Hello, first time posting.
 

Can someone identify this noise please? Occurred today after turning engine off. 2.0 turbo diesel. 
 

I just bought a second hand Yeti 3 weeks ago. Love the car but already had a stuck clutch pedal fixed on warranty. I got the timing belt and water pumped replaced at same time. Just got car back and it made this noise today. 

 

Any info would be appreciated.

 

Thanks

Iain 

Might be fans running to cool after switching off midway through regen?

Hi Freedie, I’m a car novice, what’s a regen?

 

To me it sounds like a faulty pump of some sort. But I don’t know. 
 

I’ve heard fans running after engines turned off before but this sounded extreme. 

Hi Iain81

 

The noise sounds like a tyre inflator pump, but it's clearly not that. The fuel system pump(s) shouldn't carry on after switch off.  The radiator fans make more of a roaring noise, and if you open the bonnet you can see and feel them going. But there is an auxiliary electrically operated water pump which carrys on circulating coolant after switch off, to avoid heat soak.  I suggest you try and locate it and see if the noise is coming from there (it shouldn't be anywhere near that loud by the way).  Sometimes a length of plastic or rubber hose is useful as a stethoscope, put one end to your ear and "explore" with the other end.

Hi Austin, 

 

Thanks for that. Would that be the water pump that is installed with the timing belt? 
 

I will play the video to my mechanic and see if he has any ideas. It’s certainly loud. As I have a 3 month warranty I would like to get it diagnosed asap.  
 

After looking up regen after previous comment I’m worried about a faulty particulate filter. 

Hi

 

The main water pump is mechanically driven by the timing belt and is the one that's often replaced at the same time as the belt. It only runs when the engine is running. 

 

The auxiliary water pump is electrically driven, so that if the engine is quite hot the coolant can still be circulated for a while after the engine has stopped.  I suspect that it can also be switched on automatically to boost circulation if the coolant is especially hot and the engine is running but not very fast, e.g. idling in traffic.

 

IF it is the auxiliary water pump making the noise, it suggests that something has failed and is causing internal rubbing, or some foreign object in the coolant has come to rest inside it.

Thanks for your insight. 

Do all the engines have the auxiliary water pump or is it just the petrol ones?

 

I am gradually getting to know what all the alien looking parts are that smother my engine and have not yet seen anything resmbling a water pump.

3 hours ago, J.R. said:

Do all the engines have the auxiliary water pump or is it just the petrol ones?

 

I am gradually getting to know what all the alien looking parts are that smother my engine and have not yet seen anything resmbling a water pump.

 

Afaik, if your car has a turbocharger then there is an electric auxiliary pump that continues to pump coolant for around one minute after ignition is switched off or engine has stopped. Its main job is to cool the turbo (bearings) after engine stops.  Its usually quite quiet and a just high pitch hum. If you look at the coolant reservoir you can often see the coolant being pumped back during this period.

 

Some engines have two auxiliary electric pumps, they are not easy to spot, buried in the pipework behind or under the engine and quite small. I think the second pump is to pump coolant round the internal heater, as some cars (eg Superb) have a function where the heater continues to work on residual heat when the engine has stopped, for instance in stop/start mode or if the driver selects rest mode on the heater..

 

Other buzzes and clicks can be from the electric turbo actuator which does some stuff on power down as well as start up.

Water cooling turbo bearings did not sound plausible to me, an auxiliary oil pump yes, but water at turbo temperatures??????????

 

But I checked and you are correct, the article could have been written for me!

 

this Garrett white paper will hopefully convince a skeptic that the benefits provided by water-cooling are worth the small effort required to properly set it up.

 

https://www.garrettmotion.com/fr/racing-and-performance/choosing-a-turbocharger/water-cooling-for-your-turbo/

 

Do the stock VAG diesel turbos have this water cooling?

Don't know, you'll have to check somewhere like 7zap.com and look at the parts list for the coolant and turbo sections

On 07/04/2021 at 18:34, J.R. said:

Water cooling turbo bearings did not sound plausible to me, an auxiliary oil pump yes, but water at turbo temperatures??????????

 

But I checked and you are correct, the article could have been written for me!

 

this Garrett white paper will hopefully convince a skeptic that the benefits provided by water-cooling are worth the small effort required to properly set it up.

 

https://www.garrettmotion.com/fr/racing-and-performance/choosing-a-turbocharger/water-cooling-for-your-turbo/

 

Do the stock VAG diesel turbos have this water cooling?

 

On the later EA288 there are three water circuits, one mechanically driven pump that has a solenoid for adjusting flow and two electric water pumps. The turbo is oil cooled but there is an oil/water heat exchanger.

 

https://pics.tdiclub.com/data/517/820433_EA288.pdf

Thanks for that, I will print it out and profit from my insomnia, I have already learned a lot from scanning through the first part, there is a lot of clever tech in our engines. Now I know why my vehicle warms up quicker than preceeding TDi's and why the heater puts out heat so early.

 

To Xman, the auxiliary electric water pumps definitely do not cool the turbo bearings, if one runs after shut off and if it circulated through the oil cooler then it would not do anything for the turbo unless there was an electric pump circulating said oil through the turbo bearings.

3 minutes ago, J.R. said:

To Xman, the auxiliary electric water pumps definitely do not cool the turbo bearings, if one runs after shut off and if it circulated through the oil cooler then it would not do anything for the turbo unless there was an electric pump circulating said oil through the turbo bearings.

 

I think the philosophy is the turbo is sufficiently temperature controlled while the engine is running that heat soak when the engine is turned off by Stop/Start or human is not detrimental. 

42 minutes ago, J.R. said:

 

To Xman, the auxiliary electric water pumps definitely do not cool the turbo bearings, if one runs after shut off and if it circulated through the oil cooler then it would not do anything for the turbo unless there was an electric pump circulating said oil through the turbo bearings.

 

I was referring to TSI petrol engines which do have water and oil cooling on the turbo with run on after switch off.

 

EA211 Page 23 of SSP 511

 

SSP-511_The_New_EA211_Petrol_Engine_Family.pdf

 

Also EA888 SSP606  page 31

 

SSP606 link

 

Thought it might be the same for all current engines but stand corrected as far as EA288 diesel engines. Apologies, but now we know....

 

Edited 9 April, 20215 yr by xman

OK, understood, I was asking about diesel engines.

 

All knowledge is relevant and welcome!

Exhaust gas temperatures are far higher on petrol models.

Update:

 

Car had new clutch fitted last week and a loose bracket was not secured and was rubbing against the fan. 
 

Quick cheap fix thankfully. 
 

Thanks for all who commented.