fuzzygrape

For the past month or so, when fully warmed up my 98 LS400 has been showing the temp gauge at a little over the 3/4 mark up. It hasn't overheated or anything, and it runs great. It always goes to this one place right over the third tick mark, and never goes over.

I took it on Friday and the shop told me my thermostat is working fine, and that the engine is running at normal temp, so not to worry about it. They said that if I wanted to fix it I need to replace the coolant temperature sensor... they wanted to replace it then, but couldn't get the right part in or something.

Has anyone else had this problem? This was a new shop I've never been to before, and I'm a tad skeptical that this is the issue... they seemed to be in a bit of a hurry when they were looking at my car. I was thinking that my thermostat was dying on me, so I was surprised to hear that was okay. I thought that a bad sensor would trigger a CEL too... Anyhow, is this possibly causing any damage to my car, or just making my gauge not read correctly?

mspearl95

any chance you have air in the system? The first ls400(95) had listed in the service records a false overheat that was just due to an air bubble trapped in the coolant system, that cause the temp sensor to spike.

fuzzygrape

Hmm... interesting, haven't thought of that.

I'm considering taking it into the dealer to have a look. As much as I know I'll pay more vs. an independent shop, I just want to know for sure that it's not something with my cooling system and I've taken it to 2 shops so far that have just told me to "not worry about it".

mspearl95

dunno, i would worry about it. Have you checked out the front of your radiator to see how clogged up with crap the fins are? I could not BELIEVE how much stuff was stuck in mine.

Xaolin

my car was doing the same thing. but mine was clogged at the reservoir tank which is also where u add antifreeze. i flushed it and replaced the thermostat and the thermostat housing cause running it hot like that made a small pin hole. and when u flush it make sure u bleed it just in-case there's air pockets.

fuzzygrape

Just an update... It's the instrument cluster! Apparently my car is running at normal temp and the temp sensor/thermostat are functioning normally... But the gauge is climbing too high. Lexus wanted to charge me $600 to fix it so I passed!

Lavrishevo

iTrader: (1)

Are you sure it's not the sensor for the cluster and not the cluster itself? They main engine temp sensor and the one that controls the gauge are not the same.

fuzzygrape

Yup, apparently they determined that the sensor is working fine -- but the cluster itself is the issue.

kayuwong

93-94 LS400 is know for bad capacitor on the cluster. I believe 98 are catching the same issue as well.

Lavrishevo

iTrader: (1)

If you do want to fix the problem you can pull the cluster and send it to a shop to be repaired. I was quoted about $250 to fix the sticky needle problem.

DNA Speedometer's in Tampa.

BIPPUthis!

I have the same problem on my cluster. There are two sensors that drive the temp gauge. The ECT (engine coolant temperature) sensor...which is the sender, then there's the temperature gauge receiver...which is in the cluster itself. If you don't have any other cluster issues (e.g. rpm and speed sticky needle issue), you can replace the receiver but if you have other issues as well such as the sticky needles...you may want to send it for repair as stated above.

fuzzygrape

Unfortunately my speedometer gets stuck fairly often too, so I'm pretty confident the issue lies within the cluster. At the moment I'm debating whether or not to fix.

WaveRunner

I also have a 1998 with this similar issue. My temp gauge reads above middle but car runs fine for over a year. My RPM and MPH gauges get stuck when humid, a tap on the top of the dash frees them. Most annoying, my gas gauge is stuck at full and drops to middle when empty. The trip computer works and I've relied on that. Also, the low fuel light will appear when gas is low even though the gauge shows half full gas. I changed the gas tank sender in the tank but that changed nothing. I have concluded at this point the gauge cluster needs an overhaul. My gauge also doesn't have the blank setting for the trip computer which is rather annoying. It always shows some info. Although I swear I've seen 1998's with blank trip computers but I guess just not mine. Maybe I will upgrade to a refurbished 1999 or newer and have the seller reset the miles to match mine.

Rokas

I have a similar problem but my needle stays at the very bottom. When I changed the Engine Temperature Sender, it shot all the way up and gradually dropped back down. It's obviously my cluster but I wonder if it would show a rise in temp?

YODAONE

.....So we know dealers do not repair circuit boards, but routinely replace the entire assembly...radio, ECU, daah cluster, etc.

However, it appears no one is willing to spend the money..

There will reach a point when spares are no longer available and repair is the only option.

Rarely do all circuit board components fail simultaneously , so it is a trouble shooting process to identify failure item(s).

Perhaps someone familiar with circuits cares to sort out which component(s) have failed...and repair techniques...

Not all of us care to or are capable of working on circuit boards, however it is helpful to have information handy to conserve electronics tech time.