I’ve got a recurring fault on my Audi and trying to work out if anyone’s had the same.

Code is 33688 – Coolant Pump 2 mechanical malfunction, which looks to point to the auxiliary coolant pump or its control.

This first came up after a low coolant warning. I ended up adding about a litre of coolant (so there is a leak) and since then the level has stayed stable and hasn’t dropped again.

The fault code keeps coming back even after clearing it. No overheating, temperature sits bang on normal, car drives as it should.

So at the moment it feels like two things happened at once. Coolant dropped once, now stable, but the pump fault keeps returning.

From what I can see it could be the aux pump starting to fail, or possibly the control side like the solenoid or vacuum lines. How does this link up with a slow leak?

Has anyone had this exact code and symptoms? Did it turn out to be the pump itself or something else?

37 minutes ago, pimmo2000 said:

I’ve got a recurring fault on my Audi and trying to work out if anyone’s had the same.

Code is 33688 – Coolant Pump 2 mechanical malfunction, which looks to point to the auxiliary coolant pump or its control.

This first came up after a low coolant warning. I ended up adding about a litre of coolant (so there is a leak) and since then the level has stayed stable and hasn’t dropped again.

The fault code keeps coming back even after clearing it. No overheating, temperature sits bang on normal, car drives as it should.

So at the moment it feels like two things happened at once. Coolant dropped once, now stable, but the pump fault keeps returning.

From what I can see it could be the aux pump starting to fail, or possibly the control side like the solenoid or vacuum lines. How does this link up with a slow leak?

Has anyone had this exact code and symptoms? Did it turn out to be the pump itself or something else?

Hi its the aux pump if you run them dry they spin round and damage the impeller motor, thats the mechanical bit, they are a plastic piece of crap, it won't overheat as the aux pump only works at the end of the journey if its a high ambient temp and also works if you are working on the coolant system and with the ignition off if you open a door it starts cycling and pumps your coolant all over the floor, work that out.

Steve.

On 4/19/2026 at 6:56 PM, Stevey Y said:

Hi its the aux pump if you run them dry they spin round and damage the impeller motor, thats the mechanical bit, they are a plastic piece of crap, it won't overheat as the aux pump only works at the end of the journey if its a high ambient temp and also works if you are working on the coolant system and with the ignition off if you open a door it starts cycling and pumps your coolant all over the floor, work that out.

Steve.

Thanks, is that the pump they replaced with a better version? I read somewhere about the plastic one being superseded

15 minutes ago, pimmo2000 said:

Thanks, is that the pump they replaced with a better version? I read somewhere about the plastic one being superseded

Hi yes they went over to aluminium bodies and then back to plastic when they found out how much the metal was costing, premium cars, my opinion, they are no better than any other manufacturer they will cut corners wherever they can and charge fortunes for plastic parts.

Steve.

Garage couldn’t find any reason for the loss or the fault code