squeeky, chances are the magnets in the housing of the pump have come loose, they are normally glued into place but this glue often fails. Ask whoever you bought it from to take a look, and if it needs re-glued then it should be done with araldite, or a very strong epoxy resin.
as for the shurflo pumps we have been using them for years, the original pumps are still working fine, we bought new ones because we got a deal on them and felt it was a sensible option. Never had a problem with shurflo and highly recommend them - we use 4 pumps everyday and use a lot of water so they do get worked hard and have yet to fail us.
The first shurflo pumps we bought are now about 5years old and still going strong.