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Oil Thermostat

Fits:
Porsche 993 1994-97
Click 'Zoom in' for large parts diagram.
Diagram Ref No 3.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99320725802
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
For drain plug on thermostat housing.
The Porsche Genuine OE Oil Drain Plug O-Ring (Part No. 99970126940) is a factory-specified sealing ring designed for the engine oil drain plug on Porsche 993 models. This small but essential component forms a tight seal between the drain plug and the engine oil sump or tank, preventing oil leakage during operation and after routine oil changes.
Fits:
Porsche 993 1994 - 1997
Diagram Ref No 6
The oil drain plug O-ring sits around the drain plug sealing surface and compresses slightly when the plug is tightened. This compression creates a leak-proof seal that prevents engine oil from escaping around the plug threads.
By maintaining proper sealing, the O-ring helps ensure the engine lubrication system remains closed and secure, preventing oil loss and protecting surrounding components from contamination.
Fitment / Position on Car
• Fitting position: Engine oil drain plug
• Location: Between the drain plug and sump or oil tank sealing surface
• System: Engine lubrication / oil service system
Functions & Technical Role
• Leak prevention: Forms a tight seal around the oil drain plug
• Compression sealing: Flexible rubber O-ring compresses when tightened to prevent leaks
• Oil resistance: Designed to withstand continuous contact with hot engine oil
• Service component: Recommended replacement during oil changes
• OEM specification: Porsche-engineered dimensions ensure correct fit and reliable sealing
O-rings are designed to compress once to create a proper seal. Over time they can harden, flatten, or degrade due to heat and oil exposure, increasing the risk of leaks. Replacing the O-ring during oil service helps maintain a clean, leak-free engine oil system and protects surrounding components from oil contamination.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99970126940
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
This OE Match oil drain plug O-ring is a small sealing gasket designed for the oil drain plug on the oil thermostat housing in Porsche 911 (993) models. It provides a tight seal between the drain plug and the housing to prevent engine oil leaks during operation and after servicing.
Sold each
Fits:
Porsche 993 1994 - 1997
Diagram Ref No 6.
The oil drain plug O-ring is a rubber sealing ring installed on the oil drain plug located on the oil thermostat console or housing. Its function is to create a tight seal when the drain plug is tightened, preventing oil leakage from the engine lubrication system.
The OE Match version of part number 99970126940 is produced with the correct 11 × 2.5 mm dimensions, matching the original Porsche specification. This ensures proper compression and sealing performance when the drain plug is installed.
Because this component is removed whenever oil is drained from the thermostat housing, it is considered a service item and is commonly replaced during routine maintenance.
The O-ring seals the interface between the oil drain plug and the thermostat housing, preventing engine oil from leaking out of the lubrication system. It maintains proper oil pressure and protects the engine from oil loss.
Replacing the seal during servicing ensures the drain plug forms a secure seal and helps prevent oil seepage after maintenance.
Function
• Leak Prevention: Seals the oil drain plug on the thermostat housing
• Oil System Integrity: Maintains proper oil containment and pressure
• Service Seal: Designed to be replaced during oil system maintenance
• Engine Protection: Helps prevent oil loss and contamination
O-rings are exposed to heat, oil and repeated tightening cycles. Over time the rubber can harden, flatten or crack, which may lead to oil seepage or leaks around the drain plug. Replacing the O-ring whenever the plug is removed ensures the lubrication system remains properly sealed and helps prevent oil loss.
Consider replacing the O-ring when:
• Performing engine oil service
• Removing the oil thermostat housing drain plug
• The seal appears flattened, cracked or hardened
• Oil leakage is visible around the drain plug
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99970126940
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97

Fits:
Porsche 924 Turbo/GT
Porsche 928 1978-95
Porsche 993 1994-97
Click pictrue for large parts diagram.
Diagram Ref No 11.
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
- Porsche 924 Turbo 2.0L 1979-81
- Porsche 924 Turbo 2.0L 1982-84
- Porsche 924 Carrera GT 2.0L 1981
- Porsche 924 Carrera GTS 2.0L 1982
- Porsche 928 4.5L 1978-82
- Porsche 928S 4.7L 1981-83
- Porsche 928S2 4.7L 1984-86
- Porsche 928S4 5.0L 1987-92
- Porsche 928GT 5.0L 1989-91
- Porsche 928GTS 5.4L 1992-95

Fits:
Porsche 924 1976-85
Porsche 928 1978-95
Porsche 993 1994-97
Click pictrue for large parts diagram.
Diagram Ref No 12.
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
- Porsche 924 2.0L 1976-79
- Porsche 924 2.0L 1980-85
- Porsche 924 Turbo 2.0L 1979-81
- Porsche 924 Turbo 2.0L 1982-84
- Porsche 924 Carrera GT 2.0L 1981
- Porsche 924 Carrera GTS 2.0L 1982
- Porsche 928 4.5L 1978-82
- Porsche 928S 4.7L 1981-83
- Porsche 928S2 4.7L 1984-86
- Porsche 928S4 5.0L 1987-92
- Porsche 928GT 5.0L 1989-91
- Porsche 928GTS 5.4L 1992-95
Fits:
Porsche 993 1994-97
Click 'Zoom in' for large parts diagram.
Diagram Ref No 7.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99904111100
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97

