EGR Cleaning?

[Gerg]

On 6/11/2020 at 5:31 PM, Wooster said:

may not pass the next Mot emission test

It's not very widely known, but there is no emission test for hybrid cars in the UK, currently.  So this aspect of the test should not cause him any problems.

You are not alone in thinking that the Prius gen2 was outstandingly robust when compared to the car that followed it.  I think commercially, Toyota's innovative investment in hybrids meant that the new technology had to be seen as very reliable on the gen2, otherwise the conservative car buyers would be reluctant to adopt it.

From an engine point of view, gen2 vs gen3, some of the gen3 shortfalls can be accounted for through the adoption of newer engine designs which, while being more efficient and/or having lower friction, don't seem as durable than those in the Prius gen2. (e,g. low friction piston rings with poorer long term oil control.)

Also, as mentioned above, the newer model had to have better emissions performance than the old one (for the new Euro 5 standard), which from a nitrogen oxide (NO, NOx) perspective, meant the adoption of the EGR circuit that you see, to try to keep the combustion gases within preferred temperature limits - nitrogen is fairly unreactive at the lower temperatures, so it just stays as nitrogen!)

I think (I have yet to see this discussed) part of the problem with the hybrid and its EGR, is that the engine is often running at below what would be considered a 'normal' operating temperature, not least because of its 'stop - start' nature.  The combination of cool(er) temperatures, and columns of EGR gas moving, and then stopping and being allowed to cool inside the pipes, causes the vapours/particles in those gases to settle/condense onto the pipes and harden, eventually blocking them. Certainly carbon build up is more pronounced in any car engine that doesn't get thoroughly 'worked'. 

And at least the Toyota EGR cooler and valve don't actually break (failure of valve to open/shut or leak coolant!), as they do on many cars, especially diesels, even at surprisingly low age and mileages (VW, BMW etc.).

The gen4's new thermostatic radiator grille-blind will help keep that car's engine bay temperatures up, although this isn't its purpose, so maybe the gen4 has less susceptibility to the EGR problem for that reason as well, although this will be small.

As mentioned in Tony's post, on the gen4 the EGR collection point has moved from pre-cat (in yours) to post-cat, so now the gases in the circuit have been thoroughly cooked by the catalyst core before returning.  It would be interesting to know if this was mostly to address the problems in the gen3 EGR, or just to push down the tail pipe emissions still further.

From a development point of view, it is probably much easier to test an engine's durability at it's upper limit (that is to say; flogging it), than it is to thoroughly test an engine with a simulated 'run engine for 10 minutes, park for 6 hours, heavy traffic for 15 minutes etc., etc.', which is much more time-consuming, I would imagine.  But of course, both types of test are essential, the latter one just needs more ingenuity and patience, I would think.  Perhaps this is why this problem was not properly identified at the development stage?

I'm happy to be corrected on any of this, naturally.

[QuantumFireball]

40 minutes ago, Gerg said:

And at least the Toyota EGR cooler and valve don't actually break (failure of valve to open/shut or leak coolant!), as they do on many cars, especially diesels, even at surprisingly low age and mileages (VW, BMW etc.).

Also in relation to BMWs: At least the Toyota EGR systems don't catch fire :)

I'd also be interested to see if the Gen 4 EGRs are more reliable, I guess they're still mostly too new for us to really know.

[Gerg]

Exactly!  Early last year, weren't some BMW models banned from multi-storey car parks in China, on account of their tendency to catch fire when parked?

Not that it caught fire, but, my neighbour's low mileage, 2017 BMW 520d, has recently spent a month off the road (dealer initially quoted 3 months!) whilst it waited for a new EGR cooler to arrive - under warranty, of course.

Re: Prius gen4 vs gen 3, not much change to see from the outside of the EGR coolers, just chunkier, so a bigger radiator surface area? .  Gen3 on the right (that's 2nd one down, for you phone-using Jonnies). 

[QuantumFireball]

Not sure about elsewhere but there was a recall of affected BMWs in Ireland, and the dealers were impounding vehicles while they were waiting for replacement parts (some were waiting months).

[johalareewi]

So a plug in prius could have more egr issues than standard prius?

[Gerg]

7 hours ago, johalareewi said:

So a plug in prius could have more egr issues than standard prius?

An interesting question!  I would have expected the way the engine is used in the plug-in gen1 to make the EGR problem less likely or the same as the normal Prius, depending how much use you're making of its (rather limited) electric range.

But I don't know how the plug-in gen1 fits in with the warm up cycle description listed in this thread:-https://priuschat.com/threads/the-five-stages-of-prius-hybrid-operation.12919/  

The EGR carbon build-up is not something I've spent any time considering, but my idea seemed logical.  The EGR gases in the Prius are not different to any other petrol engine, why do they seem prone to sooting up the pipes? 

It would be good to hear other ideas....

[TonyHSD]

The design of the cooler and the entire system is the problem imo, and perhaps the Atkinson cycle. I’ve seen other petrol engines with simple egr without coolers and they look a bit cleaner. 

