The engine coolant expansion reservoir - a pressure-compensating overflow reservoir that collects excess coolant as the engine warms up and coolant expands, then returns coolant to the system as it cools down. It acts as a buffer to maintain correct coolant volume, system pressure, and prevent overflow or air ingress.
Fits:
Porsche 996 3.6L C2 / C4 / C4S 2001 - 2005
Porsche 996 Turbo 2001 - 2005
Porsche 996 GT2 2001 - 2005
Porsche 996 GT3 MKII / GT3 RS 2001 - 2005
Porsche 997.1 2005 - 2008 all models
Porsche 997.2 2009 - 2012 all models
This product supersedes Porsche's old part numbers:
- 99610615700, 99610615701, 99610615702, 99610615703, 99610615704
Over time, coolant expansion tanks are prone to degradation due to heat cycles, coolant chemical exposure, and pressure stress.
This can lead to:
• Cracks or stress fractures in the plastic tank body
• Leaks that cause coolant loss and risk of overheating or engine damage
• Loss of system pressure regulation, leading to air ingress, coolant boiling, or inefficient cooling
• Difficulty reading coolant level due to opaque or discolored plastic
Replacing the reservoir with a correctly-spec’ed tank ensures:
• Leak-free coolant containment under all operating conditions
• Proper coolant volume management through expansion and contraction cycles
• Stable cooling-system pressure and reliable thermal regulation
• Long-term reliability and prevention of coolant-related engine issues
You should replace the coolant expansion tank if you see cracks, coolant leaks, or coolant residue around or under the tank, especially after long periods of heat. If the plastic has become brittle, discoloured, or feels soft/warped, or if coolant level fluctuate without obvious cause — the tank may no longer maintain pressure or hold coolant reliably, and replacement is warranted.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610615704
The product you are viewing cross references to these numbers
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
- Porsche 996 TURBO 2000-05
- Porsche 996 GT2 2001-05
- Porsche 996 GT3 MKII 2003>>
- Porsche 996 GT3 RS 2003-04
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
- Porsche 997 MK1 TURBO 2007-09
- Porsche 997 MK1 GT3 2007-09
- Porsche 997 MK1 GT2 2007-09
- Porsche 997 MKII Carrera C2 3.6L 2009-12
- Porsche 997 MKII Carrera C4 3.6L 2009-12
- Porsche 997 MKII Carrera C2S 3.8L 2009-12
- Porsche 997 MKII Carrera C4S 3.8L 2009-12
- Porsche 997 MKII GT3 2010-11
- Porsche 997 MKII Turbo 2010-13
