When repairing holes bondo will not last. I am auto body tech by trade. If the
holes are small and under the gasket and you can't or don't choose to do it
right I would suggest (Oatey epoxy putty). In a pinch over a year ago I used
it to repair a hole in the steel cooling lines on my van and it's still
holding. Not saying this is the right way just a lot better than bondo. Dave