saleenssc

What should the normal operating temps be for a 98 LS400. On my car they fluctuate between 195-203 degrees depending on outside temp, stop-n-go traffic or whether im running A/C or not. I am measuring these temps via a OBD scan tool.

thanks

EthanS

Next time that I'm out cruising my 99 (likely Friday), I will trend my water temps via OBD and report back. This will be stop-and-go traffic in ~110F Phoenix weather. I've never paid close attention to this, but sounds interesting to see what everyone is getting.
My radiator, hoses, water pump, thermostat and coolant mixture are all about 10k miles old at this point.

saleenssc

Thanks. I look forward to your input and that of others.

My cooling system has about 15k miles on it currently.

lextout

WaveRunner

The temp gauge needle on my 98 reads above center but I suspect it is a gauge cluster issue as the gas gauge also has issues.

spuds

My 98 rides dead center on line 3.it gets as high as 1/8th inch above that when motor fan is kicked in on hot days,hard use.This web pic shows just about where Im at (Just a smidgen higher) going uphill on a hot day,otherwise I ride smack on that line

Stroock639

mine is always just below the middle with the needle basically just resting on the white tick mark

VortecCPI

Needle was always dead center. Mine got for a while hot and it had to be burped to remove air. Once that was done all was well...

EthanS

I ended up taking mine out Friday evening. Sun was down, but the dashboard temp was still reading 98F.
Water temp read ~189F around town, ~194F when cruising on the highway. Needle stays dead center on the middle tick always.

saleenssc

Thanks So much. I was looking for actual temps like you provided. i will have to look into why my temps are a bit higher than yours. I need to correct my earlier statement. My OBD measured temps are actually between 190 - 203 degrees. Again depending on certain conditions ( outside temps in the 90's and A/C on/off during stop-n-go traffic)

spuds

search engine coolant temperature sensor.They are dirt cheap and they go bad giving car false temp readings.

Michael88

I just had this issue in my 1998 LS400. Took it to the dealer and found out that the communication box was sending overheating signals to the gauge. The car was not overheating. It didn't even ping or pop like a hot block would. I could even place my hand on the block and not get instantly scalded. They measured the temps by three methods and confirmed that car was not overheating. Diagnosis false gauge readings. So before, spending lots of cash on radiators, sensors, water pumps, and such. Make sure the gauge is reading properly. This is a common issue.

timmy0tool

iTrader: (7)

there are two coolant temp sensors, one for the gauge and one for the ECU. make sure you replace the right one, if replacing!
the one for the ECU is the one that affects your MPGs.
https://www.clublexus.com/forums/ls-...ange-pics.html
https://www.clublexus.com/forums/ls-...read-this.html

and the temp gauge should not be right in the middle. my car's needle always rested below middle at operating temp (just like the picture above).

Michael88

I asked the Lexus dealer mechanic about two temperature sensors on my 1998 and he said there is only one. I questioned him if he is sure, because the forum said there are two, and he showed me the service wiring diagram and confidently confirmed only one on a 98. What years have two?

Michael88

Yeah those links aren't of a 1998. The engine looks different.