1990 model year · 0+ owner reports · Updated April 2026
According to Au7o's analysis of 0+ owner reports, the 1990 Audi 100 has 4 documented known issues, with 2 rated critical. The most serious are Power Steering Rack Seal Leak ($500-$1,200 repair) and Hydraulic Assist System Leak (Pentosin) ($500-$2,000 repair). Across all issues, repair costs range from $50 to $2,500. DIY maintenance guides at au7o.io.
On the 1990-1994 Audi 100, the hydraulic power steering rack develops leaks from the input shaft seal and inner tie rod boots. Pentosin hydraulic fluid weeps and eventually pours from the rack, causing heavy steering and low fluid warnings.
Replace or rebuild power steering rack. Use Pentosin CHF 11S fluid only — conventional ATF will destroy seals. Flush entire system when replacing rack. Check pump for whining which indicates damage from running low.
Parts and tips from 0+ owners who fixed this issue
On the 1990-1994 Audi 100, the Audi 100 uses a complex mineral oil hydraulic system (Pentosin) that powers steering, brakes, and self-leveling suspension. Hoses, pump seals, and rack seals develop leaks, causing loss of power assist to steering and brakes simultaneously.
Parts and tips from 0+ owners who fixed this issue
On the 1990-1994 Audi 100, the Audi 100/200 automatic transmission develops harsh shifting patterns and delayed engagement. The multi-plate clutches and valve body solenoids wear, particularly in higher-mileage examples.
Parts and tips from 0+ owners who fixed this issue
On the 1990-1994 Audi 100, vacuum hoses throughout the engine bay become brittle, crack, and leak with age. Causes rough idle, failed emissions, inoperative climate control flaps, and cruise control failure. The Audi 100 uses vacuum for numerous subsystems.
Replace all vacuum hoses with silicone or OEM-quality rubber hose. Create a vacuum line diagram before removing old lines. Test each vacuum-operated system after replacement. Inspect check valves and vacuum reservoir.
Parts and tips from 0+ owners who fixed this issue
FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM
VEHICLE DESCRIPTION: PASSENGER VEHICLES EQUIPPED WITH V6 ENGINES. AN INTERNAL SEAL OF THE FUEL INJECTOR CAN MALFUNCTION, ALLOWING FUEL LEAKAGE IN THE ENGINE COMPARTMENT.
EQUIPMENT:ELECTRICAL:RADIO/TAPE DECK/CD ETC.
VEHICLE DESCRIPTION: PASSENGER VEHICLES. AN ELECTROLYTIC CAPACITOR CONTAINED IN THE AMPLIFIER FOR EACH REAR SPEAKER COULD LEAK AN ELECTROLYTE, WHICH MAY IN TIME AND IN THE PRESENCE OF HUMIDITY, CAUSE AN UNWANTED CONDUCTIVE PATH.
EQUIPMENT:MECHANICAL:ACCESSORY SCISSOR/SCREW/BOTTLE JACK/LIFT
INSTRUCTION LABEL IN THE TRUNK OF VEHICLE IS INCORRECT FOR THE JACK SUPPLIED WITH THE VEHICLE.
FUEL SYSTEM, GASOLINE:DELIVERY:HOSES, LINES/PIPING, AND FITTINGS
VEHICLE DESCRIPTION: PASSENGER VEHICLES. THE FUEL FEED LINE CONNECTING THE FUEL FILTER TO THE ENGINE DELIVERED BY THE SUPPLIER FOR USE IN THESE VEHICLES MAY HAVE BEEN IMPROPERLY MANUFACTURED.
ELECTRICAL SYSTEM:IGNITION:SWITCH
DEFECTIVE IGNITION SWITCHES WERE IMPROPERLY MANUFACTURED AND CAN CAUSE SOME ELECTRICAL ACCESSORIES TO MALFUNCTION.
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According to Au7o's analysis of 0+ owner reports, the 1990-1990 Audi 100 has 4 documented issues. The most frequently reported are: Power Steering Rack Seal Leak, Hydraulic Assist System Leak (Pentosin), Automatic Transmission Harsh Shifting. Of these, 2 are rated critical and should be addressed promptly.
The 1990-1990 Audi 100 has 4 known issues documented across 0+ owner reports. 2 issues are rated critical: Power Steering Rack Seal Leak and Hydraulic Assist System Leak (Pentosin). 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.
Repair costs for known Audi 100 issues range from $50 to $2,500, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, Power Steering Rack Seal Leak, typically costs $500-$1,200 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
The hydraulic power steering rack develops leaks from the input shaft seal and inner tie rod boots. Pentosin hydraulic fluid weeps and eventually pours from the rack, causing heavy steering and low fluid warnings. Repairs typically run $500-$1,200. Severity: high.
The Audi 100 uses a complex mineral oil hydraulic system (Pentosin) that powers steering, brakes, and self-leveling suspension. Hoses, pump seals, and rack seals develop leaks, causing loss of power assist to steering and brakes simultaneously. Repairs typically run $500-$2,000. Severity: high.
The Audi 100/200 automatic transmission develops harsh shifting patterns and delayed engagement. The multi-plate clutches and valve body solenoids wear, particularly in higher-mileage examples. Repairs typically run $300-$2,500. Severity: medium.
Vacuum hoses throughout the engine bay become brittle, crack, and leak with age. Causes rough idle, failed emissions, inoperative climate control flaps, and cruise control failure. The Audi 100 uses vacuum for numerous subsystems. Repairs typically run $50-$200. 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.
