Why is my Audi A4 (B9) losing coolant from the water pump area?

Short answer: On the B9 A4 2.0T, a low coolant message plus dried pink crust under the engine usually means the plastic water pump/thermostat housing is leaking. Confirm with a pressure test, then replace the assembly.

Symptom: A low coolant warning, coolant below MIN, a sweet smell after driving, or dried pink residue under the water pump with no real puddle.

What to check first

1. Check the coolant level cold, against the MIN and MAX marks.
2. Look for dried pink or white crust under the intake side of the engine, below the water pump.
3. Ask the shop to pressure-test (and use UV dye if needed) to find the leak.
4. Ask Audi whether your car qualifies for any water pump coverage or settlement reimbursement.

Likely causes

1. Water pump / thermostat housing leak. On the EA888 2.0T, the water pump and thermostat sit together in a plastic housing. Its seals and plastic can leak, often leaving dried pink crust instead of a puddle.
2. Rear coolant pipe or auxiliary water pump. A coolant pipe with a white plastic fitting at the back of the engine and the small auxiliary water pump are other common leak points that owners mention.
3. Coolant level sensor or reservoir. Sometimes the warning is a sensor or tank problem. A pressure test separates a real leak from a false warning.

What it usually costs

Shops replace the water pump and thermostat as one assembly, and labor is a big part of the bill. Ask Audi about settlement or goodwill coverage before you pay out of pocket.

Is it safe to keep driving?

If the gauge is normal and the leak is slow, keep it topped up and get it in soon. If the temperature climbs or a red warning appears, stop and tow it.

DIY or shop?

Checking and topping up is DIY. The pump job is doable for experienced DIYers, but most owners use a shop.

Recalls, bulletins and complaints in plain words

• Related recalls: NHTSA lists these recalls touching this area of the Audi A4: 22V368000 (2022-2022 model years, engine and engine cooling:engine:engine control module (ecu/ecm)). Check your VIN at nhtsa.gov/recalls. If your car is part of this recall, the dealer fixes it for free.
• Plain words: The complaint count below shows how often owners reported problems that mention these words to NHTSA. A count is not proof of a defect.
• NHTSA complaints: 26 keyword-matched complaints for Audi A4 2017–2024 (of 273 unique complaints queried, NHTSA complaints API by model year, queried 2026-11-07; keywords: coolant, water pump, thermostat, leak, overheat) (NHTSA returned no data for 4 model-year queries). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Do I have the dreaded leaky water pump? A4 B9 2019 on Reddit r/Audi, a 2019 A4 owner with about 64,000 miles came home from vacation to a low coolant message and a level far below MIN, with a dry coolant spot under the water pump. He wanted to confirm it was the pump before asking Audi to cover it under the settlement.
• In B9 A4 leak on Reddit r/AudiA4, a B9 A4 2.0T quattro owner posted a leak at the back of the engine. Replies pointed to the coolant pipe with a white plastic fitting and the auxiliary water pump as common failure points, with a repair of around $800 mentioned.

Quick tip

On B9 A4s, don't wait for a puddle. Dried pink crust under the pump means the leak has started.

Vehicle focus: Audi A4 (B9) 2.0T (EA888), 2017–2024. The A5 shares this engine.

Safety / mechanic note

Low coolant can overheat a turbo engine fast. Verify with a mechanic.