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Porsche · Known Issues

2004 Porsche 911 Problems: 3 Known Issues

2004 model year · 12,100+ owner reports · Updated September 2026

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Issue summary

According to Au7o's analysis of 12,100+ owner reports, the 2004 Porsche 911 has 3 documented known issues, with 1 rated critical. The most serious is Intermediate Shaft (IMS) Bearing Failure ($2,000-$4,500 repair). The most commonly reported issue is Intermediate Shaft (IMS) Bearing Failure with 5,500 owner reports. Across all issues with published estimates, repair costs range from $500 to $4,500. DIY maintenance guides at au7o.io.

In This Article

  • 911 Engine3
  • Recalls7
  • FAQ
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In This Article

  • Engine3
  • Recalls7
  • FAQ

All 3 Known Issues

Filter:
ALL YEARS202620252024202320222021202020192018201720162015201420132012201120102009200820072006200520042003200220012000199919891986198319821980197819761975197419731972197019681965

When Issues Typically Appear

Intermediate Shaft (IMS) Bearing Failure
40K-120K
Rear Main Seal (RMS) Oil Leak
50K-120K
Air-Oil Separator (AOS) Failure
50K-100K
038K75K113K150K mi
Community reported
5,500 owners

On the 1999-2008 Porsche 911, the IMS bearing on 996 and early 997 flat-six engines is a single-row or dual-row sealed bearing that loses lubrication over time, leading to catastrophic bearing failure and engine destruction. The dual-row bearing (1999-2005) fails less frequently than the single-row (2006-2008), but both are a major concern. This is the most feared and well-documented Porsche defect of the modern era.

This issue also affects: Audi R8, Porsche Boxster, Porsche Cayman

Common Symptoms

  • Metallic debris in oil filter at oil change
  • Rumbling or grinding noise from rear of engine
  • Sudden catastrophic engine seizure
  • Oil analysis showing elevated copper and lead
  • Check engine light with oil pressure codes

How to Fix

Replace the IMS bearing with an upgraded ceramic hybrid bearing (LN Engineering IMS Solution or IMS Retrofit). This can be done with the engine in the car during a clutch replacement. On 2006-2008 single-row cars, replacement is strongly recommended as a preventive measure.

What you need to fix it

Only diagnosis- and fitment-reviewed repair parts are linked here.

  • LN Engineering 106-08.40 dual-row IMS Solution kit

    1999 Porsche 996 911 and confirmed dual-row 2000-2001 M96 engines; SKU 106-08.40. Identify the actual bearing/engine first, prequalify it and use a qualified Porsche specialist.

    LN Engineering
  • LN Engineering 106-08.20 single-row IMS Solution kit

    Confirmed single-row 2000-2005 Porsche 996/early 997 M96 or early M97 engines, SKU 106-08.20. Excludes late non-serviceable 2005 engines and all 2006-2008 large-bearing engines unless the engine is completely disassembled.

    LN Engineering

As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.

Owner tips & cautions

  • WarningCut open the oil filter at every oil change and inspect for metallic debris — this is the earliest warning sign of IMS bearing deterioration.
Typical repair cost:$2,000 - $4,500

Research This Issue

Based on 5,500 owner reports

GoogleRedditYouTubeNHTSA
Community Reported
High Confidence5,500 owner reportsLast reported by owners Jan 2026Reviewed Mar 2026
Community reported
3,800 owners

On the 1999-2019 Porsche 911, the rear main seal on the M96, M97, and MA1 flat-six engines is prone to leaking oil onto the clutch and flywheel. The seal hardens over time and the flange design allows oil to migrate past the seal. This is often discovered during clutch replacement or when oil drips appear under the rear of the car.

This issue also affects: Porsche Cayman, Porsche Boxster

Common Symptoms

  • Oil drip from bellhousing area
  • Burning oil smell from rear of car
  • Clutch slipping due to oil contamination
  • Oil spots on garage floor near rear axle
  • Visible oil on flywheel during inspection

How to Fix

Replace the rear main seal. This requires transmission removal and is commonly done alongside clutch replacement and IMS bearing upgrade to save labor costs. Use the updated Porsche OEM seal design.

