2018 Audi S5 Problems: 4 Issues Every Owner Should Know

2018 model year · 497+ owner reports · Updated April 2026

According to Au7o's analysis of 497+ owner reports, the 2018 Audi S5 has 4 documented known issues, with 1 rated critical. The most serious is EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T) ($1,200-$3,500 repair). The most commonly reported issue is Thermostat and Water Pump Assembly Failure with 211 owner reports. Across all issues, repair costs range from $300 to $3,500. DIY maintenance guides at au7o.io.

All 4 Known Issues

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When Issues Typically Appear

EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T)

40K-70K

Direct Injection Carbon Buildup

40K-60K

Thermostat and Water Pump Assembly Failure

60K-80K

025K50K75K100K mi

On the 2018-2024 Audi S5, the B9/B9.5 Audi S5 (2018-2024) with the EA839 2.9T twin-turbo V6 suffers from a particularly insidious water pump failure. Unlike typical water pumps that leak externally, the EA839 water pump leaks INTERNALLY. The pump uses vacuum to operate a slide valve controlling impeller actuation. When the internal seals fail, coolant is drawn into the vacuum system and migrates into other components where coolant should never be present—including the brake booster, turbo wastegate actuators, and other vacuum-operated systems. This makes the failure especially dangerous as it can affect braking and boost control simultaneously. New German Performance and AudiWorld forums describe this as a 'when, not if' failure on EA839 engines. Failures typically occur between 40,000-70,000 miles.

This issue also affects: Volkswagen Eurovan, Audi A3, Audi A6

Common Symptoms

Coolant level dropping with no visible external leak
Sweet coolant smell but no puddle under car
Brake pedal feels soft or spongy (coolant in brake booster)
Turbo boost irregularities (coolant in wastegate actuator vacuum lines)
Check engine light with coolant temperature or boost codes
White residue in vacuum lines when inspected
Engine overheating warning

How to Fix

Replace water pump assembly with UPDATED revision ($1,200-$2,500 installed). The EA839 water pump replacement requires significant disassembly—5-8 hours of labor. CRITICAL: Inspect ALL vacuum lines, brake booster, and wastegate actuators for coolant contamination. If coolant entered the brake booster, replace it immediately ($800-$1,500)—this is a SAFETY issue. Flush the vacuum system thoroughly. Use OEM replacement pump with updated seals. PREVENTION: Monitor coolant level monthly. If coolant drops with no visible leak, suspect internal water pump failure immediately.

What Owners Are Using

Parts and tips from 0+ owners who fixed this issue

UpgradeOEM EA839 water pump with updated internal seals. Check for latest revision number from your Audi parts counter. Earlier revisions are more failure-prone. (Genuine VW/Audi EA839 Water Pump Assembly (Updated))
View on Amazon
NoteThis is NOT a typical water pump leak. Coolant enters the vacuum system and can contaminate your brake booster. If you notice a soft brake pedal AND dropping coolant, get this inspected IMMEDIATELY—it is a safety issue.
TipWhen replacing the water pump, have the shop inspect all vacuum lines for white coolant residue. Any contaminated lines or actuators must be replaced or flushed.

Typical repair cost:$1,200 - $3,500

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0+ owners have reported this issue

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Community Reported

Medium Confidence0 reportsLast reported by owners Invalid DateReviewed Invalid Date

Community Reported

184 owners

On the 2008-2025 Audi S5 3.0T, the water-to-air intercooler system on the S5 3.0T uses an electric coolant pump that can fail, causing elevated charge air temperatures and reduced power. Heat soak becomes severe in warm climates.

This issue also affects: Audi A5, Audi A6 allroad, Audi A7

Common Symptoms

Heat soak power loss
Reduced boost performance
Intercooler pump fault code
Elevated intake temps
Sluggish acceleration in heat
Check engine light

How to Fix

Replace intercooler coolant pump. Check intercooler lines for leaks and flush the circuit during replacement.

What Owners Are Using

Parts and tips from 184+ owners who fixed this issue

UpgradeIntercooler Coolant Pump (Pierburg #7.02078.37.0)
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Typical repair cost:$300 - $700

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184+ owners have reported this issue

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Community Reported

High Confidence184 reportsLast reported by owners Mar 2026Reviewed Mar 2026

Community Reported

102 owners

On the 2008-2025 Audi S5, the S5 suffers from carbon deposit accumulation on intake valves common to all Audi direct-injected engines. The performance-oriented tuning makes power loss from carbon more noticeable than in base models.

Common Symptoms

Rough idle
Power loss
Cold start misfires
Hesitation under load
Check engine light
Poor throttle response

How to Fix

Walnut blast intake valves every 40,000-60,000 miles. Install oil catch can to reduce oil vapor reaching valves.

