I have a '78 124 that I have been restoring. I have not started it up for a few weeks. This morning I started it up and heard a gurgling noise coming from the crankcase breather hose that connects to the air filter housing. I let the car run for a few minutes but the noise continued. I put my finger over the end of the hose and the sound was muffled, letting my know it was comming from the hose. I know that hose connects to a breather unit on the side of the engine, which in turn has a tube leading into the oil pan area. I changed my oil a while back and rechecked the level and it was up to the correct level. I am getting oil up to the top of the engine but what can be causing the gurgling noise?