[Wooster]

Firstly I'd like to thank everyone for their comments.  It's been fascinating and educational.  Lots to pick up on but I'll limit myself to two entries:

1)  I removed the EGR pipe and cleaned it with oven cleaner.  (Thanks for the suggestion.)  I've inserted a pic of it before cleaning.  Does it tell you anything about the state of the rest of my EGR system?

2)  The maker of the EGR cooler is Denso.  I found this article about the Gen 3 EGR and you might find the comments (at the bottom of the page) from 'Herm' and 'Eschewo' interesting.  Just remember the comments were made in 2012:  greencarcongress.com/2012//denso

 

 

[FROSTYBALLS]

The article is related to the Prius C - a supermini sized hatchback and what was the US equivalent to the European Yaris Hybrid - so the EGR may not be the same as fitted to the larger Prius.

[johalareewi]

7 hours ago, Gerg said:

But I don't know how the plug-in gen1 fits in with the warm up cycle...

On my gen1 PIP in EV mode it starts off in S0 then when the ICE kicks in it goes to S1A (with the ICE doing about 1500 rpm) then S1B. Once S2 is reached it turns off the ICE and goes back to EV operation (unless the ICE is still required).

While EV running in S2, the ICE cools and if it has got too cool when needed again, stage S1B will be repeated.

The key thing is the PIP can go down the start up cycle if the ICE cools too much when running in EV.  Could this prolong the time that the EGR is on recycle instead of exhaust and cause more build up?

[Gerg]

16 hours ago, johalareewi said:

Could this prolong the time that the EGR is on recycle instead of exhaust and cause more build up?

I don't think the EGR function sees any use at all until the engine is up to normal, (73 C+) temperature, so this shouldn't complicate matters at all for your car.

I seem to remember that I read (on another forum) that Toyota went through several (3?) different part numbers of head gasket up until 2013.  I have no idea why this might be, but I would guess that the newer designs were to make them more durable, perhaps someone on here knows?  So yours will be the later (better, hopefully!) design.

18 hours ago, Wooster said:

Does it tell you anything about the state of the rest of my EGR system?

I have yet to take the EGR circuit apart on our car as the mileage is a little on the low side for that (72,000 miles, mostly brisk!), but I might have a look in the next month or so.  Your picture shows significantly less carbon build up than the photos that I have seen, but those pictures are usually of bad-running examples on Priuschat, so you've likely seen them as well.  Like this one, taken from the thread of Dan Latu's epic, complete, and extremely thorough, engine strip down (at 150,000miles?, I cant remember exactly).

I have a cheap eBay endoscope, which I might try to put to good use on this.

18 hours ago, Wooster said:

The maker of the EGR cooler is Denso

On the Prius gen3/Auris, the cooler is this brand:-

So, certainly not badged Denso on these cars, unless this company is a subsidiary.  This isn't my picture, this is an eBay UK one, but I have a spare one of these, (to swap in, when it eventually needs cleaning) and it is exactly the same as this one in every respect.  An interesting article - you've done some serious reading on this!

HTH

 

[QuantumFireball]

On 6/21/2020 at 9:07 AM, Gerg said:

An interesting question!  I would have expected the way the engine is used in the plug-in gen1 to make the EGR problem less likely or the same as the normal Prius, depending how much use you're making of its (rather limited) electric range.

But I don't know how the plug-in gen1 fits in with the warm up cycle description listed in this thread:-https://priuschat.com/threads/the-five-stages-of-prius-hybrid-operation.12919/ 

The stages are the same, though one difference is the ICE could be starting from cold at any speed up to 85 km/h, though significant power output from the ICE is restricted until it's in one of the later stages (or you really floor it). Not sure how that affects EGR usage.

On 6/21/2020 at 9:07 AM, Gerg said:

The EGR carbon build-up is not something I've spent any time considering, but my idea seemed logical.  The EGR gases in the Prius are not different to any other petrol engine, why do they seem prone to sooting up the pipes?

Could it be related to the known flaws with the piston rings? These engines are known to consume oil with high mileage, and I would guess that burnt oil is getting into the EGR system?

I also wonder if there's something about driving conditions in the US that are making these issues more prevalent? EGR issues and head gasket failures seem more common there. One thing is that petrol is a lower octane there, typically around 91 RON for "regular" - this could mean different pressure, exhaust temperature, etc. Of course there are different environmental conditions too. Or maybe it's just the fact that they typically drive longer distances than in Europe, and the Prius is a more popular car there...

[Gerg]

1 hour ago, QuantumFireball said:

Could it be related to the known flaws with the piston rings? These engines are known to consume oil with high mileage, and I would guess that burnt oil is getting into the EGR system?

Yes, I would agree with you.  Perhaps a way to put that to the test might be to check an an engine that has not started burning oil, and see if the EGR carbon build up is proportionately (by mileage) less, or even barely existent at all.  

