Wanting to buy Gen3 prius - some Qs

Is there any particular reason that you're wanting to move on from your gen2? Gen3 generally have issues burning oil at higher mileage, carbon-clogged EGR circuits, and blown head gaskets. If your gen2 is well taken care of and doesn't have any issues, I'd stay with it. I might make an exception if one found a 2015 with low miles and was handy.

Toyota updated the pistons and rings in 2015 which might have mitigated the oil burning. Good consistent maintenance might also mitigate it and EGR cleaning isn't that difficult to do, it's just obnoxious and takes a weekend being under the hood.

 

Second the above. Also, for the hybrid battery, Dr Prius (phone app)?and a Bluetooth OBD adapter (Carista is good) can give you a quick overview of the individual voltages and resistance within the pack.

 

gen 4?

 

Just to make sure , is it the good one ? very interested by that, my Prius is 7 years old and I want to check if the battery is in good shape , thanks .
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Yeah that’s what I’m using. On Dr Prius website there’s a page reviewing adapters, recommended that one.

 

Prius Gen3 Issues

Oil Consumption, ABS Brake Actuator, Inverter, Head Gasket, Water Pump, Hybrid Battery

Summary

Gen3 Prius with the 1.8L engine from 2010-2014 have bad rings causing excessive oil consumption around 150k-200k, the Brake Actuator is a $2300 failure in the same time frame, the Inverter is slightly less likely but was also defective from the factory. The brake actuator and inverter have a special replacement warranty ("customer support program") that expires ten years from first use. On a 2012 that could be Sept 2021 to Sept 2022 for most. I would take the vin to Toyota and find out if these parts have been updated. Changed already is best as either failure will be costly after June 2022.

The water pump is easy to replace, is electric driven and is really not a significant cost unless you don't pull off and stop immediately. Too many want to go two more miles and blow their engine.

Hybrid Battery is good to 180k-220k and the only good repair is new from $1600 diy to $3000.

Detail

Oil Consumption, EGR and Head Gasket

Toyota's Prius and Prius v 2010-2014 models often have high oil consumption that result in egr and head gasket problems. By 2015 new pistons and rings were used in the gen3s. Often the gen3s exhibit short duration and occasional "cold start rattle" that is likely early head gasket leakage. Owners either ignore it or clean their egrs and add pcv oil catch cans, usually too late in the game if engine "rattle" is already occurring. Overheating can be an end result of head gasket failure because of lost coolant through the cylinders.

Head Gasket Root Causes

1. The number one likely root cause are bad piston rings that allow excessive blow by into the egr and pcv. This creates carbon in the valves and cylinders. Too often owners do not check the oil enough and run low until a low oil pressure failure compounds things. Bad valve stem seals add to oil burning.

Toyota admitted bad rings on the 2010-2014 Prius engines and changed the parts free if high oil consumption occurred during warranty. High consumption was defined as a quart every 1200 miles or worse, which almost never happened during the powertrain warranty.

2. The number two is the egr system itself which employs an elaborate stainless egr cooler feeding the egr valve. The egr cooler is liquid cooled and picks up exhaust gases upstream of the cat, effectively condensing portions. The near foot long cooler clogs limiting egr circulation. Egr cools the combustion chamber but clogging leads to pinging and knocking. Which is destructive before the knock sensor can adjust the timing.

Toyota moved the egr intake to downstream of the cat in the gen4 Prius. This provides cleaner exhaust gas for recirculation. Better piston and rings further reduced hydrocarbon blowby. All v's are gen3.

3. The pcv system also dumps oil fumes into a plastic intake manifold, creating a catch can of sorts which eventually overfills into a cylinder. This often fouls the plug and causes further damage, sometimes even hydrolocking.

Reduced blowby and improved intake manifolds reduced this issue in later generations.

4. While the Corolla has the same engine, the Prius is a stop start engine while the Corolla is not. As a result the 1.8L Prius engine has frequent thermal cycling as the engine cools and heats up while driving. Sometimes cycling twenty, thirty or forty degrees many times during the drive cycle. The head bolts are steel while the block and head itself are aluminum. The head bolts and the block/head metals see significant thermal expansion cycles. The Corolla 1.8L stays at a consistent temperature.

