Here's why:
* Improper Seating: The old seal may be damaged or stuck, preventing the new seal from seating properly. Removing the sleeve ensures a clean, even surface for the new seal.
* Damage to the Seal: Forcing a new seal in over an old, potentially damaged sleeve risks damaging the new seal's lip, leading to premature failure.
* Wear and Tear: The sleeve itself might be worn or damaged, contributing to the original seal failure. Replacing it ensures a better seal.
* Compatibility: Some aftermarket seals may require a specific fitment or clearance, which removing the sleeve can help achieve.
However, there are caveats:
* Some designs don't require it: While less common, some engine designs might not necessitate sleeve removal. Consult a repair manual specific to your year and model Mustang V6 engine. The manual will be your definitive guide.
* Potential for Damage: Removing the sleeve requires care to avoid damaging the crankshaft or the engine block. If you're uncomfortable doing this, consider having a professional mechanic perform the repair.
In summary: While not always absolutely necessary, removing the sleeve is the safer and more reliable approach when replacing a front crankshaft seal, especially an aftermarket one. Always consult your repair manual for specific instructions and recommendations for your vehicle.
