Buy OEM 1999 Porsche Part # PAB121809 (PAB-121-809). Engine Coolant Reservoir Cap Seal. 3.0 LITER, W/E-HYBRID. 4.0 LITER W/E-HYBRID. Engine Coolant Expansion Tank - Repair or Replace A

Engine Coolant Reservoir Cap Seal. Reservoir Cap gasket. Seal (tamper protect.
A circular disk covered in rubber or plastic with a hole in the center where the edge is sometimes tensioned by a spring that prevents fluid from leaking at the Engine Coolant Expansion Tank Cap.

Engine Coolant Reservoir Cap Seal

Fits Cayenne

3.0 LITER, W/E-HYBRID. 4.0 LITER W/E-HYBRID.
Engine Coolant Expansion Tank - Repair or Replace
A failed expansion tank can cause the cooling system in your 1999 Porsche to leak antifreeze, or it can cause your engine to overheat. If you're losing coolant, contact our service department to avoid engine damage.