Thermal cycling remains a hybrid issue especially for vehicles in traffic or for those who have extended wait periods.

Opinion

I think frequent oil changes while the engine is clean will keep it that way longer, even with known piston ring issues. Reduced oil consumption will keep the oil out of the exhaust, which in turn will reduce the gunk in the cylinders.

Experience shows that small coolant leaks into the cylinder can exist for months with little impact - but its certainly a game of engine hydrolock russian roulette that often bend connecting rods and sometimes blows holes through the block.

Then there is the fact that Toyota rerouted the egr intake to downstream of the catalytic converter by the fourth generation. Let the cat clean up unburned oil and fuel before dumping it back into the cylinders via the egr. Of course the rings and pistons were upgraded late in the gen3 run. Reduce oil burning and fuel blow-by. Makes sense. Almost like science at work.

 

I've got no oil consumption, at least not perceptible. Put it this way: the level on the dipstick does not budge, at all, ever. But the EGR (and intake manifold) was carbonning up when I checked it around 70K kms.

I'd say the 3rd gen EGR system, without any help from oil consumption, is inherently flawed, clog-prone, and the main contributor to head gasket failure. It's just my opinion, and I'll test it by continuing to regularly clean the EGR and intake, see how that shakes out.

 

I’m a maintenance fanatic too , using OEM products, very good results... 2014 , 160000kms still running like new, no oil consumption at all , EGR will be done really soon , but I really like this car , easy to work and really good mpg....even with very long winters like here ..! Hope you’re gonna love it !!!

 

Has anybody ever drawn a picture of what that would look like?



The last time I did anything with my intake manifold, I did slurp out all the gloop from the bottom of the manifold below the throttle body, where the eel is. Yes, I know I can't draw an eel. There was about a thimbleful of gloop. As far as I know, all Prii tend to gloop the intake manifold. My 2001 Gen 1 did too, by about the same amount.

(The water pump is circled because I filched the image from a water pump manufacturer. Best I could find to show the shape and orientation of the manifold.)

I'm fairly sure they did that because catalyzed-EGR became a thing in auto engineering circles over that period of time. The catalyst does more than clean up the gases, it changes the chemical make-up and how they affect combustion when reintroduced to the cylinders. Journal papers about it. Not just a Toyota 2ZR thing.

 

Ah. If that's the case I'd say go for it if you find a really good deal. Though I'd try to look for 2016s if you don't mind the look of them as it'd likely save you some issues in the long run. I used my 2010 for some Lyft driving and I thought the gas savings was well worth it.

Regarding the commonality of the issues, it's hard to say for sure since I don't think any official stats exist. But if you look at Toyota recalls and warranties regarding the brake actuator and inverter, and the posts around the web regarding head gaskets, I think these are common issues and that most Gen3 Prius north of 120k miles commonly suffer from EGR issues because it's an inherent design flaw. Most folks probably don't keep their cars for long after 100k miles so I'd bet that a lot of people who buy them never got far enough to deal with anything other than regular maintenance.

For 2015s, the updated pistons might help tremendously since it could limit the oily gunk that ends up circulating through the EGR. But someone with a 2015 and a lot of miles would have to take a peek at their EGR to give us a clue about that.

 

I think it's just pretty hard to make EGR trouble-free. There's gunk in those gases and stuff will get gunked. My mom's 1979 Colt would start running like absolute email-protected every time you turned around because the EGR system had to be reamed out.

I had a 1984 Bronco II where somehow they avoided giving me too much trouble with the EGR valve, but the potentiometer position sensor attached to it could never seem to last more than a year. It would end up with just a couple small glitches in its response (just like we see on Gen 2 coolant control valves), but they'd be enough for the (one) computer to throw codes, and there I would be buying another EVP sensor, I remember them as like $130 a pop. Not openable/cleanable that I could see.

 

If I may join in: maybe naive to think the PVC deposits oil/water/gas in an orderly fashion to the intake “sump”? More like it shoots in there aerosol fashion, some condenses and runs down, but some just passes right through?

 

I would counter that with a used one from a wrecking yard IF you can verify history and length of idle time at the yard. But it’s still risky. Mine was $425 from a 14 with 70k miles verified by the CarFax showing total loss declaration.