I have also posted this elsewhere.

My 2005 LS 430 has recently been getting very warm when working a bit harder than standard. No, not thrashing it, just working a little harder, like going up a hill. The dash temperature gauge sits on its normal position, just above the centre mark. However, I have an HUD display plugged into the diagnostic port, and it shows the rising temperature.

I have just put in a brand new radiator because it was leaking from a crack in the top tank, no difference. My original first thought was a crack in the head or block, but no sign of water in the oil, nor oil in the coolant, and I can't smell anything apart from antifreeze in the coolant, but that may not necessarily be correct, my sniffer may not be as good as it might be, at my age!. It looked clean when I drained it. My next thought was water pump, but it was changed 30,000 km ago, so it should be fine. Or a thermostat not opening fully, but that I haven't checked.

.The fans are turning on at about 93 degrees.

The strange thing is the different reading on the dash temperature gauge, although it appears to work fine up to that normal point.. Checking the actual water temperature suggests the HUD is reading correctly.

Does anybody have any ideas? Thank you.

 

What is the coolant temperature you are seeing? FYI the gauge cluster is a "fuzzy logic" affair meaning it shows an average or put another way not the most accurate.

 

How much time did you spend bleeding the cooling system?

 

9 minute mark addresss the bleeding issue, this guy uses compressed air.

 

The first thing you should have checked would be the thermostat...

 

Hi. Temperature on the HUD up to 101, and checking the actual water temperature when that's showing 95 or so is about the same. I think with working a bit harder, it would go higher.
The cluster gauge might not be the most accurate, but it stops at the normal point, and doesn't budge even at the highest temps.

 

Yes, that's probably my next thing. I had to change the radiator anyway, and hoped that might overcome the problem if it was partially blocked, but no!

 

Okay, thank you, I will look at that. I wondered about bleeding, because my LS400s had a bleeder on top of the motor, but these don't

 

Errr, ummm, none yet! I will check that though. I wondered about bleeding, because my LS400s had a bleeder on top of the motor, but these don't

 

101C is well within the normal range of operating temperatures for an internal combustion engine.
Most don't enter the Red part of the gauge until they hit 105C (220F) and even then you are still not damaging your engine, but you are mighty close so shut her down and wait for her to cool off.

Most have thermostats that open at around 85C and have switches that turn the fans on at around 95C.
It sounds to me like only one of your fans is operating but since these cars have computerised control, that can be difficult to determine.

 

Thought I would chime in. When I bought my car used in 2016, there was zero coolant in the reservoir, and zero in the radiator. Needle always was slightly below mid, like it is today. Yes I was horrified, but in retrospect, having no coolant that could be seen, did not have any effect. This tells me the car is not sensitive to having no coolant that can be seen. And my personal explanation is everyone says it's super long life, so not even dealers touch it for 10 years.

So my first stab at a temp issue would in fact be radiator and thermostat--it's mechanical so nothing more than physics. Maybe the thermostat is not OE? These are all dicey today, as far as what's purchased online, is the same as what came with the car. Fans to me come more into play while stopped, not driving.

Some of these simple mechanical devices play a big role in thermodynamics when not electronically controlled. For example, my wife's GM's radiator cap needed replacement. Symptom? Coolant above the full line hot. Coolant above the full line cold, sitting overnight. That was a odd problem even the internet didn't help with. Everyone said air in the system. Nope. Radiator cap that did not allow coolant to return from reservoir to radiator as car cooled down. Even I hadn't realized the job of the radiator cap was to do that.

 

Thanks. Both fans are working, and come on at the same time, at 93 degrees. Then off at about 90/91. They don't spin anywhere near as fast as some cars, which roar! These are dead silent! I don't know if they have slowed down over the years, or not, as I haven't kept an eye on them, although they have never been heard! However, I think it may be a bit better since doing some manual bleeding, but I haven't worked her very hard yet. And it may need a bit more bleeding, although I don't think so, but I still have to check that out.
The dash gauge never moves once it gets to about 85 degrees, just above the middle mark, and that mark is about 80 degrees. Maybe I'm just being a bit paranoid!

 

Yeah, I had that problem less than 6 months ago, so replaced the radiator cap. On the old radiator, of course, so transferred it to the new rad, It seems to be working both ways okay, but I've only had one run on relatively flat terrain, mainly motorway, since bleeding etc. Had that a few times over the last 65 years or so, and have had to replace the caps. I haven't checked the thermostat yet, but if I'm not happy with how things are now, I will pull it and check that it opens at the correct temperature, which I believe it does, and that it's opening fully. .

 

Thats normal, the fans on LS cars are supposed to be very quiet since a roaring fan is annoying. I can leave my car in direct sunlight on a 90+ degree day with ac set for 70 and it can't be heard if you stand 10 ft away

 

Yesterday I decided to check there was no more air to bleed out, Then I figured I would try and get it hot by sitting with it running at 3000 RPM. It slowly went up, and fans came on at the usual slow fan speed at 93 degrees. I kept going and it eventually got up close to 100, at which time I was surprised to find the fans started running at a very much higher sped, sucking through a lot of air! I then let it idle and the fan speed dropped considerably, as the temp reduced, then dropped further to the usual slow speed. So, there's apparently at least 3 speeds, but I wonder if there might be an even higher speed if over 100 degrees! I had forgotten some cars have variable speeds, but it still doesn't have noisy fans! At the slow speed, it's not possible to hear them, no matter how close you are. You have to look at the fans, or feel the air coming through. I've still got to get on a decent uphill to see what happens,especially at very slow speed, like in crawling traffic, but I think all may be good now. Fingers crossed!

Thanks everyone for your replies. If I find anything different later, I'll get back.