156 GTA Temp Gauge Puzzle - Alfa Romeo Forum
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(Post Link) post #1 of 12 Old 03-07-19 Thread Starter
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156 GTA Temp Gauge Puzzle

Hi chaps.
Question for you all regarding the running temp of a 156 GTA.
The gauge seems to read about 78ish when driving at motorway speeds (or even 40+ mph)
It sits at 90 whilst doodling along at 10 to 20ish
And, if stuck in traffic, it goes up to 95ish, fans cut in and it cools again to 90...... This behaviour is usually a sticky thermostat.


So I got the thermostat changed at the last service along with belts and all sorts. and there was no change.
After a while I decided that perhaps it was a dodgy thermostat that had been fitted, so I ordered a new one from Alfa Workshop along with a temp sender (the sensor in the thermostat housing) and a radiator as mine was starting to weep and new hoses and coolant.
After much skinned knuckles and snapped rusty bolts, the car now has new thermostat, temp sender, radiator, hoses, coolant, expansion tank, expansion tank cap and all was successfully bled...... and guess what? It still sits at 78ish on the motorway, yet sits at 90 when driving slowly.

Can anyone else confirm that this is normal for the GTA or do I need to look at changing something else? I can't see it being the gauge in the dash, as it reads 90 and fan cut in and out temps correctly.
Attached is a photo of it sat at 60 mph.
(post cleaning photos also attached for your viewing pleasure.)
Attached Images
File Type: jpg 156_TempGauge.jpg (58.8 KB, 31 views)
File Type: jpg GTA_1.jpg (197.3 KB, 28 views)
File Type: jpg GTA_2.jpg (182.5 KB, 32 views)
File Type: jpg GTA_3.jpg (124.7 KB, 21 views)
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It's normal. temp gauge in my 156 GTA ( also blue ) is behaving exactly the same way as yours.


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Yep. My 156GTA does the same. I was also puzzled by this when comparing it to my old GT V6 which would sit at 90 and not budge regardless of driving on freeway or traffic.
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Sounds normal to me …..
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(Post Link) post #5 of 12 Old 03-07-19 Thread Starter
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Originally Posted by 156GTASW View Post
Sounds normal to me …..
OK... so if all 156 GTA drivers find their cars sit at 78ish on the motorway but GT owners (and 147GTA) find it stays at 90 on the motorway, and they share the same engine and thermostats etc, then it can only be down to either the Gauge (which I rule out as it shows 90 OK and the fan cut temps OK), the ECU sending the data to the gauge (not sure why this would be the case) or the design of the front of the car. Perhaps the shape of the grill/openings on the 156 GTA channel air direct onto the thermostat housing/temp sender area and cool it just enough to register a lower temperature of the water in that region? If the stat is closed at that time, then there would be a localised area of water not moving just in the stat housing.
Either way, as long as 78degrees does not mean I am running on a warmup map that is affecting fuelling etc, then I won't worry. I realise that the rest of the engine will be nice and warm regardless.
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Originally Posted by alfatom View Post
OK... so if all 156 GTA drivers find their cars sit at 78ish on the motorway but GT owners (and 147GTA) find it stays at 90 on the motorway, and they share the same engine and thermostats etc, then it can only be down to either the Gauge (which I rule out as it shows 90 OK and the fan cut temps OK), the ECU sending the data to the gauge (not sure why this would be the case) or the design of the front of the car. Perhaps the shape of the grill/openings on the 156 GTA channel air direct onto the thermostat housing/temp sender area and cool it just enough to register a lower temperature of the water in that region? If the stat is closed at that time, then there would be a localised area of water not moving just in the stat housing.
Either way, as long as 78degrees does not mean I am running on a warmup map that is affecting fuelling etc, then I won't worry. I realise that the rest of the engine will be nice and warm regardless.
The 147/GT ECU/Body computer/temperature gauge works differently from the 156 set up. Essentially the 156 gives a live reading whilst the 147/GT is set up to stay steady at 90*C between a fairly wide temperature band. In addition the line on the 156 gauge (which isn't marked with a temperature) is 80*C and not 70*C so it looks like the picture in the OP is showing around 85*C on the gauge which would be correct. Should be easy enough to check with MultiEcuScan.
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Ignore the gauge, connect to diagnosis machine and read your temperatures from there via the engine ECU. Gauges on the 156 have never been the most linear or accurate.
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Quote:
Originally Posted by alfatom View Post
OK... so if all 156 GTA drivers find their cars sit at 78ish on the motorway but GT owners (and 147GTA) find it stays at 90 on the motorway, and they share the same engine and thermostats etc, then it can only be down to either the Gauge (which I rule out as it shows 90 OK and the fan cut temps OK), the ECU sending the data to the gauge (not sure why this would be the case) or the design of the front of the car. Perhaps the shape of the grill/openings on the 156 GTA channel air direct onto the thermostat housing/temp sender area and cool it just enough to register a lower temperature of the water in that region? If the stat is closed at that time, then there would be a localised area of water not moving just in the stat housing.
Either way, as long as 78degrees does not mean I am running on a warmup map that is affecting fuelling etc, then I won't worry. I realise that the rest of the engine will be nice and warm regardless.
156 GTA gauge is not ECU driven, it uses a different temp sensor to the 147/GT, the 156 GTA one is dual circuit, one circuit for the gauge and one circuit for the ECU. Quality of the wiring connector and earths can play havoc with the gauge readings.
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My 156 GTA originally did not exhibit those symptoms, but as it aged it did run hotter when moving slowly or when using a lot of power going at a moderate speed up a mountain road, for example.

Turns out it was down to corroded fins on the radiator stopping a decent air flow even when the fans were running at full speed.

I had to fit a replacement radiator. If I recall the first radiators had aluminium fins which didn't like salt and the replacement was copper which lasted longer. I ran the car for 13 years and 170,000 miles.

I never needed to replace the thermostat, but I did change the water pump for a metal rather than plastic one at the first cam belt change.

Andy
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Quote:
Originally Posted by Andy Bowden View Post
...
I had to fit a replacement radiator. If I recall the first radiators had aluminium fins which didn't like salt and the replacement was copper which lasted longer. I ran the car for 13 years and 170,000 miles.
...
Andy
I could be wrong, but I think it was the reverse.... Original was copper, and replacement aluminium ....
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here also new alu radiator and new thermostat installed, and still measuring 78 degrees on highway, 90 when on B-roads and in traffic.
(both on the gauge as well as OBD reader)

Quote:
Originally Posted by SHU159 View Post
Yep. My 156GTA does the same. I was also puzzled by this when comparing it to my old GT V6 which would sit at 90 and not budge regardless of driving on freeway or traffic.
From memory i thought the GTA also showed 90 when on the highway, but my mechanic confirms 70-ish is OK.
So the money spent on the thermostat was wasted...
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(Post Link) post #12 of 12 Old 3 Weeks Ago
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Originally Posted by ArieB View Post
here also new alu radiator and new thermostat installed, and still measuring 78 degrees on highway, 90 when on B-roads and in traffic.
(both on the gauge as well as OBD reader)



From memory i thought the GTA also showed 90 when on the highway, but my mechanic confirms 70-ish is OK.
So the money spent on the thermostat was wasted...
I've hooked up the OBD2 reader to Torque App just to confirm the difference and the 156GTA temp gauge is definitely off.
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