Coolant circulation pump running.

[wolfie]

Slightly odd one this.

When I turned off the car the other day I could here something whirring under the bonnet I really can't recall ever hearing it before, and I've had the car over 9 years. It continued for about 30 seconds and then shut off, I also heard a relay click under the dash. I went out on a little errand Sunday morning and noticed it did it again. Just seems a little odd that I've never heard it before. I assume it's the Coolant circulation pump continuing to run after I've turned off. Just odd in all the time I've had the car I've never noticed it before!?

I just hope it's not a harbinger of doom and something is getting ready to fail. Car runs fine, no warning lights at all.

Any ideas? as far as I m aware the electric coolant circulation pumps primary function is to service the turbo water flow and heat exchanger??

Strange one.

[john M]

Coolant fan maybe, quite normal to hear it after ignition switch off but not normal after running a little errand.

[wolfie]

Coolant fan maybe, quite normal to hear it after ignition switch off but not normal after running a little errand.

Definitely not a fan, noise was from rear of engine. When I say little errand it was a 20 mins each way run out.

[wolfie]

Not been using the car much at all what with all the Covid restrictions.

Took the car out yesterday and it did the same little trick again. When I turn off the engine there's a clicking of sorts like a actuator is being moved. I didn't get the bonnet up quick enough to pin point the source!! Then a buzz from what sounds like the aux water pump. I also noticed that while it's whirring there is a steady trickle of water back into the header tank which ceases when the whirring stops. (all only lasts about 30 seconds. Which again makes me think it is the aux water pump being energized.) I didn't have the presence of mind to watch it for a few minutes to see if it repeated.

Has me scratching my head a little. I have a cheapo fault code reader and that shows no faults. Car runs fine, other than this little anomaly when it's turned off from warm. In all other respects it appears to run fine.

Gut feeling is it's either the mechanical water pump not being switched between modes or a dodgy temp sensor somewhere, or maybe a stuck thermostat?? Dunno, a bill heading my way I suspect.

[RUM4MO]

The clicking noises with modern petrol engined VW Group cars is just the Throttle Body being moved through its full range of normal movement, maybe a forced auto re-cal between TB and ECU.

The electric water pump is normally just killing off any possibility of over temping of the air/water intercooler and maybe even the turbo.

[wolfie]

The clicking noises with modern petrol engined VW Group cars is just the Throttle Body being moved through its full range of normal movement, maybe a forced auto re-cal between TB and ECU.

The electric water pump is normally just killing off any possibility of over temping of the air/water intercooler and maybe even the turbo.

Cheers, I was actually sitting thinking about what may be the source of the clicking and the TB crossed my mind, though I couldn't think of a reason as to why it might be actuating independently. I thought the only way they could be re-calibrated was with the use of a dedicated scan tool. I wasn't aware they could perform auto-recalibrations, I guess the $64,000 question is what has triggered the behaviour to start? (is something starting to fail?) I've had the car almost 10 years and never heard it before, and I count myself as pretty good at picking up rattles, knocks and whirrs.

I was having a little dig for information relating to the aux water-pump and from what little I can find, as you say it's main function is to get water around the charge cooler & turbo bearings. But I'm not sure whether it is supposed to run constantly or just in 'over-temp' conditions as it's appears to be siamesed/parallel with the main cooling circuit.

If it is over-temp then what could cause that!? VW in their infinite wisdom don't fit a water temp guage to give you a heads up. So far as I can tell you get a warning light when it's boiling nicely... I've checked coolant level and it's rock steady, never moved since the day I bought the car.

Thinking about what could possibly cause it to be running hotter, the only things that spring to mind are dodgy thermostat. From what I can see you change the whole housing as it contains two.

Or main water-pump vacuum flow selector is not working so it's simply not pumping as it should. That could be number of things. Faulty pump, vacuum leak, faulty solenoid, or god forbid something on the ECU side.

