*For Informational Purposes Only here, Names and such withheld due to privacy but this car came into our shop this week and I wanted to share some pics with the community in hopes it would help someone somewhere somehow* Gen 4 Fans, viewer discretion advised. Customer's 17' Prius Prime with 150,000 miles came in for a cold start rattle and coolant loss. Originally thought to be the dreaded heat exchanger valve that stuck (negative lucky for him, HVAC system pressurized and held over night), welds were also okay. Moved to the dead or dying water pump theory (with 150k miles it was close and could have run a few more thousand miles but advisable to change now due to the high labor hours for Gen 4 Water Pump swap we decided to do this now and likely small contribution to this issue). So 2 strikes as to cause..leading to simple coolant not being changed (likely ever) and non warm up situation with very aggressive driving habits along with crappy Toyota gasket materials as you can see. Same thing as a Gen 3 here. EGR not an issue and clean. Not sure a 100k water pump and coolant flush would have helped here. With that being said...look at those pistons! CLEAN @ 150k miles...yep, still Gen 4 is King with the EGR routing getting burnt off by the cat. At 150k miles on a Gen 3, the tops of the pistons are charcoal even on a healthy engine. Unbelievable! Now FEL-PRO reps are you listening? Manufacture a Gen 4 Head gasket like yesterday! Car now runs great back to it's old self, hopefully the owner starts driving it like a Hybrid Unfortunately for us Gen 4 in Gen 3 car guys, we're going to muck up the pistons with some mileage with that Gen 3 EGR on them, but ..oh well.
Any pictures further back, the full top of block with head gasket in place? Toyota (according to YouTuber The Car Care Nut) has revised gen 3 head gasket; the new style is a silvery grey colour, appears to be a uniform material, ie no black surface layer (that erodes). Perhaps they’ve done similar with gen 4??
Any engine can blow a head gasket but no one has chronic problems like the gen3 Prii, twenty year old Covics or certain Subaru’s in the modern era. Coolant erosion or overheating combined with preignition are common causes for any engine,
These are the only pics the mechanic forwarded to me after hours, I only saw the finished product later unfortunately. When I order the latest revision or whatever is called for regarding a head gasket from Toyota themselves, this is what they send us..it's still black. Likely the same darn thing. There is an external scenario or factor that's doing it I'm assuming (other than material composition). The silver ones still have the issue..especially if EGR is plugged and water pump fails. Heat will destroy anything..
Apples and Oranges if you're comparing a G4 to anything else. The only validation to this statement would be coolant erosion or overheating...but on this vehicle with 150k miles overheating did not occur and POSSIBLY coolant was starting to erode. 97% of all Gen 4's who all made it past this mileage did so with flying colors. I'm still thinking driving habits..I noticed a "Hoonigan" sticker on the car (those that know, know)
Also like to mention, with Primes..people I know like to only run on electric mode for months at a time only or switch to ICE at highway speeds with no warm up going 75 mph. That can't be healthy for an ICE..this is why I think we see the Prime having this issue in this case more than a normal Hybrid Prius Gen 4.
Hoonagin.......................yup. I heard from the Service advisor at Mercedes about blown turbos on the GL550 from people who "roomp" on the gas and punch the turbo all the time.....he never sees that failure in little old lady or soccer mom GL's.......go figure.
on my plug in prius, i had engine shake on light load at 87k. i attribute it to running ev most of the time and many shortened warm up cycles
Imagine you left the same gas in the tank for long periods of time as well since you didn't run the ICE much? That will cause a misfire quicker than greased lightning if a fuel injector is bad (as well as oil burning) in that cylinder if left untreated.
The manual recommended using it up every 6 months, so I did. And the engine would run on its own every 124 miles, needed or not, I’m not sure what the problem was, but I decided to dump it in case it was the head gasket
