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Discussion Starter #1
Good morning guys.

Yesterday i swapped over the thermostat for a new one. All pipes are in. Topped up water and anti-freeze. Once finished i left the car on idle and left the cap of for 15 minutes. Once put back together, The temp rises to 90 just fine, sometimes it goes past 90 until the fan kick in. But other times it might be at 90 and really really quickly jump down to 70 (in a matter of 2 seconds). It will then rise and do the same again.

Should it do this?
Can i just suspect air bubbles in the system?

So far i havent seen any leaks, every now and then i will take the cap off to release any pressure.

When changing the thermostat, i noticed their is a small notch on the black part of it. the new thermostat had this notch 90 degrees from the original ( pointed towards maf) I made sure that the jubilee clip was on really tight just incase of this small bit.
 

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air lock squeeze pipes to move it around system ...then go for a drive,let it cool ..then top up...and then keep an eye on level for next few days
 

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its normal for it to drop, as the thermo opens and lets in cool radiator water - when closed it heats and circulates coolant in the engine only... that's it job!

it doesn't do this when stuffed as the failure is half or permanently open... so the entire coolant volume slowly warms up uniformly...
 

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Discussion Starter #4
Squeezed some pipes for about 15 mins. Took it for a drive, it done it again when going to ninty it dropped to 70 with in 2 seconds. But after that it just stayed close to 90 for the rest of the drive. So happy now lol
 

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Nice site, although for the 156 1.8 alot of the work on your site is not needed. I have used the bleed screw and cant see any air entering the tank. As said it only drops to 70 when the car is first started and warmed to ninty the first time, after that it sits just below or just after 90
 

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i'm sure the temp guage sensor is mounted on the thermostat, so as someone stated earlier when it opens instant cool water flows over the sensor,
 

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A bleed screw eh?

Care to elaberate anyone? I know about leaving the cap off and letting the car bleed itself but a bleed screw is new to me....

I'm changing the Thermostat on my alfa soon so the more information the better
 

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Discussion Starter #10
i'm sure the temp guage sensor is mounted on the thermostat, so as someone stated earlier when it opens instant cool water flows over the sensor,
I understand that but.....

Does every single 156 have the same problem.

When starting the car in the morning and it has reached optimum temp, it jumps down to 70degrees then slowly creeps t 90 again.

If all alfa 156 do this then i have no problem, if not then their is still a problem to be fixed, weather it be bubbles in the system or a dodgy temp sender
 

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i'm sure this is normal. the alfa temp guage is a real time guage aswell so will fluctuate where as some other makes the sensors are not instant so temp averages out
 

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BUMPING this instead of creating ANOTHER thermostat thread.
Just changed mine:

1.old stat symptoms. constant kangarooing from 90 to 70, and when the car was moving it would also drop to 70.
poor mpg.

2.This Jan the needle barely moved. would climb only a few mm... so not even reach 70...
even worse mpg. running rich I assume.

3.Changed stat. needle kangaroos. but not affected by driving speed. It hits 90 quicker than before. drops to 70. climbs, drops etc. stabilises over time near 90.
Not yet checked MPG. too soon.
 
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you sure it's 70 it's dropping to?

In a 156 I find the gauge is not linear so you will find the line in between 50 and 90 is not actually 70 but 80. so if your temp is going between 90 and somewhere near 80 I would be less worried.

Some people say their gauge is rock solid at 90 but 156 gauges do not work like this and you will see them go up and down a bit as stat opens and closes. I think the cars with gauges solid at 90 have a less accurate gauge and would see similar to you if they looked at the ECU's temp.

Depends how quickly it drops if it goes from 90-70 like a switch it sounds like air in system. If it slowly starts to stabalise then move a little then over a few seconds drop to 70(or 80) then it sounds like stat opening.

Do you have good heat available in the cabin? Often airlocks stop the interior heating from working well.

John
 
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I love these thermostat threads...
We all automatically assume that replacing a thermostat will cure our coolant issues:lol:

personal experience has taught me that on alfa's especially, a thermostat will mask a lot of problems and only when we replace them it becomes more obvious...:rolleyes:

Radiator, radiator... Oh and check the radiator:rolleyes:
They don't last forever and don't be lazy:
Remove the bottom sump guard, get underneath with a torch and have a damn good look.... All radiators on alfa's look in pretty good nick when looking from above;)

Miraculously and assuming your water pump is ok, replacing both the radiator & thermostat at the same time is by far the best practice:thumbs::D
 

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BUMPING this instead of creating ANOTHER thermostat thread.
Just changed mine:

1.old stat symptoms. constant kangarooing from 90 to 70, and when the car was moving it would also drop to 70.
poor mpg.

2.This Jan the needle barely moved. would climb only a few mm... so not even reach 70...
even worse mpg. running rich I assume.

3.Changed stat. needle kangaroos. but not affected by driving speed. It hits 90 quicker than before. drops to 70. climbs, drops etc. stabilises over time near 90.
Not yet checked MPG. too soon.
what stat you put in ? you have an air lock in your system thus the constant swinging of your needle or new stat is faulty
 
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Not sure I agree on that one dave... Some peoples gauges do not move much but temp does.

My 155 V6 did it (even with good rad and new oem stat) my 156 1.8TS does it, My 20v Mjet does it, 155 TS's do it.

Due to where temp sensor is and alfa not having a buffered gauge you will see the temp on gauge and/or ecu moving as stat opens and closes.

Not quite as far down as the 80 line but the gauges do not sit dead at 90 all the time which is why I always think getting temps from ECU so you know what gauge is actually telling you is a good idea as all gauges seem to read just a little different some more sensitive than others.

Anyway seems he sorted it....
 

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Not sure I agree on that one dave... Some peoples gauges do not move much but temp does.

My 155 V6 did it (even with good rad and new oem stat) my 156 1.8TS does it, My 20v Mjet does it, 155 TS's do it.

Due to where temp sensor is and alfa not having a buffered gauge you will see the temp on gauge and/or ecu moving as stat opens and closes.

Not quite as far down as the 80 line but the gauges do not sit dead at 90 all the time which is why I always think getting temps from ECU so you know what gauge is actually telling you is a good idea as all gauges seem to read just a little diffrent.
john he describes system is breathing. his temp stabilises at 90c

ps on another note check valeo stats out for temp opening click on web catalogue top right:thumbs: Valeo Service UK and Eire (Unitedkingdom - EN) - Automotive Equipment - Automotive Industry Supplier - Automotive After Sales Service
 
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what i meant was when you put a new stat in and you aint used to alfas (not sure if he is or not) and the left mid line being 80ish and not 70 like you would assume the first stat opening can seem like air when you are not used to it. when my stats open the temp goes down quickly over a few seconds. Air in system i used to find made gauge jump from one to the other quicker than 2 seconds then jump back to 90 as water hit temp sensor again.

all depends how quickly the climb drop he is describing happens if it is up and down and up etc from one second to next then agree it's air. if it happens more slowly than that then maybe stat or he's not used to gauges in these cars....
 
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