Hello guys,
two weeks ago I did my timing belt, water pump, oil and coolant maintenance.

By mistake I didn't followed the procedure and didn't put the fan on hot and open the block coolant bolt. I removed the bottom radiator hose and removed all the coolant.

After doing all the maintenance I put coolant again(Note the car was raised from the front so the top of the radiator cap was higher than normally)

And after bleeding it following the same procedure I always used in any car(running the car with the heater on so coolant can flow into the radiator) I went to test it.

The temp gauge always used to be in the center and never moved not even by a milimeter.

Now it sometimes oscilates and half a minute later is in a different position.

I though it might be a problem with a buble of air so I had the car runing with the radiator cap open for like 20 minutes, and there where some bubles of air that where removed but although situation has improved it still oscillates.

Any idea on how to fix it.

The green line is where it used to be and the red ones are the areas between oscilations now.

The car is an 98' Honda Civic EK3 Euro.

It has a D15Z6 engine.

 

Your picture is pretty small but it looks like the needle is still around proper ECT. I don't think it should be a problem as long as you aren't deviating too far from the center (proper ECT).

I installed a mishimoto radiator/shroud and replaced my thermostat on my civic, and now my temp gauge reads a little higher ECT once the engine is warmed up than before.

I've heard the OEM analog ECT sensor's aren't extremely accurate. I would suggest installing a digital autometer one if you want to make sure the engine doesn't have any irregular overheating.

 

I think this picture would give a better idea.
Where within the temp gauge should the fan kick on? And where is a dangerous overheating temperature as we don't have number on the gauge it is difficult to measure it.

 

Add car and engine information to your first post.

I think there's still air in the system.

 

Added.

Would it be worth to remove the coolant again following the manual instructions and do the process again or can I get rid of those last bubbles without having to do that.

 

I think draining the coolant would be excessive.

When you were bleeding with the heater on MAX, was hot air blowing from the vents?

Did you have the front end raised?

Does your engine have a coolant bleeder valve?

 

Yes, I was getting hot air and the fans where in the maximum position.

No, I didn't have it raised when I tried to bleed it. Only when I put the coolant the first time.

No it doesn't have a bleeder valve.

 

Could be the brand/type or the mixture ratio (water/coolant) that you used.
Also, possible that the thermostat is not opening completely.

 

That wouldn't make much sense.
I mean the coolant is for -27C which probably is a lot lower ratio than previously used, but that would only explain a different measure but not the oscillation of the gauge.

The thermostat opens sucesfully because at one point the car is almost warm up and then temp sudenly drops as the thermostat opens and cold coolant enters in the circuit.

I am going to extremely raise the car this weekend so the front is really hight and try to bleed it again.

 

Might be the engine coolant temp sensor. After you drained the fluid maybe some gunk collected on the sensor. Easy to take out and inspect maybe replace it if it is original.

 

Ok guys.

I've tried to bleed the system again. This time with a slope of more than 45 degrees.
I literally put the car on an offroad track and opened the radiator cap, reved the car to 7000 rpm for 1 minute and I still have the strange behaviour.

I will try removing the temperature sensors as I am not sure if it's really a pocket of air as the other systems(the fan work, the engine light doesn't come on) work as intended.

Any other ideas?