Sealent, Loctite 5926 Instant Gasket is a product you can use, it's resistant to high temperatures and engine fluids and remains flexiable. it says on the pack I have, and ok for oil sump pans.
Get it from an auto shop or Halfords
Have u tried nipping up the sump bolts first that's what I did. thats why i still have the pack of sealent.