There is no "quick fix" they have to be replaced. You may find it easier to replace the solid metal ones with the bolt through rubber ones, but they require regular maintenance to make sure they stay tight and not leak.
Knock them out and put new ones in. The issue you may have is being able to reach them. I would NEVER use the rubber expandable type as they can leak over time when the rubber hardens due to exposure to heat from the engine.
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