Techstream EGR Valve Blockage Data

Wow, had not considered the impact of altitude! That's a big deal where I live, higher than "high altitude cooking" levels

Here's a good calculator: Air Pressure at Altitude Calculator
And the details behind it: Atmospheric Pressure vs. Elevation above Sea Level

It looks like EGR pressure is a *relative* value, since normal sea level air pressure is 101 kPa at 59F. So I have no idea if I should expect a change at altitude or not.
The answer above about kPa "difference between 1000' and 3000' is around 7kPa" needs the context: that's given 101 kPa at sea level

IF altitude EGR values do change, then at 7000 feet, I guess I should expect 78% of sea level, so 15.6 kPa instead of 20... IF it really should change like that. I have no idea.

Anybody have knowledge of what the EGR kPa really means?

 

As I think to know, it is indeed a relative value, but some another way

It is a difference (hence "relative") between intake manifold air pressure with EGR valve opened and closed.

The air pressure in the manifold is lower, if the EGR valve is closed and a bit higher, if it is opened (the pressure is negative relative to the atmospheric pressure in both cases).

The throttle valve is closed, the motor is dragged, rotating, no ignition, no fuel injection, the cylinders are sucking the air from the manifold producing low pressure in the manifold. If the ECU then opens the EGR valve, the exhaust gases are flowing into the manifold, the low pressure rises a little bit.

This is the difference, we see.

Mat

 

Just stumbled across this randomly on a reddit thread. A bit worried. Dont really have the money to take it to Hybrid Pit to get the cleaning.
2015 Prius with 115k miles. Havent done anything other than oil changes. 95% of the time I drive like an old lady hyper miling 60% HWY 40% City. The other 5% I can drive like a bat out of hell.

My first test today with the Car Scanner Android App
EGR Monitor Bank 1
Value 22.16 kPa Min 0.99 Max 655.35

 

The values are actually excellent!
If I should be worry, I would be worry, that they are too good for your 115k miles.
22 kPa is, what people see after good cleaning the EGR cooler and the neighborhood.

It could be worth to check it with a different tester.

Mat

 

The EGR passage in the intake manifold could be getting along to clogging, and the instrument readings will still be fine.

how much was that?

consider DIY? First two links in my sig have tips and info; on a phone turn it landscape to see signature.

 

Thank you Mendel. Roughly how long would it take me to swap out the EGR/Inspect it? Can it be done within a few hours? I need to change the spark plugs so I might as well go a bit deeper to the EGR. Is there anything else I should replace?

HybridPIt quoted me "$685 is the full cost of just EGR service with new hoses, pcv, coolant change, and fuel injector cleaning."

Would hate to pay that kind of money only to find out it didnt need it.

A few more numbers from recent trips:

22.12
21.21
21.32

 

That’s a good price, especially considering the extras. $600 is what people have been paying for EGR cleaning only.

The second time I did the cleaning, it took me roughly one short work day, and wrapped up reassembly the next morning.

Strategy helps. The EGR cooler’s bracket has a nut that’s difficult to reach, can be a real time burner, but it can be removed in advance, without needing to remove anything else, and can be left off. If you also remove the stud that nut was on (E8 Torx socket required), you’re then able to (later) remove the cooler without needing to remove its two rearmost studs. This saves time, and reduces the chance of rearmost gasket dropping into the engine bays nether regions.

also: get the cooler of first, and get it soaking. It will take time to bubble out the carbon. My approach is to cork one end, fill it with hot tap water, concentrated solution of Oxi-Clean Versatile Stain Remover, prop in corner of laundry sink. 5~6 one hour soaks and rinses was enough for mine. If more stubborn, hydrogen peroxide solution (lye) would likely be more effective.

Have a read through the top two links in my signature for more info. You can do this with near-zero expenditures, though it might be good to change the intake manifold gaskets, and maybe the PCV valve.

if that sounds like a tall order, again: Hybrid Pit is a good choice. It may seem pricey, but you are just getting into head gasket failure mileage, and that’s very pricey. Some just sell at that point. Some dump in gasket sealer and sell…

 

With flow test numbers that good, I think I'd be in no hurry to extensively disassemble the EGR system.

Taking off the intake manifold is a much smaller project, and can be worthwhile because some unbalanced clogging in the small passages there can be possible without the flow numbers showing a problem. Having it off to check is the simple way to find out about those. So I could still be talked into doing that smaller job.

