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Discussion Starter #1
Hi all

Got a new temp sensor for my alfa 166,is it simply unplugging the old one and screw the new one in or is more complicated than that ,

thanks already
 

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I believe it screws into the side of the thermostat housing, which is bolted to rhs of the engine. Don't think you'll have much trouble. But, if you're changing it due to having an error code of P0115 it'll more likely be the thermostat and not the sensor.
 

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Discussion Starter #3
I believe it screws into the side of the thermostat housing, which is bolted to rhs of the engine. Don't think you'll have much trouble. But, if you're changing it due to having an error code of P0115 it'll more likely be the thermostat and not the sensor.
Thanks, I have replaced it now,I did replace the thermostat 2 month ago and new radiator too.
My problem is this: After driving around 30 miles the temp warning light comes on ,water not leaking but seems a lot of pressure builds up in water system.
In town got no problem its only happens when driving in motorway
still not sure where the problem is
 

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Hmm I'm not sure then. Does the temperature go right up as well as the warning light coming on? It is of course a pressurised cooling system.. If it's getting very hot though the pressure will be greater. Has it only done it recently or have you changed the radiator etc to try to fix it? Don't forget that if you have a failing head gasket between a cylinder and the water jacket, that will pressurize the cooling system. Is it losing water at all? If the water smells of exhaust gas then it could be head gasket. You might want to try bleeding the system again in case you have a big air lock somewhere. There's a bleed valve on the top left corner of the radiator which is good to use as it's higher than the water jacket in the engine. I can't imagine why it would be worse on the motorway though to around town. Only other thing could be water pump vanes are no longer attached to the water pump. Can't think of a good way to test that though without taking it off...
 

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Hmm I'm not sure then. Does the temperature go right up as well as the warning light coming on? It is of course a pressurised cooling system.. If it's getting very hot though the pressure will be greater. Has it only done it recently or have you changed the radiator etc to try to fix it? Don't forget that if you have a failing head gasket between a cylinder and the water jacket, that will pressurize the cooling system. Is it losing water at all? If the water smells of exhaust gas then it could be head gasket. You might want to try bleeding the system again in case you have a big air lock somewhere. There's a bleed valve on the top left corner of the radiator which is good to use as it's higher than the water jacket in the engine. I can't imagine why it would be worse on the motorway though to around town. Only other thing could be water pump vanes are no longer attached to the water pump. Can't think of a good way to test that though without taking it off...
This has happened to two of my 166s. Motorway driving showed overheating. One was the water pump. On the other was the radiator full of "shttp://www.alfaowner.com/Forum/images/smilies/censored.giffft". Cleaned the radiator out and it was fine afterwards.
 

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Discussion Starter #6
Hmm I'm not sure then. Does the temperature go right up as well as the warning light coming on? It is of course a pressurised cooling system.. If it's getting very hot though the pressure will be greater. Has it only done it recently or have you changed the radiator etc to try to fix it? Don't forget that if you have a failing head gasket between a cylinder and the water jacket, that will pressurize the cooling system. Is it losing water at all? If the water smells of exhaust gas then it could be head gasket. You might want to try bleeding the system again in case you have a big air lock somewhere. There's a bleed valve on the top left corner of the radiator which is good to use as it's higher than the water jacket in the engine. I can't imagine why it would be worse on the motorway though to around town. Only other thing could be water pump vanes are no longer attached to the water pump. Can't think of a good way to test that though without taking it off...
Thank you for all info, Still have the same problem after replacing the Sensor :depressed:

I think bleeding is the next option , first i have to look for the bleed valve like you mentioned as i never done it before,I personally think i have some sort of blockage cause sometimes when the temp rises and red warning light comes on suddenly the temp goes back to Normal ( 90 degree )and then have no problem for the rest of the journey .

The car performance is excellent with no other problem other than this . oh by the way when car goes up hill it occurs ( 80% ) of the time :paranoid::paranoid:
 

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Discussion Starter #7
This has happened to two of my 166s. Motorway driving showed overheating. One was the water pump. On the other was the radiator full of "shttp://www.alfaowner.com/Forum/images/smilies/censored.giffft". Cleaned the radiator out and it was fine afterwards.

The radiator is new although not real Alfas
Always after taking the cap off and releasing the pressure ( taken care of course ) the car responding as normal
for the rest of the journey which is around 30-40 miles
 

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Well I replaced my thermostat yesterday. To bleed it all afterwards I filled the expansion tank with the bleed valve on the top left of the radiator open till water came out. Closed valve and ran engine up to temperature with the expansion tank cap off. Air and bubbles found their way to the expansion tank. Opened valve on radiator again to let more air out, then closed it. Opened bleed valve on the top of the one of the two hoses that go into the bulkhead to the heater matrix till water came out. Topped up expansion tank, put cap on and it's done. Mine is an aftermarket radiator too but it seemed well made.

I'd try doing the above first. It could be your new thermostat sticking closed perhaps? When it overheats on the motorway, try and see if the hose too the radiator from the thermostat, and the radiator itself is hot or cold. If it's cold, then thermostat isn't opening, or water pump is not pumping. If it keeps filling up with air locks then it's gonna be a fried head gasket unfortunately...
 
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