Water draining/ rickling sound 308 - Strange Issue

[Tony-Danger]

Weird one this. I've got a 308 2016 1.5 Diesel. When I start the car up, if I rev the engine above around 2.5k you can hear a sound coming from behind the glovebox that sounds like water pouring through a pipe.

After 2 or 3 revs it stops and behaves as it should.

Initially the engine was heating up incredibly quickly, however after a full coolant flush and new stuff put in, it runs at correct temp and doesn't heat up to fast. The noise is still there though.

My garage isn't sure what it could be. Theyve suggested:
Failing water pump
Airlock
Failing Head Gasget
Failing Thermostat

But they really are not sure & I don't fancy paying them to try a shot in the dark each time.

Anyone else had a similar issue? I'd rather my garage not go a crapshoot of guesses at my cost to try and figure it out.

[TooLateForAName]

Isnt the bleed valve at the back of the engine on these? was it bled properly?

[drdino]

Is the coolant level stable?

I'd make sure there's no air in the system, my 307 and 308 both mentioned a process where you fitted a container on top of the expansion tank and filled it with coolant; this raised the level higher that the highest point of the circuit (the pipes that go to the cabin radiator) and you then ran the engine until it got to temperature and the stat opened.

[Tony-Danger]

TooLateForAName said:

Isnt the bleed valve at the back of the engine on these? was it bled properly?

I assume so. Local garage gave it a full flush and then put new coolant in.

[Tony-Danger]

drdino said:

Is the coolant level stable?

I'd make sure there's no air in the system, my 307 and 308 both mentioned a process where you fitted a container on top of the expansion tank and filled it with coolant; this raised the level higher that the highest point of the circuit (the pipes that go to the cabin radiator) and you then ran the engine until it got to temperature and the stat opened.

Yep, it's stable. Garage did notice a small amount of bubbles going through the system, but not sure why.

[Twig62]

I think you need to take it to another garage as the one you have used don't seem to know much or do not want to get involved with it

[GreenV8S]

You'll have an air lock somewhere because it wasn't filled and vented properly. You would need to either find somewhere who knows the correct fill/vent procedure for that installation, or wait (maybe for a very long time) for it to disperse naturally.