KC98LS

Hi all,

Today I drove my car to work today, 30+ miles. Took afternoon lunch break with no issues. Then at 5PM I started engine and noted my coolant temp gauge was still roughly at 40%. It's pretty hot here in the midwest, but was cloudy this afternoon, so a bit cooler, so no reason it should still be that hot 4 hours later.

Within a few minutes my gauge moved up nearly two notches, nearly to the red zone. I pulled over, and connected my scan tool, it indicated everything was fine. Coolant temp was about 185F (85C). I checked hoses, and they didn't feel too hot. I drove home, closely watching the scan tool temp, and it never exceeded 210 during stop and go traffic, and was right at 180-185F on the highway. Pulled in garage and let it idle, and it stayed right at 185F. I even used my infrared thermometer, and neither top or bottom hose/thermostat housing exceeded 180F.


No weird smells, no smoke, no steam shooting out, no typical signs of overheating.
Do I have a bad gauge/cluster, or just a bad coolant temp sensor? Is it easy to replace? I know the engine/gauge sensors are separate. It almost seems like the gauge was confused, and 50% now equals 0%, as it rose precisely two notches, and typically sits at half (two notches from zero)



Thanks!

Moarpower

Not everyone knows what step to take first in diagnosing or replacing parts. Some times a person might just want other opinions before throwing parts in. I really don't think you stating that you dont understand his thinking is worth taking the time to type nor is it helpful to the op.

As for the op it can only be a few things. Sensor is the first thing. If the Guage isn't dropping back down all the way when you switch off the ignition it could be something else.

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Htony

It sounds like blaming wall thermostat when furnace does not work. Wonder Op ever flushed cooling system on his car.

99LSprobs

Losiracer2

you need to rebleed your system, properly. You either have a ton of air trapped in it, or you're about a half gallon low on coolant. I experienced this after replacing upper and lower radiator hoses and discovered I was almost 3/4 of a gallon low on coolant.

refer to that sticker on your coolant overflow reservoir for the proper bleeding procedure.

KC98LS

Hi all,


Thanks for the responses! I did change the thermostat this winter, and tried my best to get any air out of system. I also pulled coolant hose off when I was doing alternator/power steering pump, but tried to bleed air out. I find it strange that it's been fine for months, and then randomly started acting funny.

I let the car sit overnight, and checked it today. Gauge was in between bottom and first notch.. very odd. Gauge does drop all the way to 0 when key is turned off though.

Can someone please point me in the right direction as to where the coolant temp sensor is located? I can't find it.. Also part number? I will try bleeding air out again tomorrow, hopefully that's all it is. Reservoir is currently full, but who knows..

Yamae

Since your actual measurements by the OBD-II port and the infra-red were OK, and the results simply mean that the ECT is OK and the engine is working properly. The problem is probably caused by the temp gauge itself or the related circuits.

Is the fuel gauge working OK?
The reason why I ask this is that when the temp gauge goes wrong, the fuel gauge often goes wrong. These are caused by the failing voltage regulator in the cluster unit. If both gauges are not OK, I can give you a way to troubleshoot more but you need to be OK to deal with circuit boards. An oscilloscope is needed too.

KC98LS

Fuel gauge is working normally.

I also put car on ramps, and ran engine for 10 mins with reservoir cap off, and 5 minutes at 2000 RPM with reservoir cap off. It made no difference, so I doubt air is my issue. Also unplugged battery for 15 minutes, and no difference.

Edit: Is there a additional temp sender for the gauge separate from the ECT?

Michael88

This is exactly what is happening in my 98. I made a post about 6 weeks ago. Took it to the dealer, and they confirmed the temps are at 180 - 185, burped the coolant by jacking the front of the car up when filling, and said it was a faulty "communication box" between the sensor and the gauge. I changed the coolant temperature sensor on the intake and coolant came out from the hole, so no air bubble there. Still have a false temperature gauge reading. It's the "com. box." They are year, make, model, and options specific, so nearly impossible to find a replacement.

Michael88

Curiously, are you getting any intermittently unpredictable no start situations?

KC98LS

I think I may have glanced at your thread.. Uh oh, so might cost $$$ to fix?! Did they give any part numbers for that? What about locations of that "communication box" ?

Nope, none whatsoever. Car runs absolutely flawlessly.

Michael88

Looking at the paperwork now. The mechanic called it a communication box and the diagram labels it a "combination meter." So the path is engine coolant temperature sensor ---> engine control module --- > combination meter ------> temperature gauge in the dash. Please correct me Yamae if I am wrong. My mechanic didn't even suggest trying to replace the "combination meter", because of the difficulty in finding it. He did however, suggest changing the engine coolant temperature sensor part number 89422-30030. I did and the temperature gauge didn't change much.

KC98LS

This site makes it sound like the combination meter is the gauge cluster/is part of the gauge cluster? Perhaps we could send our clusters to someone to fix?

http://www.lexls.com/tutorials/elect...ntcluster.html

Yamae

The combination meter means the gauge cluster. The water temp gauge is consisting of a drive circuit and a gauge which has 2 separate coils inside. Those coil's resistance should be like this below. As far as I have experienced, most gauge failures were caused by the failed drive circuit. It needs some skills and equipments to fix the circuit.

KC98LS

Awesome! Sounds like the fix is possible! But probably requires expertise.. Will probably cost $$$ to rebuilder?