Coolant loss

[Nadav]

I had to replace the water pump a few months ago.
Since then, I’ve noticed that I’m losing coolant very slowly.
I went to the mechanic, and he said there are no leaks.
Does anyone know what I can do or check before going back?

 

[AlperUtkuCeylan]

I dont know why that happens but I have exactly the same problem with my Toledo 1.4tsı

 

[Nadav]

I dont know why that happens but I have exactly the same problem with my Toledo 1.4tsı

When replaced the water pump the mechanic replaced the thermostat as well or just the water pump ?

 

[SRGTD]

It’s possible you have air trapped in your cooling system after the water pump was replaced and the cooling system was refilled. If so, then any trapped air will be purged over time and the coolant level in the expansion tank will drop as coolant fills the space(s) previously occupied by the trapped air.

 

[Nadav]

It’s possible you have air trapped in your cooling system after the water pump was replaced and the cooling system was refilled. If so, then any trapped air will be purged over time and the coolant level in the expansion tank will drop as coolant fills the space(s) previously occupied by the trapped air.

Appreciate the suggestion, but I really don’t think it’s trapped air at this point.
After the water pump replacement, I filled the coolant, let the car cool down, and adjusted the level properly. A couple of months later, the level dropped again — slowly but clearly.


If it were just air in the system, I’d expect it to settle after a few drives, not keep going down after weeks.
No signs of air now — no overheating, bubbling, or heater issues. Everything runs fine.

 

[AlperUtkuCeylan]

When replaced the water pump the mechanic replaced the thermostat as well or just the water pump ?

Just the pump

 

[guyF20]

I guess its the way these cars work with their complex cooling system.
Mine is a 2liter diesel and sometimes i have to add very little sometimes I dont. What I noticed weather and temperature plays a big part, also driving distance habbits(short or long drives) counts too since regeneration can mess with the coolant level also. If it isnt a big loss of coolant and have to add a little every few months or coolant isnt dark dirty or crudy I wouldnt worry about it.