Whats the actual temp?
Fan comes on automatically as temp rises, it's normal. About 192F on most.

 

Whats the actual temp?
Fan comes on automatically as temp rises, it's normal. About 192F on most

Yellow-normal
Blue- fan starts
In the second corolla with the same engine, it stands in the middle.
So it probably shouldn't be like that?

do you have one of those instruments to plug into the cars computer that can give an accurate temp reading

I need to buy an OBD2 adapter..

 

Usually the gauge will stay right near the middle of the scale, and doesn't move, once the engine is warmed up. That's the way both of my 7th gens were/are, and seems to be the experience of most here.

Where all does your gauge indicate after warm-up?

 

do you have one of those instruments to plug into the cars computer that can give an accurate temp reading

 

If this particular Corolla is OBD2, you will be able to read the temperature with a scanner or code reader plugged in, which is worth checking if you have the equipment. I have a Bluetooth OBD2 dongle, and my phone.
There are also those temperature gun things, but I don't know anyone who has one.
The best way to monitor it is with a mechanical gauge which actually samples the coolant.

But yes, I'd say that there's a problem there, but I'd still want to be sure that the temperature readings are accurate. You can smell it when the engine is hotter than normal. Maybe the rad is a little clogged?

 

The radiator fan should come on before you even notice the needle moving above normal. I'm more inclined to think the fan isn't coming on at the proper temperature. Is the radiator fan switch an original Toyota part?

And what brand is the new thermostat?

And do you have a reasonable mixture of coolant and water around 50/50?

 

Is the radiator fan switch an original Toyota part?

And what brand is the new thermostat?

And do you have a reasonable mixture of coolant and water around 50/50?

Radiator fan switch is probably original.
I'd have to take it out to be sure..
Thermostat is from Toyota, original.
I always buy ready-made coolant.

After you replaced the thermostat did you bleed all the air out? If there's maybe a small amount leftover it could cause a mild overheat

Yes, there is no air in the system.

 

After you replaced the thermostat did you bleed all the air out? If there's maybe a small amount leftover it could cause a mild overheat.

 

Have you tried swapping your fan relay?

 

Yes, that was the first thing I did.

 

The temp gauge, primary fan switch, and ECT for the computer are all pretty independent systems as far as I know, so now I'm thinking that the car really is running warmer. But how much warmer? I think I'd still want to know the actual temperatures of the engine before spending money and time on it. Because the fluctuation might just be five or ten degrees - but if it's already running at the top of the normal range, then there's a problem.

My '97 runs just a hair above the middle, and never moves perceptibly once warmed up, and it still has its Harrison radiator which I presume to be original. My old '93 was the same way.

 

BTW, You guys are great for your quick replies.
I will buy an adapter and check the exact temperature that the scanner shows.
Anyway, I was gonna buy it.

 

If you're gonna buy an OBD2 Bluetooth dongle, don't get the cheap clear blue one.

 

I can not find Bluetooth dongle, just this:

I would prefer bluetooth but I have a scanner so I can do it.
Can you show me yours? Or some store where I can buy.

 

It sounds like it will be hard for you to easily read the coolant temperature without the OBD2 port. I was able to read the temperature the computer sees with my OBD2 reader 4.5 years ago and made some notes about the radiator fan.

"Radiator fan on 5 sec after reaching 196F. Runs for 20 seconds. 20 seconds after it turns off temp drops to 189F. Temps read by OBD-II"

At 196°F (= 91°C) you should barely see the needle above normal near the middle.

 

I will order an adapter, when it happens, I will immediately connect it to the scanner and see what I can find interesting there.I will compare the results with yours. Thanks.

 

My thought is this, your cooling hose(s) may have a pin sized hole. Feel your cooling hoses for a collapsed hose. ECT may be faulty also.

I suggest looking into silicone cooling hose kit to remedy this.

 

Mine sits just below the middle, and does move down a tiny bit after extended periods of engine braking (more than a minute continuous), but it’s very very little it moves, barely noticeable.

 

The gauge shouldn’t move once at operating temperature. The OBD2 readings will probably confirm the gauge’s readings. You should double check for air in the system.

 

Highly doubt a Euro-market 1993 model is going to be OBD2...

 

most likely when u replaced the thermostat, the air get into the coolant system, u need to bleed out the air. the process is pretty simple. park ur car on uphill platform ( or put the front on jack stand), get one of those big funnel, put some electrical tape around it to make it fit the radiator neck, make sure it's air tie so air can't get in and coolant won't leak out. now, turn on ur engine, turn the heat to all the way to hot but turn the fan to just minimal. watch ur engine warming up till the fans start running, u will see air bubble coming up to the surface, fill the rad will coolant if u start running low, keep watching when the fan start running, until u see there is no more air bubble coming up then ur system is good to go. take the car for a ride, keep an eye on the temp. park ur car. wait till the next morning then check ur coolant reservoir to see if it's empty, fill the reservoir if needed.

 

Today I picked up the adapter, tomorrow I will try to connect and give you the readings.

 

i bought one of those , hooked up to my 90 corolla coupe years ago, and it didn't read any code . it doesn't seem to connect to the ecu at all.

 

The only thing I can get from my OBD1 -> OBD2 adapter is DTCs. No live data. I doubt temp reading (live data) is exposed through OBD1 but I'm happy to be proven wrong.

If there's truly no air (are you absolutely sure you've bled it sufficiently??) - another possibility is broken impeller on the water pump.

 

Why can't you go to Harbor Freight and buy a temp scanner and scan it when it reaches operating temp. No muss no fuss. I have one and it works great.

 

On post #26 mjneiner has it right. A 'laser pointer' thermometer can tell you a lot, you need direct measurements from an independent tool. Just put the red dot on the aluminum radiator (low middle and top) and the thermostat housing and you will know if you are overheating. Taking equivalent readings on another car (as a frame of reference) will give you the baseline on how these parts should read. $12-25 dollars on Amazon or Harbor freight.

 

Old school. Unplug the sensor, measure the resistance hot and cold. Find the chart that lists temp:resistance for that sensor.

 

Good and bad news.
Got a used sensor. I changed it and noticed small changes. Better changes, but still something is wrong with the gauge.
But there is a change so that was a good lead.
To the point.
The new sensor shows like this:

When driving, it is lower by 1-2mm.
The fan starts:

Is the used sensor showing a wrong indication?
I wonder if it would be different with the new original?

I have failed to connect to the scanner.

 

As long as it’s under the midpoint. What you want is the coolant temp to not rise while in motion or stationary. I don’t think you have any issues.