I've had an overheating issue with my 1996 ls400. To remedy I replaced the radiator, thermostat, waterpump, fan clutch, and drained coolant. It doesn't seem like my car burns any coolant. I'm really starting to think my gauge is faulty. my car has never actually overheated. The gauge just tends to rise driving up hills or underload.

It usually rises to the center from the 3rd white mark. Then if I really floor it it will rise higher than the center 3/4 of the way up sometimes. However I drove my car today to test it. After I got the needle to go over the center towards the 3/4 mark. I pulled over really quick and used a laser temp sensor to take the operating temp (right near the temp sensor) the highest it ever read was 199 degrees. But usually it was anywhere from 165-180. I'm a little lost and could use some guidance. I was hoping to drive this car for another 5 years.

I'm really hoping it's not a small head gasket leak...

Temperature after idling for 15 minutes and than holding 2500 RPM for 5 minutes. (To bleed system).

Temp starting to rise after gunning it up a hill

Temperature after needle rose above center, needle got close to 3/4 before I pulled over and shot the temp inside the engine bay.

 

Also here is a photo of oil on my dipstick.

Dip stick after driving for 20 minutes

Waterpump replaced. Along with main crank seal.

Old waterpump. Had some dried coolant marks near the week hole.

 

I'm not sure you have a problem. Dumb question here but did you replace your temperature sensor? I mean it might not make any difference but just wondering, maybe its your gauge possibly too. Most cars operate between 195-220 degrees. If its hot and your running up a grade on the highway its going to run warmer. Sounds like it isn't over-heating. I can't tell for sure but the oil looks okay to me. 165 is running way too cool, 180 is the bare minimum you want it to run, running too cool like that from my understanding can cause it to run too rich and you certainly don't want that at all.

If you want to do one test that could eliminate one possibility is test the coolant for exhaust gases. One tell-tale sign that say there is an issue is if you see bubbling in your coolant reservoir, that could could point towards super-heating your coolant from say a bad head gasket, or perhaps hairline crack possibly something like that. A head gasket can fail in different ways, one way is getting into the oil, another way is failing towards your coolant chambers to where it will not show up in the oil but causes super-heating the coolant itself. Ask me how I know, I also own a honda civic and my honda has that problem.

So these are things to consider and maybe look at in some manner. Hope that helps some.

 

So this afternoon I replaced my temp sensor. I can't remember if I replaced it when I bought the car 4 years ago. Anyways I am going to test drive it again tommorow. I have a feeling it's the gauge, wiring cluster or temp sensor. The reason I showed the 198 degree reading was to show it's within operating temp even though the gauge is above where it usually sits. Ever since I bought this car it had always stayed at third white mark.

Only other issue with the car is the AC is always on unless I pull the relay. Even if I switch the whole climate control to off the clutch is still engaged. The only time the clutch is not engaged is when I pull the relay.

 

Just to let everyone know, the problem ended up being the temperature sensor for the coolant gauge. I replaced it 4 years ago when I bought the car....😂 But decided why not replace it again. Completely fixed the problem. No more creeping coolant level. Sits dead center on the third white mark. No more stress about my car overheating. It was just a $13 sensor. After replacing the radiator, coolant, timing belt, water pump, thermostat and the fan. 🤘 Now my car will easily run over 200k. Probably to 500,000.

Next it's time to replace transmission fluid.

 

Glad that was an easy fix.

 

WHERE IS IT LOCATED?Is it the one by the passenger side where the plug wires run or the one on the bottom of the radiator.Same problem on my 95, I just bleed mine 3 times every summer

 

Part number? Is it the one on the radiator?

 

It's the sensor to the left of the thermostat housing, behind the left ignition module. Its a one pin connector. Usually the plug is gray in color. Don't have the part number handy.

 

The once close to the ECT sensor. To the left of the thermostat housing. Yes near the plug wires/ignition module.