Does using Coasting Function clog the EGR?

[Dill Tart]

67 plate 204 4Motion, 57,000 miles. We have had the usual EML appear in the past, even on long continental trips, we fill up every 2-3 tanks with the higher grade diesel to minimise problems.
After 3 EGR flushes by VW and new improved pipework fitted the light appeared after a few months, fault cleared, and again, fault cleared and……..again!
We then went to an independent VW specialist who recommended biting the bullet and fitting a new ‘improved’ EGR. After 9 months, you’ve guessed it, our friend the EML was back on the fault cleared 2-3 times and then today after less than 10,000 miles since the new EGR fitted the independent VW garage diagnosed a blocked EGR valve & pipe.
We do mainly long journeys very few short runs but do use the coasting function all the time for MPG reasons, would long periods on tick over cause this? Any advice or thoughts helpful.

 

[dspuk]

How does coasting (assume you mean ACC) mean long periods on tick over? The engine is running at the same speed as with your foot on the pedal.

Edit - the "coast" feature is new to me so will investigate (before you all flame me...)

 

[colintfcolintf]

If it’s a T6 DSG then if you lift off going down hill for example it will coast along but engine speed is at tickover

 

[Dill Tart]

Yes it’s the T6 DSG, the engine goes to tick over unless you touch the brake or accelerator.
Just back from the VW independent garage, £162.00 to carry out test, remove EGR pipes and put a camera into the EGR valve, completely blocked. Booked in to have the EGR valve removed, cleaned and refitted, it’s getting expensive, £1,235.94 August 2023 for a new EGR valve, £162.00 today and another at least £500 due soon!

 

[Mansfieldman750]

Same on T6.1. When you are in Coast the gear indicator changes from D7 to D and an eco symbol appears.
I’m probably throwing away the money saved by Coast but every now and then I put it into M5 in manual which from memory is about 4000 revs in 5th and leave it there for a few miles. In my way of thinking I’m giving it a clean out.
70mph in D7 is just under 2000 rpm and it just leaves me with a feeling that the engine is never really working hard. Shame there is no longer a sports mode.
I also run it on premium diesel whenever available which again might be thrown away money but each to their own, it’s my way of thinking I’m “ looking after “ the van.

 

[dspuk]

Same on T6.1. When you are in Coast the gear indicator changes from D7 to D and an eco symbol appears.
I’m probably throwing away the money saved by Coast but every now and then I put it into M5 in manual which from memory is about 4000 revs in 5th and leave it there for a few miles. In my way of thinking I’m giving it a clean out.
70mph in D7 is just under 2000 rpm and it just leaves me with a feeling that the engine is never really working hard. Shame there is no longer a sports mode.
I also run it on premium diesel whenever available which again might be thrown away money but each to their own, it’s my way of thinking I’m “ looking after “ the van.

Never noticed such a thing! I'll have a play next time I'm driving.

 

[Mansfieldman750]

Never noticed such a thing! I'll have a play next time I'm driving.

Does it every time on mine when I take my foot off the pedal going downhill.

 

[Jon A]

It's an interesting question about using coasting function and EGR

I have a 69 plate/5 yrs old with 43k. Always used for long journeys, never short.
Just had to have a new EGR fitted as it was leaking coolant into the engine. Fortunately caught inside the extended warranty period, which is now over.
From what I've read, a new EGR at this type of age /mileage isn't uncommon. I'm just surprised it had happened on a van that's only ever used for long journeys.

I'm also interested to learn if turning off coasting function and/or deliberately revving the engine will extend EGR lifespan .. Or maybe we just have to suck it up as a consumable item on these vehicles?!

 

[willwander]

Not had bother with coast on mine, I’ve always just driven mine normally and let Regens do their thing.

 

[andyinluton]

I think its what you do when its not coasting that maters, its very easy to bimble around without going over 1500 rpm for long periods.

I'd be interested to see if its those with the fantastic mpg figures that suffer more with clogged EGRs @Dill Tart are your long journeys foot down outside lane of the motorway or 50mph on A roads?

 

[Jon A]

I think its what you do when its not coasting that maters, its very easy to bimble around without going over 1500 rpm for long periods.

I'd be interested to see if its those with the fantastic mpg figures that suffer more with clogged EGRs @Dill Tart are your long journeys foot down outside lane of the motorway or 50mph on A roads?

I'm the outside lane type, and mine died. Albeit failed thru the internal exhaust gas/water barrier failing , rather than it becoming clogged.
So perhaps you can melt it by driving hard, or clog it by driving slow !!

 

[Meoncoast]

Our just sold late 2016T6 daily 96K used all the time no issues with EGR.

 

[TripleBee]

It's an interesting question about using coasting function and EGR

I have a 69 plate/5 yrs old with 43k. Always used for long journeys, never short.
Just had to have a new EGR fitted as it was leaking coolant into the engine. Fortunately caught inside the extended warranty period, which is now over.
From what I've read, a new EGR at this type of age /mileage isn't uncommon. I'm just surprised it had happened on a van that's only ever used for long journeys.