What Owners Are Using

Parts and tips from 102+ owners who fixed this issue

UpgradeOil Catch Can Kit (034Motorsport #034-101-1000)
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Typical repair cost:$400 - $900

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102+ owners have reported this issue

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Community Reported

High Confidence102 reportsLast reported by owners Mar 2026Reviewed Mar 2026

Community Reported

211 owners

On the 2008-2025 Audi S5 3.0T, the S5 3.0T thermostat and water pump assembly uses a plastic housing that degrades over time. Leaks develop at the housing seams and O-ring seals, often around 60,000-80,000 miles.

This issue also affects: Audi A5, Audi A6 allroad, Audi A7

Common Symptoms

Coolant leak at rear of engine
Overheating
Low coolant warning
Temperature gauge spikes
Sweet coolant smell
Steam from engine bay

How to Fix

Replace thermostat/water pump assembly. Upgrade to revised housing if available.

What Owners Are Using

Parts and tips from 211+ owners who fixed this issue

UpgradeWater Pump and Thermostat Kit (Graf #PA1273)
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Typical repair cost:$400 - $1,000

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211+ owners have reported this issue

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Community Reported

High Confidence211 reportsLast reported by owners Mar 2026Reviewed Mar 2026

Frequently Asked Questions

What are the most common Audi S5 problems?

According to Au7o's analysis of 497+ owner reports, the 2018-2018 Audi S5 has 4 documented issues. The most frequently reported are: EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T), Thermostat and Water Pump Assembly Failure, 3.0T Supercharger Intercooler Pump Failure. Of these, 1 is rated critical and should be addressed promptly.

Is the Audi S5 reliable?

The 2018-2018 Audi S5 has 4 known issues documented across 497+ owner reports. 1 issue is rated critical: EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T). 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 Audi S5 problems?

Repair costs for known Audi S5 issues range from $300 to $3,500, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T), typically costs $1,200-$3,500 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 2018-2024 Audi S5 EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T)?

The B9/B9.5 Audi S5 (2018-2024) with the EA839 2.9T twin-turbo V6 suffers from a particularly insidious water pump failure. Unlike typical water pumps that leak externally, the EA839 water pump leaks INTERNALLY. The pump uses vacuum to operate a slide valve controlling impeller a… Repairs typically run $1,200-$3,500. Severity: high.

What is the 2008-2025 Audi S5 Thermostat and Water Pump Assembly Failure?

The S5 3.0T thermostat and water pump assembly uses a plastic housing that degrades over time. Leaks develop at the housing seams and O-ring seals, often around 60,000-80,000 miles. Repairs typically run $400-$1,000. Severity: medium.

What is the 2008-2025 Audi S5 3.0T Supercharger Intercooler Pump Failure?

The water-to-air intercooler system on the S5 3.0T uses an electric coolant pump that can fail, causing elevated charge air temperatures and reduced power. Heat soak becomes severe in warm climates. Repairs typically run $300-$700. Severity: medium.

What is the 2008-2025 Audi S5 Direct Injection Carbon Buildup?

The S5 suffers from carbon deposit accumulation on intake valves common to all Audi direct-injected engines. The performance-oriented tuning makes power loss from carbon more noticeable than in base models. Repairs typically run $400-$900. Severity: medium.

2018 Audi S5 Problems: 4 Issues Every Owner Should Know

All 4 Known Issues

When Issues Typically Appear

2018-2024 Audi S5: EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T)#

Common Symptoms

How to Fix

What Owners Are Using

Research This Issue

2008-2025 Audi S5: 3.0T Supercharger Intercooler Pump Failure#

Common Symptoms

How to Fix

What Owners Are Using

Research This Issue

2008-2025 Audi S5: Direct Injection Carbon Buildup#

Common Symptoms

How to Fix

What Owners Are Using

Research This Issue

2008-2025 Audi S5: Thermostat and Water Pump Assembly Failure#

Common Symptoms

How to Fix

What Owners Are Using

Research This Issue

Other Audi Models

Frequently Asked Questions

What are the most common Audi S5 problems?

Is the Audi S5 reliable?

How much does it cost to fix common Audi S5 problems?

What is the 2018-2024 Audi S5 EA839 Water Pump Internal Leak and Vacuum System Contamination (2.9T)?

What is the 2008-2025 Audi S5 Thermostat and Water Pump Assembly Failure?

What is the 2008-2025 Audi S5 3.0T Supercharger Intercooler Pump Failure?

What is the 2008-2025 Audi S5 Direct Injection Carbon Buildup?