My spare EGR cooler allegedly came off a written-off Prius with 55,000 miles from a small, local breaker's yard, and it was a long way from blocking up, but it wasn't that clean either.  I might have a picture of it somewhere, taken before I cleaned it.  But the car breaker was able to quote the mileage of the car so quickly, you might question the accuracy of that mileage figure!

On a bit of a whim, I have just contacted Shell UK technical department (now in Singapore, actually) about the use of V-power fuel, to see their opinions on it cleaning piston rings, especially oil control rings (they say they wouldn't expect it to, it's too far away from the combustion area), and also,  if engine oil burned in an engine suffering poor oil control would be any less likely to produce soot if was using synthetic oil (over mineral or semi-synthetic), they wouldn't expect to see any difference in that, either. 

I also asked if using their V-power fuel would have any beneficial effect on EGR cleanliness at all, in a modern petrol engine, they said it would not help.

The answers were what I was expecting, I was just interested to see the Shell official view on this.  The chap was very friendly and patient with his answers, he was in no rush to 'get me off the line'. 

There were one or two questions he was a little hesitant on (but there was some time-lag on the line anyway) - he suggested I might like to try emailing - productinfo-uk@shell.com, I think this may have been because of his potentially overstepping the mark in some answers.  He would not be drawn on answering model-specific queries, as he said that it was not for Shell to comment on other company's designs. 

[TonyHSD]

Hi everyone, 

I like to add that the oil burners are very often poorly maintained cars with low mileage and they do so due to the stuck piston rings where the high mileage  cars may start little use of oil due to the wear and tear of the engine components. Any gen 3 Prius or Auris older than 8 years or 80k miles would benefit of cleaning procedure as include throttle body and intake manifold cleaning, this soothes that you see inside the pipe also accumulates inside the manifold and restrict the air flows from the egr into the combustion chamber via tiny holes build onto the intake main air channels, those needs to be cleaned too. I am adding following pictures of my cooler at 136k miles, the pipe is only at 36k miles because I did cleaned at 100k. It might looks ok on pics but it took me two days and cleaning using jet wash, metal spoke, egr cleaner spray similar to oven cleaner. 
Regards 

[Wooster]

Again, a fascinating selection of views, thought and knowledge.

For reference, my EGR pipe was at 80k miles and the engine is not using any oil at all:

 

TonyHSD - you could start offering an EGR cleaning service to TOC members!

The Workshop Controller at a Toyota main agent confirmed the Gen2 was 'over engineered' and that Toyota made little profit from making it.  The Gen 3 was less expensive to produce.

The same Workshop Controller told me the EGR on the Gen3 was modified (because of soot issues) at the time the car was given a facelift in 2012/13.

Interesting as this is, we must remember there are thousands of Gen3s out there that have well over 100k under their wheels with no faults or error codes!

 

 

[QuantumFireball]

I didn't realise the EGR system changed with the facelift, mine is a Plug-in so post-facelift but it's only done about 76k miles so far so I haven't taken a look inside yet. I also use Dipetane, an additive that's supposed to help reduce carbon build-up but I honestly have no idea if it works. I'm planning on checking out the EGR once it gets to 100k, might be a few more years at this rate :)

[Wooster]

I contacted my (so far, trustworthy) Toyota main agent and asked the Workshop Controller for a quote on cleaning the EGR system.  He replied with £400+ for cleaning the EGR valve and intake manifold.  I asked him if he they also cleaned the EGR cooler.  His reply was:  (Copy & paste)  "No we do not remove the cooler as it rarely has issues with blocking, although we do as part of this procedure remove the spark plugs and blow back thorough the cooler , which then blows any carbon deposits back through the cylinders and out of the spark plug holes."

Your comments would be appreciated!

[TonyHSD]

Hi, that’s interesting new thing to learn. I am not sure how much they can remove with Air blow , this soothes is rock solid not a dirt., and also blowing anything through cylinders maybe a dangerous if any deposits left free on top of the pistons., I am not aware of any procedure like that. Last time I spoke with Toyota service team, the guy at the desk said to me to get everything off the car, check and thoroughly clean, as I did. There were two gen 3 Prius in the yard with bonnets up and people working on same thing. £400 for not taking cooler out and properly clean it doesn’t seems a good offer to me. There are some jobs on cars including this one that are best suited as DIY projects because of the intense labour involved and many hours,  I understood many people has no knowledge or equipment to do themselves. There are some small garages that offer that kind of services, I personally can not recommend any as I usually like to do the work myself and where not possible may ask a specialist garage or Toyota main dealer which seems expensive solution. Thanks for the idea offering service to members, I thought before but never actually materialise,  maybe just offering a free advice over the forum it’s just fine. All the above procedure parts cost around £60, mainly cleaning sprays and 4-5 gaskets if properly done, egr gaskets can be skipped at first opening but intake manifold Must be changed. , 2L Ready mixed coolant, and the rest is all labour. Maybe just clean the pipe, throttle body and manifold under the body where you will find oil. Enjoy your car till reach 100k or start hearing that nasty knocks and then do the procedure together with new all coolant for the engine. 👍