Singer 5040c i just bought this machine it was working fine but i thought i should clean it after cleaning all of a sudden the bottom thread is looping up all over and the tension is not right. When I adjust the tension knob, nothing happens! Help, why is the bottom thread all messed up? I made sure I threaded it correctly,i cleaned down part too remove down belt too,after that these thinghs happened.pls help me out for this.

Have you taken out the bobbin plate where the screws are and clean inside. I have had the same problem and cleaned out all the thread and it worked fine.

Clean the machine and oil where the manufacturer instructs you to do so. Inspect your bobbin case for bits of thread and lint. re-thread machine and wind a new bobbin. Make sure you're using a good needle, that it isn't bent, dull, or burred. Be sure you're using the correct needle for the type of fabric you're sewing. If you're still having issues, adjust your tensions, both top and bobbin tensions must match to make a proper stitch. adjusting the bobbin tension should be done in very small increments and then tested.

first ,re thread the upper bobbin, check the needle to match the fabric and the lower bobbin thread should be the same like the upper thread. If it dose not work, clean the discs tension for the upper thread.

when the needle breaks on a pin that can cause a
problem with the timing, the machine needs to be serviced

Look for screws and snap in tab locations like getting into a laptop or an xbox. you'll need some sort of stiff thin tool to do this. Good luck

Your machine needs a professional to fix your timing and tune it up. You may have messed up the timing when you took off the belt. It is worth getting it fixed.

You can get a users manual from the Singer Website for model 5040.

Thread the machine with the presser foot up and see if this helps.

Is your bobbin clean and inserted correctly? (counter clockwise) A little fuzz can be a problem. Clean with a q-tip and oil if needed.

We have those bobbins available here:

Singer Sewing Machine Bobbins

I have the same problem. Driving me nuts. The tension dial is broken, as far as I can tell. Just craps out from time to time. Sometimes turning it on and off helps. I personally think it's a problem with the electronic controls.