Buzzing noise after engine stop

[rondeo]

Having often heard a buzzing noise from my MC tdci on engine stop, and having recently turbo problems I did a bit of searching and found what seems to be the cause of the buzzing at least. It seems to be quite common. The turbo boost is controlled by a vacuum modulator driven by PWM from PCM. The buzzing comes from that valve. Anyone else wondering what this buzzing might be, take a look at this:

www.pierburg-service.de/ximages/pg_si_0076_en_web.pdf

[ope126]

The link doesn't work, can you try again.
I would be interested to hear / read about this issue also!

[rondeo]

http://www.partinfo.co.uk/docs/178

[ope126]

That's better...

[rondeo]

There's some interesting reading on the

http://www.partinfo.co.uk/

site in general. Pierburg also make the vacuum pump on MC Mondeo.

[rondeo]

And a slightly to my mind confused account:

https://youtu.be/LvotSKD0pHw

[Mondaveo]

That's interesting.

I've noticed that my MC TDCi sometimes makes a noise several seconds after the ignition is turned off - even well after I've gotten out and locked up - it's not a buzzing, but sounds somewhat like someone operating a foot pump. It goes about half a dozen times (out-in "breaths") and sounds a little like it could be moving fluid. Something in the hydraulics I guess? Was spooky the first few times I heard it!

[Peter B - CV8]

Not sure about Mondeo's - but a lot of vehicles do a "Mass Air Flow burn off" once the engine is switched off. The MAF sensor wire is heated up to burn off any contaminants.

[Binny]

Originally Posted by Mondaveo

That's interesting.

I've noticed that my MC TDCi sometimes makes a noise several seconds after the ignition is turned off - even well after I've gotten out and locked up - it's not a buzzing, but sounds somewhat like someone operating a foot pump. It goes about half a dozen times (out-in "breaths") and sounds a little like it could be moving fluid. Something in the hydraulics I guess? Was spooky the first few times I heard it!

I think I know what you mean. It sounds like some solenoids cycling a few times or something like that. Click clunk click clunk click clunk after shut down.

[cyclone1410]

Originally Posted by Mondaveo

That's interesting.

I've noticed that my MC TDCi sometimes makes a noise several seconds after the ignition is turned off - even well after I've gotten out and locked up - it's not a buzzing, but sounds somewhat like someone operating a foot pump. It goes about half a dozen times (out-in "breaths") and sounds a little like it could be moving fluid. Something in the hydraulics I guess? Was spooky the first few times I heard it!

My Ecoboost does a similar thing. When I am sitting in the car parked, it starts about 5 minutes after switch off. Is totally normal by the way but does sound like it is possessed.

[rondeo]

Originally Posted by Mondaveo

That's interesting.

I've noticed that my MC TDCi sometimes makes a noise several seconds after the ignition is turned off - even well after I've gotten out and locked up - it's not a buzzing, but sounds somewhat like someone operating a foot pump. It goes about half a dozen times (out-in "breaths") and sounds a little like it could be moving fluid. Something in the hydraulics I guess? Was spooky the first few times I heard it!

That's the egr valve opening and closing for the purpose of cleaning.
It varies from three times and up.

The buzzing is a different noise which occurs immediately on switch off.
It's the turbo vacuum control valve. Cars with pneumatically operated egrs (maybe prior to 2009?) have two of these valves, one for egr and one for turbo. Not all cars do it but it's fairly common and is the subject of youtube videos. One of our two Mondeos nearly always does it, and has done for the last few years without apparent problem. I'm fitting a new valve in it tomorrow, as it's got a turbo issue, not because of the noise.

[Mondaveo]

Originally Posted by Wikipedia

In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders.

Mystery solved! Thanks for that info.
Going to listen closely next time and see if i can hear the turbo vacuum control valve too.

[Binny]

With reference to the original link, you can just copy and paste it into your browser.
Thats an interesting doc. So they are saying that if the rubber hose goes stiff from age and heat it can cause this. Whereas a nice new supple rubber will expand with the hammering and absorb it.

Had a sort of similar issue with a fuel hose on my old Cordia turbo once. It split while I was driving along and showered the hot engine bay in fuel. That was a puckering moment! When I replaced it I had pirtek make a replacement and it was made from hose that could handle 2000PSI. It was that stiff the large single point injectors were causing a hammering through the pipe back to the steel pipe which was vibrating against the firewall. Doh.

[rondeo]

You won't have to listen very hard, the buzzing is quite loud, the clunking is pretty quiet. Not all cars do the buzzing, evidently, and it's not clear from the Googling and Guessing if it's a sign of malfunction or not.

[Mondaveo]

So it turns out my car buzzes too. A short low 'mzzzrt' as the engine shuts off. Have heard it a couple times from outside the car, never noticed it from the driver's seat.

[rondeo]

My car did the buzzing for three years and had no obvious mechanical issues until recently a P2263 and limp mode, which happened twice two months apart. Have replaced the valve and the buzz has gone, for the moment at least. Hopefully that will keep the turbo system happy. Wait and see.

[juzandbec]

Sorry if this is old news now but my understanding (read on a forum) of the clicking noise (click clack 6 times ) is the powershift transmission performing a cycling or reset of the gears.
I always wait to hear it now, count the 6 clicks for each gear and find it comforting that all is working in the powershift.
I also have the buzzing noise - for quite a while after I bought the car I thought it was a receding prop aeroplane until I parked in an underground car park and realised it was my car ��

[rondeo]

Originally Posted by juzandbec

my understanding (read on a forum) of the clicking noise (click clack 6 times ) is the powershift transmission performing a cycling or reset of the gears.