 

Ill have a go at the at the difficult nut first and see how I fair. It can be left off permanently??? Should I frame it on the wall? hehe.

I see you all over this forum and I thoroughly appreciate your lengthy responses.

 

Or you could concentrate on the intake manifold egr ports as that's where the 'imbalance' happens, as Chap explained.
You have a good quantity of flow so the cooler is fine, correct? Save that for 2 years or more.
The 90° pipe and EGR valve itself are easy to get to and clean.

If time is what's important to you, you could have an already cleaned intake manifold ready to install once you remove the current one.

It will be interesting to see if you can quantify the amount of imbalance in the egr ports within the intake manifold.
You could crudely put a 'lip-lock' on each small passage to see if you 'feel' a different flow rate. Sounds yucky,, but it might show you if you have this theoretical 'Imbalance'.

You might find that you wasted your time and your car if fine, as the flow rate indicated.

 

Yup, that nut (1) never be missed.

Bonus points for backing out the associated stud. For that you need an E8 socket. They’re typically 1/4” drive. I used a diminutive 1/4” ratchet wrench, backed it out pretty much one click at a time. Dissimilar metals make it nerve racking, so you want to press very firmly, go slow and careful at first. It fights all the way out. Again, having that bottom stud out means you don’t have to remove the rear studs (4) on the cooler.

also, good to remove and reinstall the nut and stud (2) at the EGR valve (apply thin coat of antiseize to stud threads), ditto for the bolt (3) at top bracket on cooler.


all this prep can be done any time, will make subsequent main job go quicker. And gets you familiar with the system.

 

So how often do you recommend all these 'subsequent' cleanings be done?

Or,,, you could just disconnect the electrical connector at the EGR valve and never worry about 'an Imbalance' with intake flow again.
Some are reporting that it works great.
It seems the Brazilian Prii don't even have an EGR circuit.

 

I would do the EGR cooler cleaning every 60 to 100 thousand miles.
Or simply, as it is needed - say, If the test value goes under 19 kPa?

The Intake manifold could be done a little more frequently, while it is simpler to do, and we do not have any test done by the computer to check.

I would NOT recommend this method!

Yes - and I'm pretty sure, they have a different programming of the computer driving all vital ICE parameters (in Brazil they have a significant amount of ethanol mixed into the gasoline, I think).

Mat

 

Why is that?
Can you give the details?
Ol'what'shisname has been running his prius that way for years. Others too.

The system still has O² sensors and a Knock Detector. What's the worst that can happen?

And as always,,, the vast majority of Prius owners have never heard of this 'off the book' servicing.
It kind of sounds like the head gasket is the weak link with this engine, no matter how much preventative off book maintenance one does.

 

50k miles max

 

I don't know any better details as this:

at 5 minutes and 35 seconds.

Somehow, I believe what this gut is saying

Mat

 

Dead link

 

By me it functions perfectly...

^^ maybe here once again?

Mat

 

The video plays for me, but I don't see that he really tries very hard to answer Bill Norton's question; the script at 5:35 doesn't go much deeper than "trust me, Bad Things can happen".

The Car Care Nut seems to say some sensible things and also some goofball things in the same video. He deprecates (twice!) obsessively cleaning the cooler so shiny you could host state dinners there, and I think I'd agree with him that far—but his line that "as soon as you start the car, drive a mile, it's going to be exactly the same" clearly can't be taken seriously. If it took 80,000 miles to get the way you found it, it won't be back that way after the next mile of driving. The whole point of checking the flow result numbers this thread is about is to be able to gauge how long that takes.

I'm not one of the Toyota engineers myself, but it may be worth recalling that they programmed the ECM to respond proactively whenever it has detected an EGR problem, and keep the ignition retarded without waiting for the knock sensor to retard it. If they were convinced it would be enough just to react to the knock sensor, I'm not sure they'd have gone that extra length.

 

There is a difference between a shop and doing it yourself.
The shop has a lot of liability, the individual doesn't.

"IF" the cooler gets as dirty as it is as soon as you start the car, why in another
video does he replace it???? I'd like to have those coolers he replaced.
EGR valves also. And probably other parts.

I'd like to have the money to replace everything instead of just clean it up.

I do things on my car I wouldn't do on someone elses. Because I know what I did and
what would happen if it failed. So I can be ready for it.