2014 Gs300H F Sport Engine Heat Problems

[Richard Hearne]

Hi, I have a new GS300h F Sport (5k miles) and have the following problem which my local agent won't acknowledge.

As soon as I switch the car on - the engine and air-con fans start up, even when the engine is freezing cold, as a result the engine fails to warm up properly and my mpg drops thru the floor. All the electronics relating to how the engine/hybrid system works seem to be related to the engine temp, so in my case don't work very well. Once the engine is hot, everything seems to work properly, good(ish) mpg etc. However, if I go down a long hill in overrun, the engine temp drops and everything stops working again. Agent says this is how they work, which I feel is a feeble excuse.

In all my years of motoring (in cars with electric fans) the fans have never switched on until the engine or air-con temp required cooling. Has anybody has a similar experience and can offer an explanation/cure.

[rayaans]

Hi, I have a new GS300h F Sport (5k miles) and have the following problem which my local agent won't acknowledge.

As soon as I switch the car on - the engine and air-con fans start up, even when the engine is freezing cold, as a result the engine fails to warm up properly and my mpg drops thru the floor. All the electronics relating to how the engine/hybrid system works seem to be related to the engine temp, so in my case don't work very well. Once the engine is hot, everything seems to work properly, good(ish) mpg etc. However, if I go down a long hill in overrun, the engine temp drops and everything stops working again. Agent says this is how they work, which I feel is a feeble excuse.

In all my years of motoring (in cars with electric fans) the fans have never switched on until the engine or air-con temp required cooling. Has

When you say poor mpg, what do you mean exactly? How much are you getting?

The air con fan will always turn on when the car turns on unless it is set to AUTO, at which point, it should heat the air up first and then gradually turn the fan setting up and then regulate by itself.

Can I ask how you know that the radiator fan is on? Did you take a look under the bonnet while the car is on? It may be that the fan helps to heat up the engine, like how a fan oven works but probably better if a mechanic answers that question.

[stevet]

Sounds normal to me. The fans are always on if the aircon is on. Try it turning the aircon off.

[LexIS200Sport]

I think he's talking about the cooling fans in the engine bay (behind the radiator and aircon condenser). In which case you are right, Richard, neither should come on when you first switch on your car during a frosty winter's morning. The aircon fan should only come on when the compressor kicks in and the radiator fan when the coolant temp is hot enough.

I certainly don't think this is normal, so I would be persistent with your Lexus dealer and pursue a warranty claim for this problem. Take the matter up with Lexus HQ if they don't budge.

[Hayne]

Interesting issue. That doesn't sound like correct operation to me. My GSh temperature doesn't budge once it's up to temperature, even when coasting down a long hill in cold weather.

Engine temperature rise will take slightly longer than a conventional petrol car due to the high efficiency of the simulated Atkinson cycle engine, but the sound of fans coming on could be something else; you have a lot of stuff going on under the bonnet relating to the Hybrid system that may sound like a fan. If the mechanical thermostat is working correctly, then it is unlikely that continuous fan run would cool your engine like that without coolant running through the radiator.

As Ganesh suggests; push this back to Lexus.

Giles.

[ColinBarber]

Need a bit more clarity on exactly which fans are coming on please. The radiator fans shouldn't be running but you could be mistaking other noises for this.

The 2.5l engine in the 300h does tend to lose heat quite quickly if it isn't running, more so than the 3.5l engine in the 450h.

[Richard Hearne]

Hi Guys, thanks for the feedback so far. More details...

Open the bonnet, switch the car on an the two radiator fans start up. (not talking about the heater fan in the car) So trying to cool both the engine and air-con coolants, but the car's at 4 degrees (cold).

Everything in the car is set to auto mode.

The Eco mode light used to be on frequently when low power required, so used the electric motor more frequently, now with the cold system, the Eco light/system stays switched off and uses the engine mostly, which as its cold runs inefficiently.

Currently getting about 20mpg (short journeys), however before it got cold was doing approx 40mpg.

On longer journeys when the system gets 'hot' it all start to work as in the summer (before cold weather), but as soon as I go down a long hill, or have been using electric power for a bit the engine cools down and it all stops working the way I would expect it to, and starts using more fuel again.

[Richard Hearne]

Note to Stevet - hadn'd mentioned it before, but if I switch the heater off (incl air-con) the two fans stop, the car heats up more quickly (surprise, surprise) and back to running efficiently, except I'm all steamed up and have cold passengers. All in all, it points to the systems in the car working incorrectly when its cold. I may of course just be that the thermostat is snafu, releasing cold and warm water for cooling, when its actually not even hot enough.

[rayaans]

Note to Stevet - hadn'd mentioned it before, but if I switch the heater off (incl air-con) the two fans stop, the car heats up more quickly (surprise, surprise) and back to running efficiently, except I'm all steamed up and have cold passengers. All in all, it points to the systems in the car working incorrectly when its cold. I may of course just be that the thermostat is snafu, releasing cold and warm water for cooling, when its actually not even hot enough.

Yep, sounds dodgy on all accounts. My car doesn't behave like that. As mentioned, push it to Lexus. Best bet is to go in when you're free, preferably on a morning and explain that its not working how it should. They'll have no choice but to investigate it if you do that.

[Hayne]

Have you tried turning off the air con compressor, but leave the climate control on? Could be related to a faulty temperature/pressure sensor for the air con system (maybe)

Clutching at straws, but worth trying.

Giles.

[ColinBarber]

There is nothing wrong. The radiator fans will always spin if the AC is on, but they aren't spinning anywhere near full speed and has no impact on the engine warming up because the coolant won't be going around the radiator until the water temp is 90+ deg and the thermostat opens.

The engine will take longer to heat up if you have the interior heating system on because the temperature is being taken out of the coolant to heat the cabin.

If you are near freezing then your economy will fall. When the engine is first started it will run rich, the engine will run more to give you heat for the cabin (turn the climate control off and the system will go into EV much more), the hybrid Battery will have less effective capacity because they just don't work as well in the cold, and you have many other things using energy such as lights, fans, demister etc.

[LexIS200Sport]

The radiator fans will always spin if the AC is on, but they aren't spinning anywhere near full speed

Even if the compressor isn't engaged?

[ColinBarber]

The radiator fans will always spin if the AC is on, but they aren't spinning anywhere near full speed

Even if the compressor isn't engaged?

No probably not, but I'd class that as the AC not being on. ;)

Certainly if you are set to auto on the climate control and you haven't manually switched off the AC settings then when you first 'start' your car then the compressor will come on and the fans will start, even before the petrol engine fires up.