I'm also interested to learn if turning off coasting function and/or deliberately revving the engine will extend EGR lifespan .. Or maybe we just have to suck it up as a consumable item on these vehicles?!

I'm sorry, but I don't think a new EGR every 43k mi or 70k km is normal.
I replaced mine (T5.1, 140hp, so an easy one to replace) on a camping in the Dordogne at 45000km. But that was because of a faulty EGR from factory (there was a TPI that stated that one was faulty from factory). Since then, I have only covered 160000km (approx. 100000mi) with that second EGR.
I use the van as a daily (6000km/year) and for holidays (9000km/year). A lot of cold trips from and to work. On holidays, the rpm doesn't surpass 1900rpm for hundreds of km on the highways. I always buy the cheapest diesel (Super U, Intermarché, ...).
There are a lot of factors that can help clogging the EGR.
Normally the latest engines will capture the exhaust gasses AFTER the DPF, meaning there is no soot anymore to take back into the inlet.
The older engines unluckily capture the EG BEFORE they go into the DPG, meaning all the soot is returned to the inlet.

 

[KevH]

I'm sorry, but I don't think a new EGR every 43k mi or 70k km is normal.
I replaced mine (T5.1, 140hp, so an easy one to replace) on a camping in the Dordogne at 45000km. But that was because of a faulty EGR from factory (there was a TPI that stated that one was faulty from factory). Since then, I have only covered 160000km (approx. 100000mi) with that second EGR.
I use the van as a daily (6000km/year) and for holidays (9000km/year). A lot of cold trips from and to work. On holidays, the rpm doesn't surpass 1900rpm for hundreds of km on the highways. I always buy the cheapest diesel (Super U, Intermarché, ...).
There are a lot of factors that can help clogging the EGR.
Normally the latest engines will capture the exhaust gasses AFTER the DPF, meaning there is no soot anymore to take back into the inlet.
The older engines unluckily capture the EG BEFORE they go into the DPG, meaning all the soot is returned to the inlet.

Very interesting.
Could you define ‘latest’ and ‘older’ engines?

 

[temporarysecretary]

It's an interesting question about using coasting function and EGR

I have a 69 plate/5 yrs old with 43k. Always used for long journeys, never short.
Just had to have a new EGR fitted as it was leaking coolant into the engine. Fortunately caught inside the extended warranty period, which is now over.
From what I've read, a new EGR at this type of age /mileage isn't uncommon. I'm just surprised it had happened on a van that's only ever used for long journeys.

I'm also interested to learn if turning off coasting function and/or deliberately revving the engine will extend EGR lifespan .. Or maybe we just have to suck it up as a consumable item on these vehicles?!

What made you spot the issue?

Falling coolant level or something else?

 

[Jon A]

What made you spot the issue?

Falling coolant level or something else?

Yes, the coolant dropped. Caught it fairly quickly

 

[kurienp]

67 plate 204 4Motion, 57,000 miles. We have had the usual EML appear in the past, even on long continental trips, we fill up every 2-3 tanks with the higher grade diesel to minimise problems.
After 3 EGR flushes by VW and new improved pipework fitted the light appeared after a few months, fault cleared, and again, fault cleared and……..again!
We then went to an independent VW specialist who recommended biting the bullet and fitting a new ‘improved’ EGR. After 9 months, you’ve guessed it, our friend the EML was back on the fault cleared 2-3 times and then today after less than 10,000 miles since the new EGR fitted the independent VW garage diagnosed a blocked EGR valve & pipe.
We do mainly long journeys very few short runs but do use the coasting function all the time for MPG reasons, would long periods on tick over cause this? Any advice or thoughts helpful.

Similar miles, similar conditions, full EGR replaced - including pipe, valve and whatever else comes with it.

Nothing to do with coasting. I have switched off coasting though as it is a weired feeling when coasting and then you need some power. Better when there is engine power all the time. Not sure how much fuel it saves.

Now, for EGR clogging. Does your van consume ooil between oil changes? even a little?

This is my theory for clogged EGRs. EGR is exhaust gas recirculation. Exhaust gases from combustion being recirculated to increase CO2 in the combustion mix and thus reducing the overall temperature of combusion, and thus reducing NOX.

Now, if your van consumes even a little oil between services, where do you think this oil is going? it is going into the cylinders for sure. Not all of it is being combusted for sure. and some of it is being recirculated as well. It is this oil that contributes to the clogging.

All EGRs will get clogged at some time, but oil contributes to it happening sooner.

For me, I am just treating it as a consumable and a replacement EGR at 60,000 mls and the next one at about 120,000 mls, is reasonable maintenance. Nothing alarming.

Yes, even I would prefer that things don't break down. But physics also dictates that they do.

 

[TripleBee]

Very interesting.
Could you define ‘latest’ and ‘older’ engines?

Older engines will be starting with the letter C. Mine is a CCHA. (all up to 2020)
Latest engines are starting with the letter D. DNAA, DMZA. (starting in 2020)