Failure in off-state: the engine reaches its operating temperature
more slowly.
• Failure in on-state: the coolant temperature increases to an
unacceptably high level since the coolant pump is unable to
feed in fresh coolant. The exhaust warning lamp K83 comes on.

For my sins I don't own a diagnostic tool other than a rubbish cheapo code reader that is pretty much useless.

Why do they never play up when the suns out??

[RUM4MO]

I think that my last two cars and my wife's current car have all had "run on" electric coolant pumps, to do as the name implies, prevent over heating after the engine has been stopped. As far as I can make out, they seem to get triggered to run at engine switch off if the engine temperature has reached a certain temperature, ie they don't run if I just move the car out of the garage and immediately stop it on the driveway.

It is very easy maybe for some of us to think that you have subliminally ignored this going on up to this point and now having heard it are "zoning in" on that noise, that does happen at times. Though you do seem to not think that this is what is happening and I can understand that.

[wolfie]

It is very easy maybe for some of us to think that you have subliminally ignored this going on up to this point and now having heard it are "zoning in" on that noise, that does happen at times. Though you do seem to not think that this is what is happening and I can understand that.

No mate, makes perfect sense, It may well be I've missed it. But you do get used to you own car and all the little foibles that come with it, I'm pretty sure this is something new happening. As I say car is running well other than noticing this, I guess I will just keep my eye on it and see if anything develops. Time will tell.

Cheers for the pointers, you're always a good sounding board for niggles.

I still fancy having something to hand to do basic diagnostics. Maybe if I'm good Santa will bring me something

[wolfie]

Well I stuck a cheap OBD2/ELM327 reader on and that didn't throw up any faults at all. I did notice that if I simply turn the ignition on/off the throttle body cycles, though the cooling pump does not run. All a bit odd, I'm sure the cycling of the throttle body is new, it's loud enough that I can't believe I've not heard it before. You can heart it from in the car.

[Jay-Jay]

Everytime you turn the ignition ON/OFF, the throttle body automatically performs an adaptation.
The wastegate actuator does the same.
Each of these two components produce specific clicks and buzz noises during its adaptation.
I believe what you hear is the auxiliary coolant pump. I heard mine few times, after very hot summer days and/or spritic drives.
If yours keep working everytime you turn off the engine, even after very calm drive, I'd suspect the coolant system is not working properly and coolant temperatures are a higher than they used to be till now.
You say your car is 9 years old and that coolant level has never lowered since the car was new. This means you never replaced coolant in 9 years.
A 9 years old coolant could be not performing as good as it used to do, causing coolant temperature to be higher and the auxiliary coolant pump to stay active for some time after you end driving your car.
So, before searching for a defective component, I would suggest you to perform a coolant replacement.
Plus to that, I highly suggest you to buy a VCDS cable, since it allows you to check and test almost everything of your car. For example, it lets you manually activate the auxiliary coolant pump. By doing that, you can hear its noise and understand if that is what you hear.

[wolfie]

Cheers Jay-Jay.

Pretty much everything you've said there agrees with what I've been thinking over.

It's an interesting piece of information that the throttle body automatically performs an adaptation each time the ignition is cycled. It's bizarre that I've owned the car as long as I have and not picked up on it.

I hear what you say about getting hold of a VCDS cable, it's been on my 'wish list' for a very long time. Problem with that, is it's become pretty expensive since the licenses have been limited. £225 in the UK (3 vehicles) If it's something that you use regularly it makes sense to buy one. For myself, I'd love one, but it's the first time I've 'needed' one in many years of owning Vdubs. Guess I've been lucky reliability wise. Plus now what with the effects of the Covid restrictions I don't really have money spare at the moment.

What I have done is bought one of the little ELM 327, based Bluetooth OBD2 readers. It's pretty limited but I can see water temp and throttle body position and a few other bits of useful information.

I needed to use the car this morning so plugged it in as I returned. Water temp was 92 which is around what I would expect, and I can see it drop to 86/87 when I rev the engine which is a reasonable indication the water pump at least is working. That would also be a fair indication that should the vacuum ON/OFF switch to the pump have failed, it's failed OPEN so things would generally all be running cooler. So it doesn't appear to be an overheating problem as such, though I suppose it could be a faulty sensor somewhere in the system?