Fits:
Porsche 924 Turbo/GT
Porsche 928 1978-95
Porsche 993 1994-97
Click pictrue for large parts diagram.
Diagram Ref No 10.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
92810717202
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
- Porsche 924 Turbo 2.0L 1979-81
- Porsche 924 Turbo 2.0L 1982-84
- Porsche 924 Carrera GT 2.0L 1981
- Porsche 924 Carrera GTS 2.0L 1982
- Porsche 928 4.5L 1978-82
- Porsche 928S 4.7L 1981-83
- Porsche 928S2 4.7L 1984-86
- Porsche 928S4 5.0L 1987-92
- Porsche 928GT 5.0L 1989-91
- Porsche 928GTS 5.4L 1992-95

Fits:
Porsche 964 1990-94
Porsche 993 1994-97
Click picture for large parts diagram.
Diagram Ref No 9.
- Porsche 964 (911) C2 1989-93
- Porsche 964 (911) C4 1989-93
- Porsche 964 (911) RS 3.6L 1991-93
- Porsche 964 (911) RS 3.8L 1991-93
- Porsche 964 (911) TURBO 3.3L 1991-93
- Porsche 964 (911) TURBO 3.6L 1991-93
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97

Fits:
Porsche 993 1994-97
Click 'Zoom in' for large parts diagram.
Diagram Ref No 8.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99320735101
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97

Fits:
Porsche 993 1994-97
Click 'Zoom in' for large parts diagram.
Diagram Ref No 8.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99320735101
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97

Fits:
Porsche 993 1994-97
Click 'Zoom in' for large parts diagram.
Diagram Ref No 1.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99320705803
The product you are viewing cross references to these numbers
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
Oil Thermostats – Precision Temperature Regulation for Porsche Engines
The oil thermostat plays a vital role in your Porsche’s lubrication and cooling system by controlling oil flow based on temperature. It ensures that your engine oil warms up quickly to the ideal operating temperature and maintains stability during demanding driving conditions. This optimised oil temperature improves performance, efficiency, and long-term engine protection.
At Design911, we supply a range of oil thermostats and related components designed for reliability and accuracy across both classic and modern Porsche models. Manufactured using high-quality heat-resistant alloys and durable seals, our thermostats guarantee smooth operation, consistent flow control, and a perfect fit for your Porsche’s lubrication system.
Whether you’re maintaining a 911, Cayman, or Panamera, our oil thermostats deliver the precise temperature regulation your engine demands for both everyday use and performance driving.
What Do Oil Thermostats Do?
An oil thermostat regulates when oil is diverted through the oil cooler, based on temperature readings.
Core Functions:
- Control
oil flow between the engine and the oil cooler.
- Ensure
rapid oil warm-up to reduce cold-start wear.
- Maintain
stable operating temperatures during all conditions.
- Protect
against overheating under high loads.
- Support optimal lubrication and efficiency.
By keeping oil within the correct temperature range, the thermostat helps your Porsche achieve consistent performance, better fuel economy, and extended engine life.
Why Do Oil Thermostats Fail?
Over time, continuous exposure to high temperatures, oil contamination, and mechanical wear can cause oil thermostats to degrade or malfunction.
Common Causes of Failure Include:
- Sticking
or seized valves due to sludge or varnish build-up.
- Thermal
fatigue from repeated heating and cooling cycles.
- Cracked
housings or worn seals, leading to leaks.
- Oil
contamination affecting thermal response.
- Improper temperature regulation, causing overheating or slow warm-up.
Signs of a failing thermostat include oil temperature
fluctuations, overheating, or delayed oil circulation, which can result in
reduced engine protection and performance.
Why Replace Oil Thermostat Components?
A faulty thermostat can cause erratic oil flow, engine wear, or overheating. Replacing it with a high-quality, precision-engineered unit ensures reliable temperature control, smoother oil circulation, and consistent lubrication.
Key Benefits:
- Restores accurate oil temperature regulation.
- Prevents overheating and cold-start damage.
- Improves oil flow and engine efficiency.
- Built from heat- and corrosion-resistant materials.
- Direct-fit
compatibility with a wide range of Porsche models.
- Ideal for servicing, engine rebuilds, or performance upgrades.
Replacing an ageing thermostat is an essential part of maintaining your Porsche’s lubrication system and preventing premature engine wear.
Highlights:
- Precision-engineered Porsche oil thermostats for reliable control.
- Ensures optimal oil flow and temperature regulation.
- Constructed from premium heat-resistant materials.
- Direct-fit design for 911, Cayman, Boxster, Panamera and more.
- Ideal for routine maintenance or high-performance applications.
- Maintains peak engine performance and longevity.