Hi all, 2012 prius with 200k miles. About to tackle the head gasket job the gen 3 is plagued with. Of course I was planning on cleaning the hell out of the EGR valve while I'm in there (never been done). Just an opinion question really... Would you replace the valve and cooler while you're in there? I know one answer will be : "if you feel like spending a few hundred go for it" Mind you-no signs of a faulty one. Passes emissions yearly, good acceration, no knocking. Kind of a tough question to answer i know. Comes down to $$$ I guess
The EGR valve may need replacement, if there’s a groove worn like this: this is looking at the interior of the cap that’s inside the EGR valve. For the EGR cooler cleaning should do the trick. With 200k I’d go with lye solutions, cork one end, fill, prop up and allow to soak for an hour, rinse and repeat as needed. Running a slim wire through to open it up some, may be needed. The EGR pipe, being stainless steel as well, you can use lye solution, but probably overkill. Everything else I’d use brake cleaner, just enough, and brushes, rags, and elbow grease. Definitely don’t use lye on anything that’s not stainless steel. Also don’t use bleach on stainless steel. see the links in my signature for relevant links, both for EGR and head gasket. Bottom link is full engine section from Repair Manual. (On a phone turn it landscape to see signatures)
In case it's not clear what groove Mendel meant in that photo, here's a photo with the "ski jump" undamaged on the left, while the one on the right has a rut worn through it,
Non reason to replace the valve if it's working. Won't hurt if you do. Just get the whole "egr kit" because it's cheaper that way. The cooler can be cleaned. It's nice to have a 2nd one on hand to have cleaned and ready to install.
If you can see the rut there, you have ocular proof the valve isn't working. That stop is what keeps the rotor from going past the valve-closed position. The rut gets formed a little at a time by the rotor going a little too far and plowing out a little of the plastic. Next time it can go further (because there's already a bit of a rut) and make more of a rut. By the time it's plowed all the way through like in that photo, the rotor goes right on past the whole valve-closed position and doesn't stop turning 'til it's tight down on the threads. A poster in another thread figured that was about 120° too far. That other thread also tried to determine the number of steps per rotor revolution, and ended up guessing 48. If that guess is right, then 120° is sixteen steps on the wrong side of valve-closed. If you are testing the EGR with scan tool active tests where you say how many steps to open, normally by step 16 you're getting pretty close to killing the idle. On a rutted valve 16 steps might not even have started to open it yet.
