Rx400H - How Long Does It Take To Warm Up?

[Melchior]

I'm wondering how long other peoples' cars take to warm up to their normal operating temperature. I suspect my car's thermostat may be partially stuck, but the local Lexus dealer wasn't any help.

The weather's cooling off here, and about 50 degrees most mornings now, and I've noticed that my 2007 RX400h takes quite a while to reach its normal temperature, and sometimes has trouble maintaining that temperature. My normal operating temperature is about 2.1 "ticks" up on the dial.

When I leave my house in the morning, I've got about 3-4 minutes of up/hwy/city/flat, before I go down a hill for 2-3 minutes. The rest of my trip is elevation-neutral, with some light ups and downs.

When I get to the big downhill, the engine usually shuts off for the downhill trip, but sometimes idles all the way down the hill. The temperature gauge gets about 1.5 ticks up the dial. The engine cools off while I go down the hill, and if the car's feeling in the right mood, I've got half a mile of electric-only operation after I get down to the flat. This brings the temperature down to about one tick. After another 5 minutes of driving (mostly on the engine), the gauge gets to 2.0 or 2.1 (operating temp!), but my next 10 minutes of driving is flat with some stop-and-go-and-coast where the engine always comes to life. During this period, I tend to coast quite a bit, and my temperature will often drop back to 1.5.

The result is that it normally takes 10-20 minutes to get to operating temperature, in 50-degree weather. Thankfully, the ventilation system in the car warms up pretty quickly!

By comparison, my last car (Honda Accord L4) would hit operating temperature within a mile of my house.

How does this square with your experiences?

[lemon]

I noticed the same thing last winter (first winter with my 2006 400h. When the weather got colder, it took much longer for the vehicle to heat up, than even a traditional vehicle. I was going to replace the thermostat myself to see if it made any difference (and get a coolant change done at the same time) till I realized how much stuff has to be moved out of the way to get at the thermostat housing. In you case, whenever you are in electric mode, the engine is not heating up since it's not running. In my case, however, when leaving work, I am on a highway within 2 minutes and the engine runs constantly, and still I was finding it very slow to warm up. Now, I'm not sure if it's a thermostat problem or just a hybrid thing (our engines supposedly run more efficiently thus producing less heat, plus we have larger grill openings in the front bumper than the regular RX for additional airflow over the inverter radiator (which is a separate radiator from the engine radiator and the A/C condenser.

[cduluk]

Agree, it's normal.

The morning temp. ranges from the high 30's to low 40's this time of year in RI, and i've noticed the same thing with my Rx400h. You can definitely HEAR the engine working harder during the first 5 minutes of driving.

Thankfully, the Rx400h's heating system is "somewhat" independent of the engine temp for producing hot air (Rx400h heater is electric). When i had my Rx300, the heater didn't produce any heat until the engine was hot. I used to drive in "LOW" for the first 5 minutes to get the engine and transmission to work harder in efforts of getting more heat. It really worked too! Definitely bad for the car, but well worth it for the quick heat.

Can't really do that in the 400h (since there's no LOW gear, just "B") but i've found if i accelerate harder the engine would heat up faster.

Also, when in PARK with the ignition ON, the engine temp doesn't go below the 1/5 mark. I guess the engine kicks on and off enough to keep it it from falling below...

[maseace]

You may be interested in the ScanGauge II, which allows you to read the exact engine coolant temp, among many other things. The normal operating temp of my 400h is 177-180°F, in any weather. Never saw it go above about 182°, even in 100+° heat. Its usually gets there in about 5 minutes, depending on temp, speed, and heater use. I find that when stopped at a light, the gas engine will shut off during warm-up, even with the coolant temp only in the mid-130° range. I believe the normal temp for operation in electric-only mode is 157°F.

http://www.scangauge.com/products/

You can try the grille-blocking technique to help retain the heat in the engine compartment in the winter, to help improve MPG, reduce warm-up time, and get cabin heat quicker (only useful for hybrids). I have the bumper air slots blocked right now. Just use ordinary dark gray pipe cleaner you can get for $2 a bag, cut in half lengthwise. Cut a piece to length for each slot and stuff it in. There is a lot of info about grille-blocking on the PriusChat website. Here's one thread: http://priuschat.com/forums/gen-ii-prius-modifications/38645-my-attempt-grill-blocking.html

[lemon]

Agree, it's normal.