What you need to fix it

Only diagnosis- and fitment-reviewed repair parts are linked here.

  • Genuine Porsche 0PB105249 updated PTFE rear main seal

    1999-2008 Porsche 911 996/997 M96/M97 applications after VIN/engine confirmation; 0PB105249 supersedes 99710121200 and 99911349040. Excludes 2009-2019 MA1 engines.

    LN Engineering

As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.

Owner tips & cautions

  • TipAlways replace the RMS when doing a clutch job — the labor overlap saves $1,000+. Bundle with IMS bearing replacement on 996/997 cars.
Typical repair cost:$1,500 - $3,500

Research This Issue

Based on 3,800 owner reports

GoogleRedditYouTubeNHTSA
Community Reported
High Confidence3,800 owner reportsLast reported by owners Dec 2025Reviewed Mar 2026
Community reported
2,800 owners

On the 1999-2008 Porsche 911, the AOS diaphragm on M96/M97 engines ruptures over time, causing unmetered air leaks into the intake manifold and excessive oil consumption. The failed AOS allows oil vapor to be drawn directly into the intake system rather than being separated and returned to the crankcase. This leads to rich running, fouled spark plugs, and smoke from the exhaust.

This issue also affects: Volkswagen Passat, Audi A4, Audi A5

Common Symptoms

  • Excessive oil consumption
  • White or blue smoke from exhaust
  • Rough idle and vacuum leak symptoms
  • Oil fouled spark plugs
  • Strong oil smell in cabin with heat on

How to Fix

Replace the AOS unit. Use an updated OEM Porsche unit or aftermarket upgrade from LN Engineering. The AOS is located in the engine V between the cylinder banks and requires moderate disassembly to access.

What you need to fix it

Only diagnosis- and fitment-reviewed repair parts are linked here.

  • Genuine Porsche 99610702355 air-oil separator

    Confirm hose/clamp requirements and exclude Turbo/GT models.

    FCP Euro
  • Genuine Porsche 99610702652 air-oil separator

    Confirm exact VIN and exclude 3.8L S/Turbo/GT branches.

    FCP Euro
  • Genuine Porsche 99710703801 primary oil separator

    2005-2008 Porsche 997 Carrera S, 2006-2008 Carrera 4S and applicable 2007-2008 Targa 4S 3.8L; 99710703801 supersedes 99710703800. Not the separate secondary separator.

    FCP Euro

As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.

Typical repair cost:$500 - $1,500

Research This Issue

Based on 2,800 owner reports

GoogleRedditYouTubeNHTSA
Community Reported
High Confidence2,800 owner reportsLast reported by owners Nov 2025Reviewed Mar 2026
NHTSA Recalls7 recalls

AIR BAGS: AIR BAG/RESTRAINT CONTROL MODULE

Porsche Cars North America, Inc. (Porsche) is recalling certain 2016-2017 911 and Boxster, 2016 Cayman and Panamera vehicles. The air bag Electronic Control Unit (ECU) may have a defective power supply capacitor that can result in air bag deactivation or inadvertent deployment of the air bags.

Campaign #19V53300017/07/2019

AIR BAGS:SIDE/WINDOW

Porsche Cars North America, Inc. (Porsche) is recalling certain model year 2017 718 Boxster, 718 Boxster S, 718 Cayman, 718 Cayman S, 911 Carrera, 911 Carrera S, 911 Carrera S Cabriolet, 911 Carrera 4S, 911 Turbo, 911 Turbo S, 911 Carrera 4S Cabriolet, and 911 Turbo Cabriolet vehicles. The seat mounted side air bag inflator initiator may fail to ignite during a crash.

