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 Posted: Wed May 01, 2013 8:12 am |
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Joined: May 01, 2013
Posts: 5
Trade Rating: 0
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Hi everyone 
I hope you can help.
I have a 2003 206SW with the 1,4 HDi enginge.
It runs fine, but the termostat sometimes fails to close -resulting in the engine being heavily cooled and water temperature drops fast to around 50 degreess.
The good thing is: The cooling system works great 
The bad thing: How do I locate the termostat? Is it easily accessible or hard to reach? Do I need to replace it or can I take it out and make it work?
Does anybody have some kind of exploded view of the engine or maybe a mechanics manual for it?
I hope you can help me out - thanks!
Best regards
Jens Christian - Denmark
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Posted: Wed May 01, 2013 2:06 pm |
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Joined: Feb 07, 2010
Posts: 2719
Trade Rating: +6
Location: UK
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If it fails to close it will just be taking longer to heat up? Wouldn't cause the temperature to suddenly drop.
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Posted: Wed May 01, 2013 2:35 pm |
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Joined: May 01, 2013
Posts: 5
Trade Rating: 0
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Hi Steve -thanks for your reply.
Let me try to explain the way it does:
Often the heating/cooling works with no problem and the temperature goes up to normal.
Then sometimes (now more and more often), suddenly the temperature drops to around 50 degrees. Some times it will go up again and go "up and down" in temperature. But moste often it will "hang" and stay way too cold. That is why I expect it to be the termostat that "hangs" open and therefore the cooling system is working full time = too cold engine running temperature.
If I pull over and stop the engine and start up again it will often go back to normal. Sometimes for the rest of the drive -sometimes for a little while.
I am not sure that it is the termostat -but it is the only thing that makes sence to me
Thanks again -I hope you and others can get me closer to the solution
Thanks.
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Posted: Wed May 01, 2013 2:45 pm |
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Joined: Feb 07, 2010
Posts: 2719
Trade Rating: +6
Location: UK
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Sounds like a sensor failure. The thermostat opens when the car is warmed up, to allow the water to travel to the radiator to cool and back around the engine. The cooling system is supposed to work full time. A diesel engine does run around 80, but if your needle is rising and dropping sounds like a sensor fault rather than the thermostat.
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Posted: Wed May 01, 2013 3:01 pm |
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Joined: May 01, 2013
Posts: 5
Trade Rating: 0
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Hi - you might be right.
I just think: The mechanical thermostat opens when the water is too hot. That is good. But if it gets "stuck" in the open state -then the water keeps flowing and cools the water/engine too much because the thermostat does not close properly again.
Wonder if a sensor failure would show on the computer as an error? Worth a try.
Thanks.
If others have the mechanics /engine exploded view etc. I would be happy too.
Best regards from Denmark
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Posted: Wed May 01, 2013 3:07 pm |
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Joined: Feb 07, 2010
Posts: 2719
Trade Rating: +6
Location: UK
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It can never cool to much, as the engine produces more heat than can the radiator can cool. Just google how a cooling system works.
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Posted: Thu May 02, 2013 4:50 pm |
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Joined: Aug 04, 2011
Posts: 1343
Trade Rating: 0
Location: Swindon
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If you are driving along at a steady speed the cooling system will cool too much if the thermostat is stuck open. If you are stuck in traffic then a thermostat stuck open won't give enough cooling until the fan cuts in.
However, it is relatively unusual for a thermostat to fail in the way you describe. What you have described is sometimes air in the system or, as Steve stated, a failing sensor.
The danger with air in the system is that the low temperature being shown by the gauge is at the time that the air is on the sensor and not the water. The sensor can't detect any heat because it is in air and shows a low temperature when what is possibly happening is the engine is starting to overheat. It is one thing I always remind my kids and that is if your temperature gauge suddenly reads low stop immediately and check that you haven't lost your coolant.
I don't rule out an intermittent sticking thermostat but I bet on air in the system or low coolant level first.
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| Morris 1000, Austin 1100, Escort Mk2, Fiat Mirafiori, Alfa 33, Alfa GT Junior, Alfasud, Alfetta GTV (2x), Alfa 164 3.0 V6, Alfa 164 2.0, Alfa 75 V6, Alfa 156 2.4 (diesel remapped 200bhp), Alfa 147 GTA (3.6 295bhp), Alfa 159 (diesel remapped 245bhp 300ft.lbs @ 2500rpm)
Why isn't my daughter an Alfaholic? | |
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Posted: Sat May 04, 2013 1:21 am |
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Joined: May 01, 2013
Posts: 5
Trade Rating: 0
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Thanks so much!
What is the best way to check for air the cooling system and how to let the air out if any. That is one thing I have never tried... Will it be enough to run the engine with the cap of the coolant system?
Since the needle is "drifting" down to a low temperature (and up again as described) and not dropping like a falling stone, I don't expect a failing temperature sensor. If the signal was lost or bad I would expect the needle to jump fast from one point to another.
So my bet is still: a) air in the system or b) sticking thermostat.
Anybody has a describtion/picture/manual of how to get to the thermostat in a 1.4 HDi?
Thanks again
Best regards from Denmark
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Posted: Sat May 04, 2013 3:50 am |
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Joined: Aug 14, 2011
Posts: 61
Trade Rating: 0
Location: Finland
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The thermostat is between cylinder head and battery box. The way I did it, I first removed airbox and diesel filter, then all the hoses connected to the thermostat. Hardest part was to remove black bracket around the thermostat.
Now that I think about it, it will probably be easier just to remove the batterybox and see if that's enough.
The mechanical valve is inside the thermostat housing. Sensor is the green plug.
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Posted: Sat May 04, 2013 4:30 am |
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Joined: May 01, 2013
Posts: 5
Trade Rating: 0
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Thank you -that was really helpfull. Thanks
Hopefully I will be able to get this fixed.
Best regards -Denmark
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