Getting Too Hot....

[AustinGT]

I am back again to the genius board in need of help- my LS has never even come close to overheating, and the previous owner said the gauge never moved from the middle, and even in 110 degree summer heat w/the ac on the gauge never moves. Today as I was leaving the gym I noticed the gauge was halfway between the middle line and the top . I turned the ac off, and after about 5 minutes of driving it cooled down to normal. I started it about an hour later with the ac going full tilt, and it was fine. The system was "serviced" by the dealer two years and 12k miles ago including new coolant and thermostat, and my reservoir is still full. I am thinking possibly the fan didn't come on, but any input/advice would be greatly appreciated!!

[etex]

The engine temperature will typically increase after the engine is turned off. This is not something to be concerned about. You probably just happened to notice it at that time. Experiment with it and see if it is not a consistent happening. Give it about half an hour and re-start, then immediately note your temperature (engine) gauge.

[AustinGT]

Okay, today the car did something similar, but this time when I started it the temp gauge was right in the middle, than it shot up to the top and settled down a little higher than the middle, than went to normal. I have never seen the gauge jump around like that- is this a sign that the gauge electronics are bad, because I know the temperature would not shoot right up to the top and settle down in a matter of seconds..... I also left it idling with the air on for a minute or so after driving and the gauge was okay.... if it is the gauge how would I go about fixing it?

[Threadcutter]

Okay, today the car did something similar, but this time when I started it the temp gauge was right in the middle, than it shot up to the top and settled down a little higher than the middle, than went to normal. I have never seen the gauge jump around like that- is this a sign that the gauge electronics are bad, because I know the temperature would not shoot right up to the top and settle down in a matter of seconds..... I also left it idling with the air on for a minute or so after driving and the gauge was okay.... if it is the gauge how would I go about fixing it?

If your 400 is '95 or newer, it is OBDII. You could beg/borrow/buy an OBDII code reader that will also do some diagnostics such as tell you what your coolant temperature is. Although, if the gauge is getting it's info from the ECU, the code reader would probably show the same as what you are seeing on the gauge. You are probably correct in that it is unlikely that the temp is spiking up and dropping back down that quickly. I hate to say "don't worry about it", but in all likelihood, it's not something that is going to cause you problems. If you've got a mechanic you trust, take it to him and pay him for an hours time and have him give you his opinion.

[AustinGT]

Thanks threadcutter- I restarted it about thirty minutes later, and the temp gauge was fine. The main reason I was a little concerned was that I will be out of the country for about a month and my little sister (17) will be driving the car, and I just want to make sure that it doesn't overheat or something on her. I also replaced the battery about a month ago, and both incidents regarding the gauge have happened since then, so I am hoping that it is just a voltage adjustment or something that is causing the happenings.

[landar]

Thanks threadcutter- I restarted it about thirty minutes later, and the temp gauge was fine. The main reason I was a little concerned was that I will be out of the country for about a month and my little sister (17) will be driving the car, and I just want to make sure that it doesn't overheat or something on her. I also replaced the battery about a month ago, and both incidents regarding the gauge have happened since then, so I am hoping that it is just a voltage adjustment or something that is causing the happenings.

Austin,

My bet would be riding on an errant coolant temp sensor or connections thereabout. Take a look at this

thread:

http://us.lexusownersclub.com/forums/index...4&hl=sensor

[Rice]

It does look like the problem is with the electronics rather than with the engine heat itself.

Just a sidenote.

Turning on the A/C actually lowers the temperature and not increases it like most seem to believe.

When you turn on the A/C, your lectric fan for the A/C comes on and cools the radiator even more.

It's a tried and prooven fact.

[Rice]

Threadcutter, LOVE your avatar ;)

I want that creature for president just to p i s s myself off

[LS4hundy]

Thanks threadcutter- I restarted it about thirty minutes later, and the temp gauge was fine. The main reason I was a little concerned was that I will be out of the country for about a month and my little sister (17) will be driving the car, and I just want to make sure that it doesn't overheat or something on her. I also replaced the battery about a month ago, and both incidents regarding the gauge have happened since then, so I am hoping that it is just a voltage adjustment or something that is causing the happenings.

I just wanted to say that you are very brave man for letting a 17 year old gal drive your lexus for a month. When my fiance borrows my car, i have rules.

Rule #1 Must be the car parked furthest away in any parking lot.

Rule #2 No eating in the lex

Rule #3 No playing with buttons.

Its a very healthy relationship!!!