Campaign #16V94600030/12/2016

VISIBILITY:WINDSHIELD

Porsche Cars North America, Inc. (Porsche) is recalling certain 2017 911 Carrera Cabriolet, 911 Carrera 4 Cabriolet, 911 Carrera 4S Cabriolet, 911 Carrera S Cabriolet, 911 Targa S, 911 Targa 4S, 911 Turbo Cabriolet, 718 Boxter and 718 Boxter S vehicles. During manufacturing, the windshield may not have been properly bonded to the vehicle, allowing it to detach in a crash. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 212, "Windshield Mounting."

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Frequently Asked Questions

What are the most common Porsche 911 problems?

According to Au7o's analysis of 12,100+ owner reports, the 2004 Porsche 911 has 3 documented issues. The most frequently reported are: Intermediate Shaft (IMS) Bearing Failure, Rear Main Seal (RMS) Oil Leak, Air-Oil Separator (AOS) Failure. Of these, 1 is rated critical and should be addressed promptly.

Is the Porsche 911 reliable?

The 2004 Porsche 911 has 3 known issues documented across 12,100+ owner reports. 1 issue is rated critical: Intermediate Shaft (IMS) Bearing Failure. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common Porsche 911 problems?

Repair costs for known Porsche 911 issues range from $500 to $4,500, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, Intermediate Shaft (IMS) Bearing Failure, typically costs $2,000-$4,500 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 1999-2008 Porsche 911 Intermediate Shaft (IMS) Bearing Failure?

The IMS bearing on 996 and early 997 flat-six engines is a single-row or dual-row sealed bearing that loses lubrication over time, leading to catastrophic bearing failure and engine destruction. The dual-row bearing (1999-2005) fails less frequently than the single-row (2006-2008… Repairs typically run $2,000-$4,500. Severity: high.

What is the 1999-2019 Porsche 911 Rear Main Seal (RMS) Oil Leak?

The rear main seal on the M96, M97, and MA1 flat-six engines is prone to leaking oil onto the clutch and flywheel. The seal hardens over time and the flange design allows oil to migrate past the seal. This is often discovered during clutch replacement or when oil drips appear und… Repairs typically run $1,500-$3,500. Severity: medium.

Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.

Data sourced from 12,100+ owner reports, NHTSA recalls, TSBs, and automotive forums.

Campaign #17V13500002/03/2017

SUSPENSION:REAR

Porsche Cars North America, Inc. (Porsche) is recalling certain 2019 Porsche 911 Speedster, 2020 Porsche 911 Carrera S Coupe, Carrera 4S Coupe, and Carrera S Cabriolet vehicles. The screw connection on the rear axle upper control arm may be loose.

Campaign #21V20100024/03/2021

AIR BAGS

Porsche Cars North America, Inc. (Porsche) is recalling certain 2018 718 Boxster, Boxster S and Boxster GTS, 718 Cayman, Cayman S and Cayman GTS, 911 Carrera, Carrera T, Targa 4 GTS, Carrera 4, Carrera S, Carrera 4S, Carrera GTS, Carrera 4 GTS, Carrera Cabriolet, Carrera S Cabriolet, Carrera 4S Cabriolet, Carrera GTS Cabriolet, Carrera 4 GTS Cabriolet, Targa 4, Targa 4S, Turbo, Turbo S, Turbo S Exclusive Series, Turbo Cabriolet, Turbo S Cabriolet and GT3 vehicles. The side air bag impact sensors may not have been properly tightened to the vehicle.

Campaign #19V17900006/03/2019

+ 2 more recalls. Check all on NHTSA.gov

Enter your VIN at NHTSA.gov to check recalls specific to your vehicle.

What is the 1999-2008 Porsche 911 Air-Oil Separator (AOS) Failure?

The AOS diaphragm on M96/M97 engines ruptures over time, causing unmetered air leaks into the intake manifold and excessive oil consumption. The failed AOS allows oil vapor to be drawn directly into the intake system rather than being separated and returned to the crankcase. This… Repairs typically run $500-$1,500. Severity: medium.