It's an observation/niggle rather than a worry at the moment. Car feels and runs fine. I'm just scratching my head a little as to why I've never noticed it before. It's not beyond the realms of possibility that I have a sticking thermostat. Coolant system is a little complex on the Tsi engines so it could be one or the other circuit may be affected.

I'm not too worried about the coolant being as old as the car. While I'm sure it may have used up some or it's anticorrosion additives, it should still have no issues cooling everything so long as nothing is gummed up or stuck. I can't find any maintenance data that says it's is not life of vehicle. Level's have never moved and it still looks clean and fresh despite it's age. I think refilling the system requires a vacuum fill because of layout and non-return valves scattered around the engine.

I do plan to have a quick look at the throttle body just to see whether it looks like it would benefit from a clean.

[RUM4MO]

@wolfie, I share your concerns about changing coolant on these "multi/split" circuit cooling systems and VW Group not laying down any advice or recommendations on when the coolant should be replaced, okay I have VCDS so if I looked into it, I could probably start electric pump running etc.

My Audi S4 will be 10 years old in February next year, luckily it has a huge coolant header tank and what I plan to do is extract as much as I can from that tank, and backfill with 50/50 G13 or whatever is the current VW Group coolant version for these cars. Hopefully I can get 1.0>1.5 litres out each time, but I will not know until I've tried! Like the Polo and all other VW Group products, some coolant is flowed back into that header tank continuously, so after maybe 200 miles what I've added will have become fully mixed with the older coolant - a very dumb but simple way to add back in some corrosion resistance, ie take the coolant back from approaching acid towards alkaline. I have coolant "testing strips" made for the purpose of accessing both acidity and freezing point of these coolants, but I have not noticed much in the way of a change over the years both with my 2011 car, my wife's 2015 car or my daughter's old, previous late 2009 car, so two possible reasons, firstly, VW Group G12, G12+, G12++ and G13 work very well in these cooling systems, or secondly, these test strips are useless. I have also checked some sealed G12 conc and mixed 50/50 a few years ago and bought a new sealed container of G13 and mixed it 50/50 and checked both of them to give me a sort of point of reference for using these test strips and the movement "away" from the initial PH starting point of new G12 and G13 has been quite small. I suspect that the cooling system capacity in my S4 is 12 litres, so I repeat this removing>replacing coolant until I have removed and replaced a total of 12 litres, I will be happy for a few more years, or until I sell on my car.
It does seem that every aftermarket supplier of G12 etc and G13 place a tight and short service life on their products, but why if VW Group don't?

[wolfie]

It does seem that every aftermarket supplier of G12 etc and G13 place a tight and short service life on their products, but why if VW Group don't?

The cynic in me thinks the whole "service-life/use buy" of lots of products has more to do with stock cycles and profit margins than any reduction in performance. I would imagine the PH of the stuff sitting on a shelf would not move even over decades. Even once in the vehicle, after an initial time period the system should reach equilibrium and things should be stable. The switching out the fluid in the header tank seems a sensible approach, certainly less problematic than splitting hose joints and refilling.

I had a quick look at the vacuum refill adaptors a little while back when I was contemplating doing the timing chain. It seems pretty straight forwards and a clever way to do it. Only issue that put me off is that due to you placing the whole cooling system under vacuum it has a tendency to collapse all the rubber pipes. Thing is with the CBZB is that it has a big plastic pipe that comes off the water pump, runs across the back of the engine and into the thermostat housing. Plastic ages over time and being heat cycled. If that pipe should decide to split because it's being compressed, what was a little job becomes a pain in the rear end. Old cars have old parts and parts fail anyway. What with the rats nest of rubber pipes and plastic unions, pinching a bit out of the expansion tank and refilling with new fluid sounds the way to go, maintenance wise.