[Gweeto]

I HAVE A NEW QUESTION:

MY '91 LEXUS LS400 OVERHEATS UNLESS YOU ARE DRIVING 25MPH OR HIGHER. NOW, MAYBE OVERHEAT IS THE WRONG TERM - IT HEATS UP AND THEN EVENTUALLY WOULD OVERHEAT COMPLETELY IF I DIDN'T HAVE THE GAS PEDAL PUSHED IN TO GET THE ENGINE TO ABOUT 2RPM'S OR SO. ONCE IT BEGINS TO HEAT UP, THERE'S NO STOPPING IT UNLESS YOU CAN GET TO A STRETCH OF ROAD WHERE YOU CAN GO 25-35 MPH FOR A PERIOD OF TIME.

NOW HERE'S THE KICKER AND BACKLINER TO THIS ISSUE: THE HEAT AND/OR AC ONLY WORKS WHEN I PUSH IN THE GAS PEDAL. IN THE WINTER THE HEATER WON'T WORK UNLESS, AGAIN, I'M DRIVING ABOUT 25MPH OR SO...

NUMEROUS "PROCEDURES" HAVE BEEN DONE TO TRY AND FIX THIS. NEW WATER PUMP, BACKFLOW, NEW THERMOSTAT. I ALSO KNOW THE PRIOR OWNER HAD A CONSIDERABLY AMOUNT OF WORK DONE IN REGARD TO THE ISSUE AS WELL WITH NO PERMANENT SOLUTION.

THESE PROBLEMS JUST SEEM TO REVOLVE AROUND THE ISSUE WITH THE GAS PEDAL - ANYONE HAVE ANY ADVICE? :chairshot:

[Rice]

I HAVE A NEW QUESTION:

MY '91 LEXUS LS400 OVERHEATS UNLESS YOU ARE DRIVING 25MPH OR HIGHER. NOW, MAYBE OVERHEAT IS THE WRONG TERM - IT HEATS UP AND THEN EVENTUALLY WOULD OVERHEAT COMPLETELY IF I DIDN'T HAVE THE GAS PEDAL PUSHED IN TO GET THE ENGINE TO ABOUT 2RPM'S OR SO. ONCE IT BEGINS TO HEAT UP, THERE'S NO STOPPING IT UNLESS YOU CAN GET TO A STRETCH OF ROAD WHERE YOU CAN GO 25-35 MPH FOR A PERIOD OF TIME.

NOW HERE'S THE KICKER AND BACKLINER TO THIS ISSUE: THE HEAT AND/OR AC ONLY WORKS WHEN I PUSH IN THE GAS PEDAL. IN THE WINTER THE HEATER WON'T WORK UNLESS, AGAIN, I'M DRIVING ABOUT 25MPH OR SO...

NUMEROUS "PROCEDURES" HAVE BEEN DONE TO TRY AND FIX THIS. NEW WATER PUMP, BACKFLOW, NEW THERMOSTAT. I ALSO KNOW THE PRIOR OWNER HAD A CONSIDERABLY AMOUNT OF WORK DONE IN REGARD TO THE ISSUE AS WELL WITH NO PERMANENT SOLUTION.

THESE PROBLEMS JUST SEEM TO REVOLVE AROUND THE ISSUE WITH THE GAS PEDAL - ANYONE HAVE ANY ADVICE? :chairshot:

First of all, turn off the caps.

To answer your question, or half of it...

It apears that you have two issues.

1 - Your fan clutch is gone. You need a new one. Your car overheats because the fan is not doing its job. Even though you will see it speening, it is not speening as fast as it should. Driving 30mph pushes air through your radiator and cools the engine. When you are stopped, the fan should be doing this job.

2 - I have the same problem with interior heat on my 97. I do not get any heat when at idle. Once RPMs go above 1K, the heat begins to flow. My A/C works fine. I have not tried to diagnose this myself, but if someone out there has a solution, I would like to hear it. If I had to guess, I'd say that the cooling system may be partially blocked as it goes into the heater...

[AustinGT]

Thanks threadcutter- I restarted it about thirty minutes later, and the temp gauge was fine. The main reason I was a little concerned was that I will be out of the country for about a month and my little sister (17) will be driving the car, and I just want to make sure that it doesn't overheat or something on her. I also replaced the battery about a month ago, and both incidents regarding the gauge have happened since then, so I am hoping that it is just a voltage adjustment or something that is causing the happenings.

I just wanted to say that you are very brave man for letting a 17 year old gal drive your lexus for a month. When my fiance borrows my car, i have rules.

Rule #1 Must be the car parked furthest away in any parking lot.

Rule #2 No eating in the lex

Rule #3 No playing with buttons.

Its a very healthy relationship!!!

Don´t worry- I said that she could drive it on the condition (s) that:

-The car cover was on it at work

-It was parked in the shade whenever possible

-No heavy throttle when cold

-No fast food in the car!!

Nice to know that I am not the only one who has conditions about the car!!