit for pressurizing the system. Or do both the dye and pressure.

 

Kiss4afrog. Yes it is the 08 XC90, it did this once last year, I live in north Louisiana so it's hot and I can live with that, but 4 times this year since the start of summer, I can not live with that, not sure how big the reserve tank is but I would guess that I add no more than 1/2 a qt. I'll give the engine bay a wash and go from there, visual inspection and move on to a pressure test than on to the dye test. Still, I am just curious as to if there is a common failure with this engine and or model, my wife drives a Bimmer and I'm well versed in the cooling system and what are the common problems.