The clunking sounds after switch off are made by the egr valve. Definitely not the transmission.

From the Ford workshop manual:

'At the end of each drive cycle the PCM drives the EGR valve to the fully open and fully closed positions several times. This assists with cleaning the EGR valve.'

The actual number of clunks is variable from 3 to more than 6, decided by PCM. Usually starts a few seconds after switch off.

[rondeo]

Just for further interest, paraphrasing the Ford manual on egr clacking:

The PCM decides whether to keep cycling the egr valve based on the the output of a position sensor (yes, another one). If the sensor indicates the valve has not fully closed the clacking continues to a maximum of 18 times. If this fails a DTC will be set and the valve should be replaced.

[juzandbec]

I beg to differ rondeo. From a letter released by Ford titled 'PowerShift 6 Speed Operating Characteristics' - Point 3 under section 'Common Characteristics of the PowerShift Transmission: Common Sounds a driver may notice are:

• Clicking sounds after the engine is turned off. As the vehicle is powered down, the transmission will cycle the clutches to the released position so it is ready for a safe restart of the engine. This is part of normal operation. Clicking sounds from the transmission immediately after the engine is turned off are normal.

I'd say this sounds exactly like the noises I hear and there are always exactly 6 of them.

Just my experience.

[Mondaveo]

Originally Posted by juzandbec

From a letter released by Ford titled 'PowerShift 6 Speed Operating Characteristics'

Is this the letter?
http://www.fordfiesta-club.com/Club/...a.ua-2dps6.pdf

What a strange publication. They sent this to Fiesta and Focus owners in the US?

Originally Posted by juzandbec

• Clicking sounds after the engine is turned off. As the vehicle is powered down, the transmission will cycle the clutches to the released position so it is ready for a safe restart of the engine.

I'd say this sounds exactly like the noises I hear and there are always exactly 6 of them.

That passage says it's cycling the two clutches, not the six gears. Cycling through the gears after engine shutoff makes little sense, anyway. If it needs to check the shifters work, do it at startup before you start driving anywhere?

But who knows for sure, eh?

[rondeo]

The letter applies to Focus and Fiesta which have dry clutches?
Different powershift transmission?

https://en.wikipedia.org/wiki/Ford_P...t_transmission


Electric solenoids control hydraulic actuators which move the shift forks.
There's no hydraulic pressure when the engine's off, so not possible to move anything anyway.

[Mondaveo]

This was my Google search:
https://www.google.com.au/search?q=P...haracteristics

All the hits seem to be Focus and Fiesta. The Wards news article that comes up only mentions Focus and Fiesta. One forum poster even remarks Ford should've used the Fusion's Powershift!

[rondeo]

Originally Posted by rondeo

Electric solenoids control hydraulic actuators which move the shift forks.
There's no hydraulic pressure when the engine's off, so not possible to move anything anyway.

The Focus and Fiesta dry clutch powershift transmissions are Getrag 6DCT250 while the Mondeo wet clutch units are 6DCT450. The 6DCT250 uses all electric actuation. The 6DTC450 uses hydraulic pressure controlled by electric solenoids. The 6DCT450 can be locked manually with the stick.

There were problems with the 6DCT250. I suspect that's partly why powershift has a bad reputation.

[ope126]

Extract from Promotional Material before the launch of the MC Mondeo (Ford of Europe)

Ford PowerShift: Easy and Efficient

Ford PowerShift (6DCT450) is standard equipment on new Mondeo with either the 203 or 240 PS 2.0-litre EcoBoost engine – creating an advanced combination that delivers new levels of fuel efficiency and low CO2, yet still demonstrates that driving pleasure does not need to result in high CO2 emission levels. Ford PowerShift is also optional with 140 and 163 PS versions of the 2.0-litre Duratorq TDCi common rail turbo-diesel engine.
Developed by Getrag Ford Transmissions GmbH as a 50:50 Ford and GETRAG joint venture, the Ford Powershift transmission consists of two layshaft transmissions working in parallel, each with its own wet-clutch unit.
Thanks to the layout of the intermediate shafts – one carrying the 'uneven' gears 1, 3 and 5, and the other the 'even' gears 2, 4 and 6 – subsequent gear changes can be prepared by pre-selecting the next gear while in motion and at full power. The change then takes place through the opposed activation of both clutches, this being co-ordinated to avoid torque interruption.
In contrast to conventional automatic transmissions, the basic technical configuration of the Ford PowerShift transmission offers numerous advantages. It does not, for instance, require any complex sub-systems such as torque converters, planetary gear sets, multiple wet-clutches and multiple bands – all of which significantly reduce gearbox efficiency through increased inertia and drag torque effects.

Homologated fuel economy data for the 203 and 240 PS 2.0-litre Ford EcoBoost engines paired with Ford PowerShift, clearly demonstrates how efficient a modern powertrain combination with automatic transmission can be. The new Mondeo with this state-of-the-art powertrain delivers a combined fuel economy of just 7.7 l/100 km (36.6 mpg)* and an average CO2 emission level of just 179 g/km. The combination of Duratorq TDCi engine (140 or 163 PS) and Ford Powershift, generates an even more impressive combined fuel economy of just 5.6 l/100 km (50.4 mpg)*, with an average CO2 emission level of just 149 g/km.

For the driver, using Ford PowerShift is as simple and easy as a conventional automatic transmission, with a standard automatic gear lever in the centre console and the usual P, R, N and D settings available. In addition to this regular set-up, sport and manual modes can be selected by moving the gear lever to the right and into another adjacent position. In sport mode the transmission adjusts the shifting points to a higher revs for more performance, and down-shifts are executed more instantaneously if harder acceleration is required.