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[mkaminski100]

My Omega X20XEV warms up only up to 82 degrees! It never goes to 90 on the dashboard.  I thought that it’s a thermostat, so changed to Vernet. It got even worse (big temp drops, temp up to 80 degrees). Then bought MotoRad thermostat, got bit better, but even though, the temperature wont go over 82. Got an OpelScanner and checked – 82-83 in town, 82 on the run (checked from ECU sensor).  
Hoses are cold up to ca 80 degrees, and I think that there is no way for 3 thermosats to be broken the same way (all three are opening at ca 80 degrees).
I thought that it might be a sensor, but the ECU and dashboard indicator shows the same temp. Does it look like both are old and not showing proper temp or is it real temperature and theses something wrong?
I don’t have any idea on how to find what’s wrong so maybe you can help me.
I put a piece of cardboard and now it shows 90 degrees in town but it’s not the way to solve it.
I found the same in my second Omega 2.2 - it takes a lot of time to get it warm (heating pipes to oil filter and throttle body) and it keeps 82 degrees.

[Grumpy]

I assume you've checked that the Air Con fans in front of
the rad aren't on when they they shouldn't be, and that your
main fan behind the rad isn't coming on too early?

If either are operating incorrectly, you are looking at the
fan switches on the rad.

Edit:  Fan switches will only affect your main fan. Air Con fans will
be fault in the circuit.
Must get brain in gear next time.  

[mkaminski100]

Any fan isn’t on (I use ECO and checked that before). As far as I remember, engine cooling fan goes on when temp reaches ca 90 degrees. I know when the fan is on and the temp drop if far behind it so I think it’s not the fan that is cooling it. If the fan switch wound be broken, it would have any (or small) impact at the engine temp when on motorway.
This gives me an idea of both sensors showing lowered temp or any problem in the engine that pushes the thermostat to be open.
I will check when the engine fan is on and this will give me an idea what might be wrong (3 sensors cant be broken the same way)

[Matchless]

Bit of theory first....in normal operation...

The engine operating temperature is set by the thermostat and nothing else.
The thermostat will have an opening temperature (92c in your case) when it just lifts off its seat and allows a little cool water to flow from the radiator into the block.
If the temperature rises further, the thermostat opens slightly wider which allows more water to flow and provides more cooling.
At around 95c the thermostat will be fully open so cannot increase the water flow and we are in danger of losing control of the engine temp.

The radiator has a temp sensor about half-way down the core, if the temp at this point rises too far then we are close to the point when the thermostat loses regulation so we start one or more fans to bring the return temperature down. There is usually lots of hysteresis (10c or more) on the radiator sensor to prevent rapid on-off cycling of the fans.

If we apply this theory when fault finding then:

Engine temp too low
Excessive coolant flow. Caused by thermostat stuck open or wrong thermostat fitted. (opening temp too low)

Engine temp too high
Insufficient coolant flow. Caused by stuck thermostat, air locks, coolant passages blocked in radiator or engine or faulty coolant pump.
Insufficient radiator cooling. Caused by poor air flow, corrosion or scaling of radiator coolant passages or extreme air temperatures. Radiator air passages blocked or fans(s) not operating.
Excessive heat generation. Caused by hot combustion gasses in coolant (head gasket blown) or retarded ignition (Knock sensor or ECU fault).

[Matchless]

You have read both ECU and gauge sensors and both report 82ish so are likely to be correct.
You must have the wrong thermostat fitted. Its possible that the aftermarket thermostats are all based on a hot country spec, not the 92c opening specified for the UK/northern Europe.
Try a genuine VX stat.

[mkaminski100]

All three thermostats are set to 92 (checked on the thermostat valve). I bought one in UK, second in Poland. I am sure that Vernet (GM supplier) and MotoRad (USA) are fully closed at ca 78-82 (cold hoses).
When the engine is cold (outside temp 7) software shows 10 degrees (checked by OpelScanner) but it might get faultier when it's getting hot.
If the fan starts running before 90 degrees (will have to confirm that) it means that the sensors mounted on the engine are wrong.
I was told that there are 2 sensors at the back of the engine - one for the dashboard and one for ECU. Am I right?
Second thing might be a weak thermostat which is pushed to be open by a coolant flow. I found that when the engine gets warm (82) the temp drops instantly to ca 70 and then raise again. It looks like its open too wide.

[Matchless]

All three thermostats are set to 92 (checked on the thermostat valve). I bought one in UK, second in Poland. I am sure that Vernet (GM supplier) and MotoRad (USA) are fully closed at ca 78-82 (cold hoses).
When the engine is cold (outside temp 7) software shows 10 degrees (checked by OpelScanner) but it might get faultier when it's getting hot.
If the fan starts running before 90 degrees (will have to confirm that) it means that the sensors mounted on the engine are wrong.
I was told that there are 2 sensors at the back of the engine - one for the dashboard and one for ECU. Am I right?
Second thing might be a weak thermostat which is pushed to be open by a coolant flow. I found that when the engine gets warm (82) the temp drops instantly to ca 70 and then raise again. It looks like its open too wide.

Does the fan run at this point? If so it indicates a thermostat fully open and stuck......temp rises until fans cut-in then fans pull return temp very low...You shouldnt see much change in engine temp if the thermostat is working correctly.

Thought....BiFuel??   Is it original fit or aftermarket?....Has a coolant hose feeding the mixer been connected where it by-passes the thermostat??  ie from heater pipe to radiator rather than from heater back to block inlet?

[Jukeboxnut]

It is possible to test the opening temperature of the thermostat by the old method of placing it in a pan of water and heating it on a stove while noting the water temperature with a thermometer, at least you could prove that the thermostats are opening at the temperature marked on them.

There are indeed 2 sensors on the back of the cylinder head, one for the gauge (single wire) and one for the ECU (two wires).

[TheBoy]

What are the markings on the dash gauge.  Remember some are 90C - 100C with midpoint at 95C, whereas later cars are 80C - 100C with midpoint being 90C

[mkaminski100]

I will check when the fan starts, but as I remember, it starts around 90 on dash.
I tried to check one thermostat in the past, and it was working fine in the pan, but was opening too early. I don’t have any 100 degrees thermometer.
Mine is B FL so the midpoint is 90 degrees and it almost two lines below (80 something)
I will check when the fan starts and check the LPG connection ( I think that it joins pipes between the engine and aircon)

[mkaminski100]

So the fan starts at 90 degrees. It looks like the fan sensor is broken but when on the motorway temperature never reaches 85 so fan is not on so cant reduce the temperature. This means that the temp reaches 90 but there is a false reading at the dash board.
I will hev to check which sensor is OpelScanner using as one pin sensor might be broken. I wil disconnect is and find out if OS will give any temperature reading.