Rinse and drain the sauerkraut and place in the bottom of crockpot. Mix the brown sugar, caraway seeds, salt and pepper (to taste) with the sauerkraut. Place onion slices on top.
Heat oil over med-high heat in a large skillet or Dutch oven. Season pork with the garlic and salt and pepper. Brown pork lightly on all sides and remove from skillet. Place meat on top of sauerkraut and onions.
Pour one can of beer over the pork and sauerkraut. Sprinkle the thyme leaves over pork.
Cover and cook on low for 8 hours. About two hours before the pork will be done, add the kielbasa pieces around the pork in the crockpot. Give them a little push down into the juices.
If your pork loin roast is smaller than the one I used, the cook time may not take 8 hours. Check it periodically, internal temperature should be at least 160 degrees. My pork was falling apart when it was done. I also turned the roast over a couple of times, totally not necessary though.
Serve with mashed potatoes to complete the traditional meal.