My 2010 Prius, which has clocked 150,000 miles, recently began to rattle upon starting up on cold mornings. After experiencing this issue a few times, I received the CEL codes P0300 and P0302. I inspected the coolant level, which appeared to be stable. I then took the car to a local mechanic for a professional opinion. The mechanic diagnosed the issue as a VVT actuator failure, estimating the labor cost for repairs to exceed $2,000 due to the approximately 17 hours of work required. Given the current value of the car, they suggested that it might still be drivable for another year or two in its current condition. However, they also advised me to consider purchasing a new vehicle. Over the past couple of weeks I have been monitoring the coolant level after each drive. I've noticed a gradual decrease in the coolant level over time. When I contacted the mechanic to inquire if the VVT actuator failure could be causing this, they confirmed that it could. They also mentioned that they have encountered several Gen 3 Priuses with similar symptoms and CEL codes. While one of these cases involved a head gasket issue, all the others were due to VVT actuator problems. I am seeking additional opinions on whether this diagnosis seems reasonable. Any thoughts or comments would be appreciated.
The VVT actuator can not cause coolant to leak into the engine cylinder. You have a bad head gasket. If you continue to drive the car, the head gasket will only get worse. You need to decide if you want to spend the money to fix the car, or get a different car.
there are tests for a bad head gasket, although it is the most common failure with your symptoms. if the mech is willing to do the work and not take payment until you are sure the coolant level is stable, it might be worth a shot.
The VVT system has very tight tolerances. Delayed oil changes is the main cc cause of failure from narrowed passages It's like plaque clogging the arteries in the human body. A major blockage will cause a stroke or a heart,heart attack. In a car, current synthetic oils easily last 20,000 miles. Sludge buildup begins immediately- it can clog VVT passages to the point of failure in as little as 7,500 miles. Continued successive delayed oil changes keeps building up over time. Frequent oil changes from the beginning of the engine's life is the only way to avoid VVT failure.
Something stinks. These things are pretty sensitive to the cam timing; if it is wrong they pop their own error code. So why are they chasing a VVT problem at all? Symptoms are an (unfortunately) good fit for a blown head gasket.
All your comments convinced me that it is head gasket issue. I was able to replace it with the one from Felpro. At the same time, I replaced PCV value, water pump, spark plugs and thermostat. I also cleaned intake manifold, EGR value/pipe and fuel injectors. It was quite challenging work and I had to spent ~50 hrs. It's been almost 2 weeks since then and my 2010 prius has been running perfect. Many thanks to those who commented.
Yes I cleaned the cooler as well. I did not mention it in my previous posting but one thing that I noticed when I replaced the spark plugs was that I could see 'Pink' stain in the groove of the coils due to the coolant leak into the cylinders. In fact, I got P0302 code first a couple of months ago. I saw the pink station only on the coil in cylinder #2. Then at the point I got P0300 and P0302, I saw the pink mark on all the coils. This could be another way to check if coolant is leaking into the engine.
It seems the best was to test for a leaking head gasket is to put pressure on the cooling system and use a bore scope to see if you can see coolant leaking into the cylinders from the gasket. You'll likely also notice the top of the pistons look cleaner than the others. Usually, it starts leaking between #1 and #2 cylinders.
