16GSFSPORT

This forum is fantastic, I've been lurking since I picked up my new Lexus and this is my first post. Does anyone else notice the temp gauge seems to run a little high on their GS? It's not abnormally high or in the red, but I noticed that is constantly past the halfway point. My old civic and mini van seem to run in the lower third of the temp gauge. Just seeing if anyone else notices this or am I becoming super **** all of a sudden

Bartman619

....Hmmm. Mine runs a little below half way. Even when running with the A/C on.

jkeller

Congrats and glad you're here.

Toyota's have had "weighted" temp gauge for years. When the engine reaches operating temps the temp gauge needle won't move up or down unless there is a big change in temp. So for example- the engine temp reaches 200F, the gauge shows a middle of the normal range reading. You stop at a red light in Phoenix in August for 3 minutes. The real engine temp increases to 225F. The gauge won't move at all. As soon as you start moving, airflow across the radiator increases and the engine temp drops back to 200F. The gauge reading doesn't change. It also works the same way in North Dakota in winter, except engine temp decreases while stopped at a red light because the engine idle and load have decreased. Still the gauge won't move. It's designed to stay "stuck" on the needle position for a set temp range.

Bartman619

Yep, the temp gauge is a glorified Idiot Light.

16GSFSPORT

Thanks for the breakdown, responses like this is why this forum is so fantastic

bclexus

That's a new one on me - I've never heard of that before. If true, that would mean there would have to be additional circuitry. Circuitry that senses, references and compares the actual engine coolant temperature signal, but can switch the signal to the gauge (when certain signal parameters are met) between the actual (accurate) signal and a bogus (inaccurate) steady-state signal in order to keep the gauge's needle in a fixed position. That, to me, seems like an unnecessary expense to perform an unreliable result to monitor engine operating temperature.

jkeller

Today, I would say it's software driven, but it's been like this for at least 20 years. We are both in hot summer Texas. Have you ever seen your temp gauge get above half way? I haven't. This is my 4th Lexus, 98, 01, 07 ES and my 14 GS. All of them behaved the same way. If the temp gauge had a real scale with degree numbers on it would moving up and down per outside temps. engine speed etc. Mine is the same reading once it warms up, no matter what the other conditions are. That's really not possible for the cooling system to maintain exactly the same operating temp and therefore the same temp gauge reading.

http://g35driver.com/forums/g35-seda...auge-liar.html

http://www.bimmerforums.com/forum/sh...Gauge-Accuracy

Im2bz2p345

Great information jkeller! Those are really interesting details. Ty for sharing.

~ Im2bz2p345

jkeller

The 07-08 ES's had water pump weep hole/ gasket leeks. They weren't severe enough to leave a pink antifreeze puddle under your car. Just enough over a period of months to drop your coolant level...you're driving down the freeway, you're temp gauge is pegged right at it's normal everythings zen reading and then... all the dash warning lights come on and before you can say what the.,.. your engine seizes on account of low coolant, and now you have a Lexus ES paperweight edition. All the while that temp gauge never gave you any kind of warning, none, nada. I never had an issue with my 07, in fact I think it was quite rare, still till this day I don't understand where was the coolant sensor at? I mean how can the gauge say normal temp, when in reality the fluid level was critically low. I learned my lesson from that ES form. If I ever have a car's temp gauge get more than moderately above it's normal spot, I'll turn off the AC turn on the heater pull off and check on the coolant level.

bclexus

I can't imagine why any car maker would want to make the engine temperature gauge lock in a position once the engine comes up to normal operating temperature and not read the correct temperature. My guess is that the car's electric cooling fan, along with an excellent water pump and engine block cooling jacket, does a superb job of keeping the coolant temperature very steady. I suspect if you unplugged the electric cooling fan you'd see the instrument gauge needle climb in warm climate stop-n-go driving.

jkeller

I see your point, it sounds crazy at first, but have you ever seen your temp gauge move once it reaches operating temp? There is no way the car's temp is the same today as it will be come August idling at a stop light for 10 minutes in a Dallas heatwave. Not trying to pick a fight BC. Lexus is not only one doing this, in fact it might be the norm now with all auto makers.

bclexus

No, I have not seen my engine temperature gauge's needle move once the engine coolant gets to normal operating temperature...during hot or cold ambient conditions. The gauge's needle is far left when the engine is cold, and it drops when I shut off the engine for a short while, so that tells me the thermistor sensor and circuit does indeed work from that perspective. I honestly believe the cooling system is just doing a superior job of maintaining a very narrow coolant temperature...and that is why the needle appears to be stuck in one position. I truly believe if the thermostat became stuck in the closed or almost closed position, or the electric cooling fan failed, that the needle would move up to indicate a higher than normal coolant temperature.

rjm

After warmup my temperature gauge rides a bit below halfway and stays there no matter how I drive. It doesn't matter if the outside temperature is 110 degrees in summer or 20 degrees in winter. Whether it's designed to stay pinned on "normal", or the outstanding design of the cooling system is responsible for that, I don't know. But the gauge running slightly below the midpoint keeps me happy, and I suspect it was designed to do just that.

bclexus

Today's engine cooling systems can (and do) maintain a constant coolant temperature (212°F/100°C) regardless of whether the outside (ambient) temperature is 115° or -15°. This constantly maintained engine temperature allows the use of 20 weight engine oil.

jkeller

I guess the one way to know for certain is to hook up a scan tool with a live streaming digital temp reading. Then drive under different weather temperature conditions to see if the scan tool temp goes up and then see if the car gauge goes up too.

edit

With the car overnight cold start it with the scan tool hooked up. Then as the car idles see at what true temp the car's temp gauge reaches its normal gauge reading, then do the above.