2001 kia sportage hubs

So i will be replacing some parts on this guys KIA i know. Well he said his 4wd is not working so i have to take a look at what it is and to fix it. I also was thinking the hubs to be a culprit the solenoid i already read about how to make it work if its closing or stuck open.

so if there the original would they leak. Or what else could cause 4wd not to work on a kia Sportage

Vacuum loss is the common problem, cause it relies on all the seals of front wheel, rather hard and expensive to test and to renew all of the components.
THe common solution is to go for auto- mechanical hubs, WARN type part number 61918. Here is some info about that:
www.avigex.ca/kia/hubinstall.pdf
Some restrictions in operation comes with that installation but with proper attention, they are extremely reliable. More on that subject when needed.
Some will prefer to opt for completely manual hubs, WARN type part number 60247, less expensive and fully predictable.