While I am changing spark plugs, should I check anything else?

There are many discussions on PC about Gen 3 oil consumption related issues. The consensus is that it may results in build up in EGR (including pipes and cooler), PCV valve, and intake manifold. Many people think it is a good idea to add an OCC. I am not sure if your car is built before or after the piston correction from Toyota.

Do you see oil consumption on your car?

 

While plugs are out is always a convenient time to do a compression or leakdown test. You can track the results and, over more than one spark plug change, get an idea how the engine is mechanically holding up.

The two test methods give you roughly the same information. Compression test gauges grow on trees, but on a Prius you need a scan tool that can command the engine to crank at 250 rpm in order to use it.

You can do a leakdown test without a special scan tool, but need a leakdown tester and a compressed-air source. It is also quieter and can tell you more about where any leakage is going.

Leakdown tester orifices aren't standardized, so comparing results only makes sense if they came from the same tester model. (Exception: leakdown testers made for aircraft engines. Those are covered by a standard.)

 

While the cowl and wipers are off, and considering you're at 122K miles, I would DEFINITELY do a full clean out of the Exhaust Gas Recirculation components, and the the Intake Manifold (it has EGR passages), and consider an Oil Catch Can Install. The latter does not require the cowl being off though, can be done later, but will help at least in keeping the PCV from barfing oil into the intake.

More info:

Bad Flywheel | PriusChat

 

I recently acquired one of these:



It has gradations on the barrel, around 350 cc capacity, and very tight, no piston leakage to speak of. Hopefully link works:

And found it very effective for applying either pressure or vacuum, especially in consjunction with a one or two vacuum check valves. I'm not sure how much pressure is needed for a leak-down test, but I might just give it a crack with a mod'd compressor tester hose/connector. Maybe acquire the proper gauge set too, or a the very least be able to check for leakages.

 

“Let's not give the OP busywork” - chapmanf

 

I wouldn't count much on results from that. There is an amount of leakage normally to be expected (piston rings have end gaps, etc.). The leakdown tester is expecting to create a flow of compressed air and quantify the flow (which it does with two pressure gauges, upstream and downstream of a calibrated orifice, so the difference in the two pressures tells you the leakdown rate).

It won't use up compressed air at a very high rate, but it will need something that can give you 80 to 100 psi and keep it steady long enough for you to read the gauges (and listen for sounds, if there seems to be notable leakage).

 

I'm glad you like the line, but if I remember right, the thread where I used it was one where somebody had an explicit trouble code indicating to check for X, and people kept spamming in posts about checking W or Y or Z when those were clearly ruled out already.

In this case, I think Mendel believes those suggestions to be on point to the general topic of this thread. It's not necessary to agree, but even without agreeing, it would be hard to say that's quite the same thing.

 

John V Rosenbaum, I might be a bit sick but I actually thought changing the plugs on the Gen3 was not that bad. Compared to many of the GM vehicles I used to work on as a mechanic, the process of removing the cowl is very straightforward and makes access to the plugs a breeze. Once the cowl is off the process of changing the plugs takes at most 10-15 minutes with the right tools.
I would inspect the old plugs for indications of excessive oil use or deposits. Make sure the rubber boots for the ignition coils are in good condition. If you are replacing the plugs just based on mileage rather than trying to repair a check engine light or misfire, then it should be a fairly quick and easy job.
As others have suggested I would also strongly recommend that you remove the intake manifold and EGR pipes and clean them. I cleaned the intake and EGR pipe on my Gen3 at least 3 times as I recall in the 280K I drove it. I never removed the EGR cooler to clean it as I did not see excessive build up, but that call is somewhat subjective. I did find some mild plugging in the EGR pipe and some severe plugging of the EGR ports that deliver the exhaust gases to each cylinder, the port for #1 cylinder being the most plugged.
I am not sure if you are asking what other maintenance should be done at 122K, but I would suggest a coolant change for the engine and inverter loops, and changing the transaxle fluid if this has not been done before. There are lots of good videos on You-Tube that give you a good preview of what you are in for.

 

Engine coolant change is 2 years or 20k miles prior, so may just recently be done. It is possible to remove the cooler with min disturb to engine coolant: drain to qts prior leaves the cooler high and dry. Collect drained coolant in clean container and return to reservoir when done, leaving vent bolt open and squeezing hoses as you fill. If vent bolt is missing 2012 onward), disconnect a topmost hose to accomplish venting.

 

@NutzAboutBolts videos linked, in the link I posted in post #4. And some tips, and relevant repair manual excerpts.