EGR cooler cleaning-Prius V 2016

Am I reading that correctly, 270000 km, about 168000 miles for us in the US?

Nice job.

Did you happen to record the car's EGR flow test results before the work, or after the work, or both?

 

Hi Garry,

There's nothing wrong with those sorts of qualitative reports, but we also have a thread where we're making the effort to collect quantitative information that will be of help to others in estimating the benefits of the work for their own situations.

If you didn't happen to note your EGR flow test value before the work, there is still an opportunity to add your test value from after the work. That contributes to our having a good idea what values to expect from a recently cleaned system.

 

Good job. That is exactly the same tool combination I used. I also took a picture of it to remember it next time.

 

For the cooler nut on the underside bracket? Some just remove it and leave it off. I also backed out the stud, left it off. You can do this anytime. The stud was tough to get off, just poor access and it had a lot of resistance, so much I was worried I would strip the head.

 

I left that stud in place, seeing no need to fuss with anything poorly accessible and tough with a lot of resistance.

Of course that meant I needed the two studs out of the aft end of the cooler, but they were comparatively accessible and didn't give me any trouble. And having the lower stud in place gave me a convenient place to hang the cooler while lining the other holes up to reinstall it.

 

Doesn't 2016 Prius V are using latest Gen3 engine with Piston rings improved. EGR valve shouldn't be that bad. Can't wait to see you EGR cooler photo.

 

I was planning on the same EGR cooler clean but now think I should go ahead and do the head gasket replacent at the same time. What does that do to the process of getting to those difficult bolts? Haven't looked too closely yet and wondering if that can be done differently since I will be removing the whole head. Any guidance appreciated.

SM-G781U ?

 

I left my stud in place because It served as a support point to hold the EGR when I was reinstalling it. I also did leave out the nut though like you are saying.

 

Given that:
1) a plugged EGR system would be putting LESS exhaust gas into the Intake Manifold,
2) A Cleaned EGR system would be putting MORE exhaust gas into the Intake Manifold,

I would not expect a noticeable difference in performance or mileage after unplugging the EGR system. In theory, the car might get better performance with a plugged EGR cooler, (at least until bad things happen). The reason the EGR is so important is that it keeps the combustion temperature down. This prevents a blown head gasket or burning a hole in the piston. Really bad is when enough coolant floods a cylinder, a connecting rod breaks, and a hole get blown through the side of the engine (not a joke).

I may have to redo EGR cooler soon, and I like a fool put the nut back on the lower bolt. In the process, I lost an a 3 inch extender and a 1/2 inch socket to the tool gods in the bowels of my engine. That tool you show looks like the right one for the job

The "EGR FLOW INSUFICIENCY" is a value stored in the computer as the result of testing the EGR system (if the test fails, a very low number will be stored). You need an ODBII tool to read it. Several Android phone apps and a $25 ODBII adapter can read this value. It is a really nice to see that number go up after you go through all the work of cleaning.

 

Normally, you have to lay on top of the engine and reach down behind to get to the nuts.

Getting to the nuts and studs attaching the EGR cooler to the exhaust will definitely be easier with the head removed.



Posted via the PriusChat mobile app.

 

To describe it like that is to kind of completely ignore the engineering reasons why EGR is used on a gasoline engine in the first place, and think only about things that might go wrong when an engine designed for it isn't getting it.

It is put there in the first place to allow pushing the engine parameters to levels of efficiency that otherwise wouldn't be achievable without either knocking or producing too much NOx. As a kind of free bonus, it also allows running the engine at lower power with a wider throttle opening, which reduces the energy lost sucking across the throttle plate.

It's funny reading what people sometimes write about EGR, as though the whole idea of including exhaust in the intake charge somehow is triggering an insular-cortex disgust reaction that gets in the way of thinking about it. Like, it just makes some people think of a person eating poo, instead of applied chemistry.

Maybe it's easier to think about towing a trailer that has a big tank of a fuelless, oxygenless gas that won't burn. There are good things you can do with a gasoline engine if you have a nice gas that won't burn you can mix in with your intake charge. It doesn't mess up the fuel/air ratio, making the mixture too lean or too rich. The mixture stays Just Right, only with a bit more distance between the fuel and oxygen molecules, stretches out the burning process in the cylinder, makes the temperature and pressure curves less steep, reduces your emissions, lets you throttle the engine less, and lets you use levels of timing advance and so on that you couldn't otherwise get away with. It's a pretty decent collection of benefits.

Now, it wouldn't net you very much efficiency if you really needed to tow around a big tank of unburnable gas, and fill it up somewhere twice a month. But the good news is you don't really, because there's a pretty reliable supply of cheap unburnable gas everywhere your engine goes already.

That's why they build the things with EGR. I'm not surprised at all if the car runs more smoothly and more efficiently with the system working as designed.

It's not like they put it there to avoid blowing up your gaskets or your pistons. Cars without EGR were made for decades that didn't blow up their gaskets or pistons.

But then, an engine that's designed to have EGR may be designed to push its timing and so on to levels that could cause knocking and its resulting damage if the intended EGR isn't really happening. That's why the ECM monitors the system, and falls back to fail-safe, less-efficient parameters if it detects the EGR isn't flowing adequately.

One fly in that ointment, though, is the passages in the manifold itself. The ECM's monitor test can't tell when some of those passages are more clogged than others, so it might think things are ok, while some cylinders are getting more EGR and at risk of misfiring, and others are getting less and at risk of knock.

 

Yeah, I took some liberties to grossly over simplify EGR. That is unusual for me, as I tend to overthink things (it is in my signature after all). I was just trying to set up expectations that a big boost in performance or efficiency is not what to expect when unplugging the EGR system. The main reason to do it is to prevent engine damage.

Remember the original purpose of EGR was for emissions. EGR would cool the combustion peak temperature so there would be less Nitrogen Oxide out the tailpipe. Also the air sucked in is 80% unused nitrogen, so Nitrogen Oxides are easy to create..

Good point to emphasize in your last paragraph. The EGR test can't tell if one cylinder is getting less exhaust gas due to a clog in one passage. If one cylinder gets less exhaust gas because of a blocked IM passage, that cylinder will be the one to blow its head gasket before the EGR monitor can detect a problem.

 

That's easy to remember, but sometimes makes it too easy to forget that for gasoline engines there's more to the story.

The increases in MPG possible in a gasoline engine with EGR through such effects as reduction of throttling losses are good parts to remember also.

Some of those benefits don't apply to diesels. For example, diesels don't use throttles, so the throttling loss reduction isn't a thing for them. Diesel drivers used to kind of be right when they said "this EGR is only here for emissions, doesn't do me any other good." And in the diesel universe there have been "EGR delete" kits for the folks who didn't care about the emissions. But gasoline engine drivers who copy that are forgetting that there's more to the story for them.

I think I've recently seen some info that even diesel engineering has been finding ways to optimize for EGR use, given that they need it for emissions anyway, and so more recently it might not be quite true to say "doesn't do me any other good" even about diesels. A diesel owner who does an "EGR delete" on his next truck because it's what he did on his last truck might be stuck a little behind the times.

 

Get the head gasket done now and you'll save yourself a lot of trouble later if you plan on keeping the car past 300,000.

 

I was just about to give up when I got to those two bolts in the back but then I found this post. I used some foam to lay across and I was able to get em off! Thank you so much

 

Remove and leave off both the nut and the stud at the lower EGR cooler bracket, and then you can leave the rear two studs on the cooler. Next time. And you miss the "fun" of getting that lower bracket nut off.

Torque values for all in a pdf attached in first link in my signature.

 

Oh wow! Thanks for info…that lower nut was a pain