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Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Boffin, Mar 11, 2020.
That's what it is ... but where on the car is the sensor you have been calling the MAF?
Its attached to the backside of the intake box lid.
Oh good. Reading #37 where you were writing about having to take the intake off to get to it, and then about some other sensor "closest to the air filter" that maybe wasn't plugged in, I was afraid you might have had it mixed up with something else.
It turns out the intake air temp sensor is combined with the MAF sensor; in fact the IAT is the part you can actually see (the blobby thing on a wire in plain view). The MAF wires you can only see if you peer very carefully deep into the passageway in the plastic sensor.
Because they're combined in the one sensor assembly with only one connecting plug, it's hard for just one to be unplugged.
Question: I've watch the NutzAboutBolts video on EGR valve and cooler cleaning. Wouldn't it be smart to drain the coolant instead of clamping all those hoses? The clamps create more crowding leaving very little room to reach some of those nuts and bolts. My question is do I drain the inverter coolant or the engine coolant?
I drained 2 liters of the engine coolant (into a clean container), left the full EGR system high and dry. Just pour it back into reservoir when done.
Also, when lifting the throttle body off the intake manifold, the TB coolant lines have plenty of slack; no need to disconnect.
a bit more clarification in the EGR link in my signature.
Edit: post deleted
Well, my 2014 PiP is at 203k KM (~127k miles), so I was overdue to try cleaning this EGR pipe I have heard so much about with the Gen 3. Car is running completely fine, just a preventive maintenance consideration. As a side note, the car has 87% HV usage over it’s lifetime, so about 177k KM (~110k miles) of gas-burning operation… so perhaps not that far overdue.
I studied the Nutz About Bolts YT video (and a few others) to understand the process and build up confidence to try it. I was most nervous about dropping a bolt into the engine, which thankfully didn’t happen.
In fact, the procedure was actually very easy - one of the hardest parts was trying to disconnect that Mass Air Flow sensor, which was very stubborn, and he sorta skipped over that step in the video, lol.
In the end, there was some reasonable carbon buildup, but pretty minor IMO, and did not seem near to being totally clogged, so that is a good thing I guess. I don’t consider myself an aggressive driver who open the throttle fully very often or pushes the engine to it’s limit (which I presume could lead to more carbon?), if that is a factor.
For cleaning, I used some drill bit brushes, brake / parts cleaner (same as the NAB video), and an old toothbrush, and it seemed to do the trick well.
Overall, the job took about an hour or less, as I was taking my time double-checking steps along the way. I’m sure I could do it in less than 30 mins if I did it again.
Some pics below for reference, for age/mileage.
Next project… I need to decide if I want to tackle changing the spark plugs myself, since it seems I will be waiting a while for my 2023… I have replaced plugs in a car before and that’s easy, except it seems necessary to remove the wiper assemblies & cowl to access them properly, which appears to be a PITA that I am not sure I want to take on myself.
hmm, there's more to clean than the pipe....
I was wondering why it takes everyone else hours...
Nice that you wanted to tackle that job.
Removing the wiper assembly is really very easy. Just a lot of nuts and bolts.
But cleaning that pipe really doesn't do anything. It's the cooler that will clog up.
The passages are very small. So cleaning that is like changing the oil filter and not the oil.
Or oill and not the filter. And don't forget about the 4 holes in the intake manifold.
It really is not as difficult as some make it out to be. If you take your time and just worry about
1 thing at a time, you be finished before you realize it. And make notes about where everything
If you use oven cleaner and a pressure washer you'll clear out and CLEAN the cooler in less
than an hour. Use gunk and a gun bore brush in a drill to clear out he passages on the intake
and you'll finish the job in a few hours.
And intake manifold.
probably worthwhile to replace all its pliable gaskets.
There’s a link in my signature with EGR cleaning info. On a phone, hold in landscape orientation to see signatures.
Thanks for the replies… yes, I realize there is a more thorough job, but I figured this was a good first step for now, especially since it did not seem too bad for now. May revisit next summer if I still have the car then.
It is, the pipe is relatively easy to access, and gives you some idea what the rest will be like. Judging from the pipe pic, the rest is worthwhile.
