I know this has been discussed before but I cannot find definitive answers; should the temperature gauge on a 150hp multijet reach the middle and stay there?

Mine works like this: when I start the car and the engine warms up, the needle goes right up to the middle; after sitting there for a few minutes, if it's not too warm outside, it drops back down one notch and stays there - if the engine load is greater it goes back up to the middle. I always thought that the thermostat opens as soon as it hits operating temperature and therefore the needle drops. But I've read a few comments on this forum that the needle should ALWAYS stays upright once it warms up.
The needle doesn't ever drop under this position, even if it's really cold outside and I drive under 2krpm. Shouldn't the needle drop further if I had a faulty thermostat?

All i can say is mine when reached 1/2 way stays there , even in winter and just coasting no boost etc i dont see it move off 1/2 way.
Sounds a bit like thermostat sticking open a bit?

Thank you!

I guess I'll have to replace mine.

Im hoping mine lasts till i can get a cambelt waterpump and coolant change probably do thermostat at same time anyway.

Does a lot of coolant leak when you remove the thermostat? And do you have to bleed the system after you add the coolant back?
I've just changed the coolant a few months ago so I'm really not in the mood to do it all over again

I found my 1.2 spat about half a cup of coolant when I took off the thermostat housing. I had a pan ready to catch it.... make sure you do too, that stuff is nasty to Cats.

Changing the thermostat is a piece of cake to do, not hard at all.

Best not to wait too long in replacing it, if you know its stuck wide open it might be "ok". But if the stat is still moving there is equally every chance it will stick closed..... causing unimaginable nightmares to your engine if it cooks!

Thank you!

It won't overheat, I'm always watching the temperature gauge obsessively. The only reason I didn't already change it is because I've found some more posts on alfaforums where people changed their thermostats and water temperature stayed the same, ie fluctuating.

For time being I'll keep watching the temperature gauge and if it drops any further at any point I'll go ahead and change it.

Edit: I've been reading some more and I guess it's really faulty. Now I need to find a good replacement.

Looks like its all built into a complete housing
I know you said youve been on alfaforum but
http://www.alfaowner.com/Forum/engi...ow-to-change-a-thermostat-on-a-twinspark.html
This looks pretty similar to mine from memory not sure about space im sure ecu are in way on ours and egr cooler maybe.
Anyway looks like this is it
http://www.shop4parts.co.uk/?name=s...ermostats_&_Flanges&cat=Thermostats_&_Flanges
Also here
http://www.eurocarparts.com/mobile/...56c83053085162e535161ff3c6581297170e3d&000325
£90 for thermostat and a gasket also
Looks like operating temp for stat is opening at 88c
I had a quick look on bay of e and found some between £60-100
At that price you gotta ask how bothered are you its running a bit cool.
Post back anyway especially if you buy cheaper than above.

I've actually ordered this one (Behr Thermot-Tronik TI 146 88 Thermostat, coolant: Amazon.co.uk: Car & Motorbike) which is 52pounds delivered (to Slovenia, probably cheaper in the UK) but the Amazon rep I spoke with isn't sure if it will be back in stock. At this price I think it's worth a try, since it's made by Behr which is supposed to be good stuff

I've found Opel thermostats for around 30pounds (or Vauxhall for UK forum members ) for the 1.9CDTI engine which is veeeery similar, but some hose attachments are at a different angle and I'm not willing to risk it, since I'm ordering from outside my country. But on the other hand, some folks on the alfaforums posted that it fits, so who knows.

If I get an email from Amazon that they've restocked the thermostats I'll post here, might be a great price for anyone who needs a thermostat.

And another quick question - what is your preferred method of bleeding the cooling system? Do you run the car hot with the expansion tank cap off or do you bleed it on the all 3 bleeding screws?

Exacly like mine (1.6). I changed the thermostat and it cured it. Every downhill, the temp would fall.

https://www.fiatforum.com/stilo-gui...oolant-heater-install-gearbox-oil-top-up.html

Not for the 150 engine, but a method of bragging of my excellent guide.

fruchty said:

And another quick question - what is your preferred method of bleeding the cooling system? Do you run the car hot with the expansion tank cap off or do you bleed it on the all 3 bleeding screws?

Click to expand...

You can run it with the cap off (will not get the greatest of pressure) and watch coolant flow when the thermostat opens. Turn on A/C full chill (not heat, as it will prevent coolant from getting hot), high beam, heated seats etc. to load the engine max at idle, or it will take ages to reach operating temp when cold outside.

Morty Mort said:

Exacly like mine (1.6). I changed the thermostat and it cured it. Every downhill, the temp would fall.

https://www.fiatforum.com/stilo-gui...oolant-heater-install-gearbox-oil-top-up.html

Not for the 150 engine, but a method of bragging of my excellent guide.

Click to expand...

All this time I thought "harmful for cats" was an inside joke, but now I finally understand

Thanks for the link!

The plot thickens...I guess

Today I coasted up to a petrol station and I waited a few minutes, standing still... Driving up was a very easy drive, I probably didn't go over 2krpm for a few kilometers. Anyway, the temp gauge was like this:


And then the fan came on! While the gauge was like this, the fan turned on and I wasn't running AC.
Does this change anything? It looks suspicious to me...

Fact is even if the gauge is reading low( if you suspect gauge showing low as fan kikked in below 90c) the gauge still settles on a higher position and then drops still suspect thermostat.
To be 100% sure you need a diagnostic lead and free or paid for software to read real engine temp as the ecu sees it.
The other thing from alfaforum is a lot of cars running at 90 but showing 70 on gauges.
With software and a lead you can log temps and check temps etc.
On multiscan theres even a gauge check that will put your gauges to full, 1/2 , etc( on paid version , not sure about free version)
I think the ecu gets its temps from the green probe in the thermostat housing, try cleaning plug and connectors on sensor and lead.
Also i think ecu tells either fan speed 1 or 2 from coolant temp unless theres another sensor or switch near radiator?

I was fiddling with something else today and I just briefly checked the engine temparature in multiecuscan; it was 91,x and the gauge was fully upright.
I'll check it again when the gauge drops and report

I checked the temperature yesterday again after a long drive, as the gauge was positioned like on that picture I posted - it was 71,8-72,6°C.

But the fan came on nonetheless... Which is weird?

OK guys so now once and for all - if your temperature gauge doesn't stay up, something isn't working properly.

I changed my thermostat today, after much swearing. and now the needle always stays fully upright.

Good , hopefully last a good few years now.
Keep this thread alive in a month or so if your mpg has increased much.
Its going to go down due to weather getting colder anyway.

You think running on 70degrees made a difference in mpg? I'll be checking it out, I'm really curious if that's the case.

Anyway, some users on alfaforums reported that thermostats last only for about 50kkm...