Losing coolant: water pump and thermostat housing leaks

Which cars and engines are affected?

This page covers coolant loss and related cooling faults on Audi, Volkswagen, SEAT and Škoda cars. For other work on these cars, see our Audi and VW specialist page.

• Petrol. Audi has published technical guidance on leaks from the water pump and the thermostat housing on later generations of its EA888 petrol engine. Put your registration in the enquiry form and we will check which engine your car has.
• Diesel. Some 1.6 and 2.0 TDI engines have a water pump controlled by the engine control unit. Its faults cause overheating with no leak, and are often misread as a thermostat or head gasket fault.
• Coolant loss with no visible leak. On diesels this can be an internal leak in the EGR cooler. See our EGR valve and cooler page.

What are the symptoms?

On EA888 petrol engines with a pump or housing leak:

• a low coolant warning
• coolant on the ground under the car

On TDI engines with a sticking electronic water pump:

• the temperature gauge reading above 110 °C
• poor heating inside the car
• cooling system fault codes
• overheating at low speed, with no external leak

What causes it?

• Petrol: a leak at the water pump or the thermostat housing. Coolant escapes from the pump’s weep hole or past the thermostat housing seal.
• Diesel: a sticking electronic water pump. The pump’s control collar can seize or its impeller can fail, and deposits can jam the shutter ring. The engine then overheats with no leak, and the fault is often misread as a thermostat or head gasket problem.
• Internal leaks. An EGR cooler leak, a head gasket fault or a cracked cylinder head can all lose coolant with nothing visible outside the engine.

How do you confirm the fault before fitting parts?

A fault code is not a repair, and a wet engine bay does not tell you which part is leaking. Before we quote for any parts, we:

• pressure-test the cooling system and find the exact leak point
• check whether the leak is at the water pump weep hole, the thermostat housing seal or both
• on TDI engines that overheat, check the coolant flow at the header tank return pipe
• where there is no visible leak, test for an internal leak before recommending any repair

We then show you what we found, with photos, and send a written price. No part is fitted until you give your written approval.

What does the repair involve?

• Water pump leak: we replace the pump only when the leak is at its weep hole.
• Thermostat housing leak: we repair the leak at the housing. We do not replace the pump and housing together unless both leaks are proven, and we always fit a new seal.
• TDI electronic pump: we fit an improved or conventional replacement pump, transfer the solenoid valve where needed, flush the system fully, refill with the correct coolant and bleed out the air.

Once the work is done, we pressure-test again, check that the leak or overheating has gone and verify the repair, including a road test where appropriate.

How long does a coolant leak repair take?

It depends on where the leak is and which part has to be replaced.

Before any work starts, you get a written price and a promised time for your next update. If the car needs to stay with us, ask about a courtesy car when you book.

Is there a recall for coolant leaks?

DVSA does list two Audi recalls for a different part, the electric auxiliary coolant pump, so check these first:

• R/2017/115: Audi A4, A5, A6 and Q5 built from May 2011 to October 2016.
• R/2018/152: Audi A4 and A5 built from May 2011 to May 2017.

Whether a recall applies depends on the individual car, so check your registration on gov.uk. Recall work is done by the manufacturer’s network, not by us.