In prep for the rest, any spare time you have, remove the hold-down nut on the EGR cooler. This can be done without removal of other components, and can (in my opinion) be left off. It would seem easy, but takes every dang socket, extension and ratchet, loosening adjacent stuff, just a pain. Best to deal with it and be done.
Tougher to do, but worth it, is to back out the stud that nut goes onto: you'll need an E8 torx socket for that, likely on a 1/4" ratchet wrench, and with all the cables and clutter in the way, and due to the disimilar metals, it'll be slow going, one click at a time. You want to careful with this, go slow.
Getting the nut off is time-consuming, very difficult to get at so best gotten out of the way. Having the stud off as well means (I believe, will verify the theory soon myself) that you will not need to remove the rearmost studs, at the exhaust manifold, just take their nuts off. This in turn means the rearmost gasket is much less prone to drop down (possibly never to be seen again...), and reinstall of the cooler and that gasket is MUCH easier. I would still take those studs off, apply a little anti-seize to them, and reinstall, while the cooler is off the car.
I would also temporarily remove the EGR valve nut, and it's associated stud"
put a light coat of anti-seize on the stud, and reinstall both. (torque values are in one of the attachments linked in first line of my signature).
The intake manifold EGR passages, one per port, are easily cleaned with some sort of thin bottle brush, say 1/4" diameter bristles. I used a brush designed for cleaning stainless steel drinking straws; others have used gun barrel bore cleaning brushes. Start it in, add a squirt of brake cleaner, work it around. Use brushes/rags and a little brake cleaner on the rest.
For the EGR valve: brushes/rags and a little brake cleaner. Some have pried off the black cap of the EGR valve. I may try that again next time, but was stymied by stubborn screws the first time. I found it possible to just gently pry up the valve and clean around it, fwiw.
For the EGR cooler: some swear by pressure washer. Others have done oven cleaner soaks. What worked for me, with light build up, was repeated soaks with a concentrated Oxi-Cleaner Versatile Stain Remover (powdered detergent additive, available at Costco, Walmart, in cartons/tubs, depending on the size) hot tap water solution, with one end corked. Pour it in, prop it up in a corner of rectangular bucket or laundry sink, let soak about an hour (it'll bubble up, then subside) rinse and repeat. Takes about 5 one hour sessions to get to as-new clean. If shopping corks, here's the cooler end hole diameters: This stuff is rinse-down-the-sink benign; a laundry additive. Don't dump it down storm drains though.
Note: don't use Oxi-Clean on anything other than the stainless steel cooler; it's mildly corrosive, reacts with non-stainless steel, aluminum.
Intake opening diameter (at exhaust): 20.9 mm <
exit opening diameter (at EGR valve): 25.7 mm
What to do with brake cleaner:
I looked this up, and the consensus was to pour it over a small tray of clay kitty litter, leave it in a sheltered, outside location to vapourize for a few days, then bag the kittly litter and put it out with the garbage.
Again, check first link in my signature, for tools required, torque values, tips, strategy to avoid any coolant spillage (unless you want to change coolant at same time).
Thanks for the detailed reply, @Mendel Leisk, you really are the guru on the topic around here.
My pipe looked better than that one and the egr cooler was totally clogged. The intake was not clogged in the four ports, however the intake had plenty of liquids pooling.
An easy thing the car lets you do, and will give you more of an answer than anybody's judgment of how bad your pipe looked, is to ask for your EGR flow test result numbers.
Based on the actual data, you could decide you want to move ahead more quickly with the full cleaning, or you could find support for your judgment to let it go for later.
I appreciate all the comments and advice, the community here remains awesome. I’m a DIYer, always willing to learn.
It seems to get the EGR flow data it require techstream? Which I don’t have… is a ScanGauge II any help here?
"Mode 6" monitor test results are a standard OBD-II thing. I don't think you can read them with a ScanGauge II (maybe you could, by studying the programming manual long enough), but you don't need Techstream; any scan tool or phone app that can read Mode 6 test results will be enough.
Wasn't really clear, and too late to edit; here's the location of that stud and nut, the most difficult to access one (highlighted):