I temporarily ran ground wire from engine back to cluster , drove around and it was reading the same.

After driving home from work for about 15 mins

Top hose 190 F
Bottom 176 F (at this time gauge is reading 6/10)

When I idle for 5 mins thereafter..the top hose may go up to 194 and fans come on. ( Gauge reading goes upto 8/10 and then drops down to 6/10)

I shot the base of the sender where it screws into coolant manifold and it was around 180F.

I strongly suspect there is a problem with my reading. It seems it is amplifying the problem little too much.

 

Running out of things to check.

The gauge receives battery voltage at the terminal that does not go to a wire connection. Make sure the voltage at this terminal is battery voltage.

Might run a wire direct from gauge sender wire connection to sender to bypass car wiring.

 

This morning the top hose was showing 170F/bottom 100F(t-stat no open yet)after driving for 15 mins , but gauge showed 6/10. There is no way the gauge should indicate 6/10. correct?

Also on a normal running engine, the gauge don't read past half way mark yet we know fans come on and off before that. It seems to me the problem is with reading?

 

If it is the reading then your options are known.

You have two gauge clusters, the odds of both being bad are low. If both have the same strange readings then the issue may be some place else. This leaves the sender and wiring.

You can bypass the wiring. Plus compare ohm readings of two senders you have in heating water. Then compare to your resister setup values that simulates the same gauge indications. And determine if one sender output is wrong.

Plus check for battery voltage at the gauge terminal that is not ground or going to the sender.

 

Thanks Toyo for your time. The problem is resolved after I replaced the sender with OEM. Erratic gauge operation made me skeptical on just about everything.

 

Thanks for posting back with the fix. Would state uncommon for aftermarket sender to cause problems requiring OEM.

 

Hi guys! toyomoho and jaggudada. I have read all of the comments and am having the same issues. I have replaced the radiator, water pump , thermostat (twice) all 3 temp sensors, and actually did the head gasket and water pump (again)...still reading at about 3/4 on the gauge. I have no way of doing all the testing that you two did (99% of it was above my head!). I am going to re-do the temp sender with OEM and pray. I have googled for untold hours about this and thought I was going to go crazy! Lots of people have had the problem, but no one has gone as far as you two!! Most folks don't respond back with either that they fixed it or took a hammer to it! LOL

 

What year of car and engine type V-6 or 4-cylinder?

Are you doing this work yourself or a shop?

Is the temp needle position solid once the engine is warmed up or does it move around?

First determine if there really is a problem with the coolant temp.

Obtain a thermometer. A good one would be one having a remote sensor wired to a digital readout. Can be purchased for around $10. Any thermometer will do but needs to display in single degree units.

Engine cold, remove radiator cap and install the thermometer into the radiator fill port. Make sure the radiator is full of coolant. The level should be slightly below the filler neck.

Let the engine warm up. The coolant should reach a max of about 199-203F before the radiator fans start up. The coolant should stay at a set temp as the fans and thermostat will operate to do so..

When the engine is heating up, note the position of the temp gauge needle and compare to the coolant temp via the thermometer.

You want to determine if the gauge is the problem or the engine.

Don't put your head/face over the radiator fill port when reading the thermometer! Its unlikely but the hot coolant could burp out of the radiator. Wear safety glasses.

 

It is 4cyl 2.2 1999 toyota camry. It all started with a massive crack in the top of the radiator in August..in Central Texas! I limped to a shop (luckily not too far, maybe a mile or so, considering I was on the outskirts of Austin). They replaced the thermostat and radiator. Everything seemed fine. Then,(approx 5 days later) there was a problem with the belt squeeling (had replaced water pump about 6 months prior, at that time they said they did the pump, belt, tensioner and pulley (they certainly charged me for it).)Had belt adjusted. one week later, belt shredded! Towed back , replaced belt. Then, the fun began!
The gauge has always sat at dead middle. It has never moved one iota (except when the radiator busted, of course). My last Toyota Camry was exactly the same. All of a sudden, it would rise to 3/4 for a short drive. It warms up at a natural normal time-frame, then hits 3/4. Upon driving to one of my jobs (outskirts of town) , it rises a little more (not quite to the red), but will go back down to 3/4.. This certainly got my attention.
I , personally, replaced the 3 sensors (fan switch, ect sensor, and temp sender). All aftermarket. It didn't help with the issue, but it seemed to be a quick, easy , something-I-can-do attempt. At this point, I saw white smoke out of the tailpipe while I was waiting for it to kick the fans on.. Still August, easily 100 degrees out. Not good!! Took it back to the shop that did the radiator and they replace the thermostat with OEM. It still continued with the same readings. He had it for several days, but could not find why. He did take me for a ride with an in car computer that showed that fans were coming on properly, coolant temp was not hotter than it should be (I don't have the temps showed at that time with me right now, I am out of town). Temps were normal, even though the gauge showed 3/4. He did replace a crank position sensor to the tune of $500, that I was not wanting, but he wouldn't look at the car without doing it. I had no check engine light, but he said it was "in the computer". I just wanted the damn thing fixed! On the ride along, I saw the temps with my very own eyes and they weren't above "normal". He said maybe my temp gauge was "my new normal" and maybe it was the instrument cluster. It is not overheating, per se, just the gauge. Well, the white smoke still concerned me. But I wanted my car outta that place! He also mentioned that I needed a new tensioner and pulley, but he knew I was SO done with them. One of the guys there spoke to me like I was an ignorant woman, and not much pisses me off more than that! Even if I don't know something, I don't like to hear it that particular way.
Luckily, I have an "in" with Austin Community College here that has Automotive Technology classes. They replaced the head gasket. They also replaced water pump, belt , tension and pulley (I supplied all parts). To the tune of a whopping $45. The instructors are all master mechanics and I have had them do many things for my car and truck, with no issues ever. I was not able to speak to the instructor , he left for vacation the day after they finished my car.
Now, is when I began my search again and came across y'alls posts. I am more than willing to try replacing that sensor with OEM.. A relatively inexpensive try that I can do myself.
I am going to double check first that it was properly bled for air. I can honestly seeing the college maybe not giving it long enough to do it properly.. I have seen estimates (after much research!) of it taking 30 minutes or more. But, I also saw a post with a link that said this engine was "self-bleeding". (I don't believe that though, call me skeptical!). Only an owner would do that for that amount of time!
I am still going to get a therm, though, even though I saw the previous reading on the in -car computer..
I just can't think of what else it could be!
Thank you so much for your response!

 

Well, I wouldn't have believed it, but the new OEM temp-gauge sender fixed it! I did borrow a little radar type temp gun and watched hoses, coolant , and everything else I could point the laser at while I burped it (before I replaced the sensor). No change in gauge at all. But, hey, worth a try! After all of the things replaced (some twice), this did it!! After all these months, my little car is back to normal..I think I might take a little trip to celebrate , now that I feel confident in it. I hope this helps someone else in the future.