This advice applies to any auto, not just Priuses. When your engine runs hard for a while (1/2 hr or more), it accumulates a heat load. As long as you keep it running, this load is continuously removed by the cooling system (coolant plus radiator (heat exchanger)) and dumped into the surrounding air. When you stop, the heat removal stops. Some earlier auto models had an electric radiator fan that ran whether or not the ignition was on, but this runs down the 12V battery and is a safety hazard for anyone working under the hood. Now the car is sitting there with a large lump of hot metal under the hood. The hood is insulated and there are no vents or louvers in the hood of a modern car. What happens? Everything under the hood comes to a temperature much higher that ambient, much higher than it ever reaches when the car is running. There is a mess of plastic and rubber components under the hood. Although I'm sure Toyota uses the very best they can afford, these components do chemically decay; the rate of decay is an exponential function of the temperature and a linear function of time. Those of us who drive our cars for 15 years have experienced a rubber valve cover gasket which turns into hard, brittle plastic. Similar things happen to all rubber and plastic components. Thus: the less the non-metal underhood components are exposed to high temperature, the longer they will last. When you get off the road on a hot day after hard running, open the hood for an hour. If you get a new car every 2 years, you will never know the difference. But if you run your Prius for the 10+ years that they are (over) engineered to run, you will.
I call BS My last Toyota was 16 years old when I sold it. I currently own a Toyota Crown, built in 1968, with all original hoses etc.
I'm more concerned about keeping those IGBTs in the inverter cool than the hoses and gaskets, but that's just me.
Prius engine room is easy to be cooled down because of the engine-off coasting and the idling stop. Therefore, the grill blocking is more important than the opening hood after run. Ken@Japan
Correct. The engine shuts off, remember so during the winter time, we block the grill to help keep the heat in. (Don't forget that in the winter, you're extracting heat from the engine to heat up the cabin anyway so I don't think the issue with heat pooling is as great). So don't worry, we don't block it in the summer.
Ken: I'm guessing they keep the airconditioner off. Grill blocking and airconditioning don't mix. Howard
If you are concerned about dumping heat after shutting off your car you can get an electric drive motor for your engine water pump (The 2010 Prius already has an ICE electric water pump) and remove the serpentine belt. Putting the electric motor under temperature control will then automatically dump the excess heat. Here is a link to some example units, but you will have to determine if they fit: Water Pump, Electric Drive Kits - SummitRacing.com It would be a good idea to upgrade the little 12v battery (Optima yellow top - 12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008 and 2009 with installation kit and free shipping) to avoid starting problems later. JeffD
Howard, We sometimes use A/C, therefore we still open 50% of grill. :focus: More importantly, the grill blocking eliminates the engine room cooled down and we can reduce the warming up fuel for next driving. The opening hood of OP's opinion is not agreeable. Ken@Japan
The Prius engine generates very little waste heat compared to "normal" vehicles. This is pretty apparent if you park in an enclosed garage and note the amount of heat generated by a V-8 powered vehicle, my Mustang GT convertible for example, then compare to the relatively tiny amount of heat produced by the Prius. Because of this, Prius owners will also find that radiator and other cooling system hoses will typically last for a longer duration compared to other vehicles. Its not because the hoses are better quality - but rather because there's less heat produced by the engine.
have to agree that the last thing i want is for the Pri to cool down faster, it is sometimes difficult to warm it up and keep it that way... in some cases, the engine runs barely over half the time to begin with.
Back to the op's original contention, the short answer is BS! In most conventional cars the worst thing you can do after a hot, long freeway run is to pull up to the pump after running full bore for a while. The concentration of heat around the cylinder walls and heads is very significant, leading to possible spot overheating as the coolant stops circulating around the block. A much better way is to roll off the freeway with the car coasting in the slip stream allowing the coolant to circulate for a bit. The drive with a fairly high rpm for a block or two, (but gently) just keep the rpm up to keep the coolant circulating fast. The when you pull into the pump let the car idle for 30 seconds or so to dissipate the heat. Prius is a different animal. I, by habit, pull into the pump and let it sit for a minute,, but usually the engine quits anyway. I agree that more problems with the Prius are due to not enough heat rather than too much. Icarus
I'm going to stay out of the specifics of this debate and just say I think I'd rather deal with the periodic replacement of a hose or decayed non-metal part and NOT have to worry about leaving my hood open after every drive of more than a 1/2 hour. In this case the Cure sounds more like the Poison.