Engine Knock on Cold Mornings

I'm in SoCal too...

The "moisture" is coolant in my case. It started after 150k. Original owner regularly serviced with documentation, lots of freeway miles...

Healthy HV battery, tried a fresh 12V auxiliary battery (thinking the extra power might help motor functions).

Maybe if the coolant continued to circulate minutes after shutdown it wouldn't build up pressure. Opening the gas engine coolant reservoir, it pops with the pressure. The coolant isn't malodorous but it's only got 300-400 miles on it.

Subaru engineers must have transferred across the hall to Toyota

 

The time to worry about it is when it suddenly starts at 150k.

I get that a young engine might have some atmosphere-induced condensation. The 1.8 seems to run hotter than other cars, including my gen 4, by 10°F.

In my soon-to-be former (in 2 hours, it's gone) geriatric car, there is extreme pressure/vacuum buildup in the coolant reserve tank (it makes a pop louder than a big old bottle of champagne - I'm new to this particular engine, maybe it's normal). The rough starts happen even in 65° weather after the car has been sitting for all day in the sun. I marked the coolant tank and discovered that, after 50 miles of driving, I lost about a millimeter of coolant. Since it was recently bought, it's got maybe 150 miles on it since they took it in trade. The coolant hasn't changed odor yet.

My suspicions are: If exhaust is busting through while the engine is running, you'll get that odor sooner or later. When the car sits parked, that remaining system pressure then forces the coolant past the HG.

Being a former Subaru owner (never again), I know the symptoms of a slowly-blowing HG.

 

How many miles on it? Level of coolant in the reservoir stable?

(Wrong forum btw, I've alerted moderators.)

 

Dang, even updated new rings and seals, 2015 still knocks. You wonder if that's why turd gen ended in 2015.

 

How was that measured?

 

I suspect the knock is clogged EGR related. Revised pistons and rings just help with oil consumption.

 

I marked the reservoir, cooled the engine a similar amount of time after driving a similar route the night before, parked at the same location. Also referenced pre-purchase photos where the coolant level was even higher on a similarly cold engine.

That, along with information the previous owner conveyed to me about a Toyota dealership diagnosis added up to a BHG☹️

The selling dealership has since refunded me the entire purchase price.

 

Just a heads up...

I was (until last night) still enamoured with the idea of having a Prius V. So, in spite of coming across a few anecdotal stories and my own personal experience with the blown HG, I continue shopping for one.

Using Toyota's online portal, I am able to see the original configuration of the vehicle. So far, found 7 Prius V's that were being sold as one grade higher than they actually were. Prius V 3s that were actually Prius V 2s and V 5s that were actually V 3s. The one I bought was actually the opposite. It was being sold as a V 2 when it was a V 3.

On top of that, using multiple online resources, I have discovered 3 vehicles that were openly diagnosed as having blown head gaskets and one additional was diagnosed with it. Only one person actually had work done on it according to the notes available.

Being resourceful is a must in my family and I have been just absolutely flabbergasted with the car market, private party and dealerships.

Now, if a very low mileage certified pre-owned 2016 Prius V comes through at a great price, I will consider it. That 7 year, 100,000 mile warranty will give me that level of confidence...

 

Buy new.

I guess that would rule out the v though, no longer sold in US?

 

There are still CPOs coming off lease. 35k-45k miles. The California 10y/150k hybrid + the 100k mile 7 year drive train warranty makes the risk of the HG issue a little less of a threat. Unless I'm completely misinterpreting the warranty.

I wish that the 4th gen motors/systems made it to the V. Seems like the engine is doing well although we only have 23k now.

While the Outback is the top wagon right now, the V matched the cubic feet of cargo from 2010-2014 OBs at least. I can only imagine how much money the V's 40+ MPG over the 24 MPG of the Subaru would have saved me.

 

Did you figure out what it was ? was it your COILS?