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- Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
- Porsche 911 1978-1983 3.0L / SC
- Porsche 911 1984-1986 3.2L
- Porsche 911 1987-1989 3.2L G50
- Porsche 911 1975-1977 3.0L Turbo (930)
- Porsche 911 1978-1989 3.3L Turbo (930)
- 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 914 (1970-1976)
This locking nut is critical in maintaining the correct clearance setting between the rocker-arm or cam follower and valve stem, ensuring reliable valvetrain performance and correct engine behavior.
SET OF 12
Fits:
Porsche 911 1973 - 1989
Porsche 911 Turbo 1975 - 1989
Porsche 964 C2 / C4 / RS 1989 - 1994
Porsche 964 Turbo 1991 - 1994
Porsche 914 1970 - 1976
Porsche 914/6 1970 - 1972
Diagram ref no 50
• Position on Vehicle: Engine cylinder head, at the valve adjusting screw area - used to lock the adjuster once clearance is set.
• Function: Locks the valve-adjusting screw in place, ensures the correct clearance remains unchanged under engine operation, prevents loosening of adjuster and ensures valvetrain reliability.
• Specification: M8 × 1 thread, correct height and socket size, treated or coated for durability - direct-fit replacement of Porsche part number 99903400500.
• Applications: Ideal when your original nut is damaged, the adjuster is loose, you are doing a valve-clearance service, or you require reliable hardware for engine rebuilds.
While small, this locking nut performs a vital role: without it, the adjuster can drift, valve clearance can open up or close down, leading to noisy operation, performance loss, premature wear or even engine damage. Symptoms of a failing/incorrect nut include adjusting screw backing out, noisy valvetrain, incorrect clearance and poor idle or performance.
When to replace:
• The adjuster locking nut is missing, corroded, rounded or damaged.
• After valve-clearance adjustment and you want guaranteed lock-in of the setting.
• During engine rebuild or cylinder-head service when valvetrain hardware is exposed.
• To replace the original with fresh hardware to maintain service integrity and reliability.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99903400500
The product you are viewing cross references to these numbers
This kit is comprised of the following items:
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche Boxster 987 2.7L 2005-08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
- Porsche Boxster 987 MKII 2.9L 2009-12
- Porsche Boxster S 987 MKII 3.4L 2009-12
- Porsche Boxster 981 2.7L 2012-16
- Porsche Boxster 981 S / GTS 3.4L 2012-16
- Porsche Boxster 981 Spyder 3.8L 2016
- 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 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- 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 MKI 1999-02
- 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 / GT3 RS 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 / GT3 RS 2010-11
- Porsche 997 MKII Turbo 2010-13
- Porsche 997 MKII GT2 RS 2011-13
- Porsche 911 (997) GT3 CUP 2010
- Porsche 991.1 Carrera C2 3.4L (350 Bhp) 2012-16
- Porsche 991.1 Carrera C2S / GTS 3.8L (400/430 Bhp) 2012-16
- Porsche 991.1 Carrera C4 3.4L (350 Bhp) 2012-16
- Porsche 991.1 Carrera C4S / GTS 3.8L (400/430 Bhp) 2012-16
- Porsche 991.1 Turbo 3.8L (520 Bhp) 2014-16
- Porsche 991.1 Turbo S 3.8L (560 Bhp) 2014-16
- Porsche 991.2 Carrera 2 3.0L (370 Bhp) 2016-19
- Porsche 991.2 Carrera 2S / GTS 3.0L (420/450 Bhp) 2016-19
- Porsche 991.2 Carrera 4 3.0L (370 Bhp) 2016-19
- Porsche 991.2 Carrera 4S / GTS 3.0L (420/450 Bhp) 2016-19
- Porsche 991.2 Cabriolet 2 3.0L (370 Bhp) 2016-19
- Porsche 991.2 Cabriolet 2S / GTS 3.0L (420/450 Bhp) 2016-19
- Porsche 991.2 Cabriolet 4 3.0L (370 Bhp) 2016-19
- Porsche 991.2 Cabriolet 4S / GTS 3.0L (420/450 Bhp) 2016-19
- Porsche 991.2 Targa 4 3.0L (370 Bhp) 2016-19
- Porsche 991.2 Targa 4S / GTS 3.0L (420/450 Bhp) 2016-19
- Porsche Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