Thankfully, the Rx400h's heating system is "somewhat" independent of the engine temp for producing hot air (Rx400h heater is electric). When i had my Rx300, the heater didn't produce any heat until the engine was hot. I used to drive in "LOW" for the first 5 minutes to get the engine and transmission to work harder in efforts of getting more heat. It really worked too! Definitely bad for the car, but well worth it for the quick heat.

Can't really do that in the 400h (since there's no LOW gear, just "B") but i've found if i accelerate harder the engine would heat up faster.

Also, when in PARK with the ignition ON, the engine temp doesn't go below the 1/5 mark. I guess the engine kicks on and off enough to keep it it from falling below...

Just a quick correction - the 400h heater is not electric - the system still depends on hot coolant to produce heat. Where the electric comes into play, however, is the 400h has an electric water pump in the cooling system (separate from the engine coolant pump which is traditional, driven by the timing belt) that keeps circulating the hot coolant into the heater core to keep producing heat even when the engine is off (when the engine is off, the engine coolant pump is not turning and coolant is not being circulated so the electric pump is needed - in a traditional vehicle the coolant being circulated by the engine coolant pump is also circulated through the heater core for cabin heat.

When in park with the ignition on (and in colder weather) the system will not let the coolant temp fall below a certain point so that cabin heat can be maintained. Also, the catalytic converters need to be kept hot for emissions control, so you will notice the engine run more frequently in colder weather and start with less of a push on the gas pedal. Due to this, you'll see a corresponding drop in your mileage as well - in my case summer is around 8 litres/100km and winter is closer to 10 litres/100km.

[cduluk]

Agree, it's normal.

Thankfully, the Rx400h's heating system is "somewhat" independent of the engine temp for producing hot air (Rx400h heater is electric). When i had my Rx300, the heater didn't produce any heat until the engine was hot. I used to drive in "LOW" for the first 5 minutes to get the engine and transmission to work harder in efforts of getting more heat. It really worked too! Definitely bad for the car, but well worth it for the quick heat.

Can't really do that in the 400h (since there's no LOW gear, just "B") but i've found if i accelerate harder the engine would heat up faster.

Also, when in PARK with the ignition ON, the engine temp doesn't go below the 1/5 mark. I guess the engine kicks on and off enough to keep it it from falling below...

Just a quick correction - the 400h heater is not electric - the system still depends on hot coolant to produce heat. Where the electric comes into play, however, is the 400h has an electric water pump in the cooling system (separate from the engine coolant pump which is traditional, driven by the timing belt) that keeps circulating the hot coolant into the heater core to keep producing heat even when the engine is off (when the engine is off, the engine coolant pump is not turning and coolant is not being circulated so the electric pump is needed - in a traditional vehicle the coolant being circulated by the engine coolant pump is also circulated through the heater core for cabin heat.

When in park with the ignition on (and in colder weather) the system will not let the coolant temp fall below a certain point so that cabin heat can be maintained. Also, the catalytic converters need to be kept hot for emissions control, so you will notice the engine run more frequently in colder weather and start with less of a push on the gas pedal. Due to this, you'll see a corresponding drop in your mileage as well - in my case summer is around 8 litres/100km and winter is closer to 10 litres/100km.

Oh fantastic... Why couldn't lexus just put a damn space heater in there?? I guess the engine would need to stay on longer to make the extra electricity, but it would be worth it for more heat!!

[lemon]

Electric heater to use before the coolant heats up...that would have been a good idea - maybe you're right about it sucking too much battery power though. I know in the RX450h, they are also now utilizing the exhaust gas somehow to gain excess heat from it.