- Porsche Cayman 2.9L 987C MKII 2009-12
- Porsche Cayman S / R 3.4L 987C MKII 2009-12
- Porsche Cayman 2.7L 981 2013-16
- Porsche Cayman S / GTS 3.4L 981 2013-16
- Porsche Cayman GT4 3.8L 2015-16
- Porsche 955 Cayenne 3.2L V6 2003-06
- Porsche 955 Cayenne S 4.5L V8 2003-06
- Porsche 955 Cayenne Turbo 4.5L 2003-06
- Porsche 955 Cayenne Turbo S 4.5L 2006>>
- Porsche 957 Cayenne 3.0L Diesel 2007-10
- Porsche 957 Cayenne 3.6L 2007-10
- Porsche 957 Cayenne S / GTS 4.8L 2007-10
- Porsche 957 Cayenne Turbo / Turbo S 4.8L 2007-10
- Porsche 958 Cayenne V6 3.6L Petrol (300Hp) 2010-17
- Porsche 958 Cayenne V6 3.0L Diesel (245Hp) 2010-17
- Porsche 958 Cayenne S V6 3.0L Hybrid (380Hp) 2010-17
- Porsche 958 Cayenne S V8 4.8L Petrol (400Hp) 2010-17
- Porsche 958 Cayenne S V8 4.2L Diesel (382Hp) 2010-17
- Porsche 958 Cayenne GTS V8 4.8L Petrol (400Hp) 2010-17
- Porsche 958 Cayenne Turbo V8 4.8L Petrol (500Hp) 2010-17
- Porsche 958 Cayenne Turbo S V8 4.8L Petrol (550Hp) 2010-17
- Porsche 95B.1 Macan Petrol 2.0L (237Bhp) 2014-18
- Porsche 95B.1 Macan S Petrol 3.0L V6 (340Bhp) 2014-18
- Porsche 95B.1 Macan S Diesel 3.0L V6 (258Bhp) 2014-18
- Porsche 95B.1 Macan GTS Petrol 3.0L V6 (360Bhp) 2014-18
- Porsche 95B.1 Macan Turbo 3.6L V6 (400Bhp) 2014-18
- Porsche 924S 2.5L 1986-87
- Porsche 924S 2.5L 1988
- Porsche 944 2.5L 8V 1982-87
- Porsche 944 2.7L 8V 1988-89
- Porsche 944S 2.5L 16V 1987-88
- Porsche 944S2 3.0L 16V 1989-91
- Porsche 944 Turbo 2.5L 8V 1985-88
- Porsche 944 Turbo 2.5L 8V 1989-91
- Porsche 944 Turbo S 2.5L 8V 1988
- Porsche 968 3.0L 1992-94
- Porsche 968 Sport 3.0L 1994-95
- Porsche 968 CS 3.0L 1993-95
- Porsche 968 Turbo S 3.0L 1993-94
- 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
LIQUI MOLY Hydraulic Lifter Additive – 300ml
LIQUI MOLY Hydraulic Lifter Additive is an engine oil treatment designed to reduce noisy hydraulic tappets and improve the operation of oil-fed valve train components.
Its cleaning formula helps remove deposits from oil passages and valve bores, supporting smoother engine operation and improving the function of oil-pressure-operated timing chain tensioners.
What Does It Do?
The additive cleans oil passages and valve bores, helping hydraulic lifters operate correctly. It may also reduce noise from oil-pressure-operated timing chain tensioners.
Why Do Hydraulic Lifters Become Noisy?
Common causes include:
- Deposits restricting oil passages
- Contaminated or ageing engine oil
- Poor lubrication during cold starts
- Low engine oil pressure
- Internal lifter wear
When Should It Be Used?
Use when hydraulic tappet noise may be caused by deposits or restricted oil flow.
It can be added during routine servicing. Persistent mechanical noise requires diagnosis, as additives cannot repair worn or damaged components.
Application & Dosage
- Add directly to the engine oil.
- One 300ml container treats up to 6 litres of oil.
- Adjust the dosage proportionally for larger oil capacities.
- Can be added at any time.
- Warm the engine after adding.
- LIQUI MOLY recommends use after each oil change for a lasting effect.
Key Features
- Helps reduce hydraulic tappet noise
- Cleans oil passages and valve bores
- Improves engine oil lubrication properties
- Supports oil-pressure-operated timing chain tensioners
- Suitable for compatible petrol and diesel engines
- Tested for turbochargers and catalytic converters
- Suitable for engines with diesel particulate filters
- Compatible with commercially available engine oils
- 300ml container
LIQUI MOLY Hydraulic Lifter Additives for Porsche Engines
Hydraulic lifters rely on clean engine oil and unrestricted oil passages for reliable operation.
LIQUI MOLY Hydraulic Lifter Additive helps remove deposits that can contribute to noisy tappets and restricted lubrication in compatible Porsche petrol and diesel engines.
Design911 supplies LIQUI MOLY engine additives, lubricants, oil filters and Porsche maintenance products.