Technical Thermostat change, what coolant?

[Kieranscottroberts5]

Hello guys,

Fiat Panda 1.1 2010

I was driving on the motorway today and noticed the temperature gauge wasn’t sitting at the halfway mark. It gets to temperature whilst doing short trips however. The EML came up and the temperature gauge dropped to 0. I had the code P0115 engine coolant temperature sensor 1 circuit. I deleted the code and restarted the engine. The temperature gauge then worked and my code reader read the coolant temperature at 60/65 degrees and rising. This is awfully low for a 1 hour motorway drive I thought. The heater blowers were warm but not toasty.

So it screams thermostat. I’ve just ordered a new one. However I can’t really tell what colour the coolant it is, to be fair it’s defiantly more red than violet/pink. (Cambelt and waterpump had been changed 20,000 miles ago during previous ownership).

The question is, what coolant should I use that I can grab off the shelf or from Amazon (prime delivery!) I know about OAT etc just worried about potentially mixing?!

To be honest I’m going to change the cambelt and waterpump in the next few weeks so it will have a full flush then too.

Thank You

 

[koalar]

Always best to drop the coolant and refresh

The rubber from the thermostat will have deteriorated, most likely due to the coolant going acidic

Oat is correct

It's easier to syphone the old coolant than remove the bottom hose

You can never get it all out anyhow

Even if you remove the bottom hose about a litre stays in the water jackets

 

[ultrasonic]

U can also syphon what coolant you can, and then fill multiple times with DI water, syphoning each time, until the water is clear (within the course of like a week) Best done during summertime. Then remove HALF of the coolant and add same volume of concentrate (instead of ready to use). That way you will make the required dilution "in-situ".

If you are changing the thermostat, you can use a tube to remove the remaining coolant from the bottom of the block.

Regarding coolant type, IF you removed all the old coolant, most modern coolants are backwards compatible... In any case, Fiat says paraflu-up.

 

[Greasytrucker]

If you’ve got a Euro car parts local to you they always have it in the reception area where you pay/pick orders up, there’s is a proper pink colour so you can’t miss it. Good price from there as well, just make sure you pick up the concentrated as apposed to ready to use

 

[Pugglt Auld Jock]

My nearest local Factor is now part of the global Napa brand and always have the 3 most common types on shelf. Most vehicles these days will use OAT technology G12 which is red in colour. I've been putting this in Fiats for years now. Before that it was a silicate based fluid which is usually blue and they keep that too. (some silicate "brews" were green though so don't necessarily go by the colour). Then you've got the very latest Violet/Purple coloured G13. the only car in the family fleet which uses this is my Scala. The OAT based fluids are good for at least 5 years whereas the older silicate stuff was best changed every year or so. This is not so much because the antifreeze component degrades but rather that the additive package which slows/prevents corrosion and electrolytic leaching between dissimilar metals degrades in use.
Here is the Napa site which describes their whole range, Hope it's helpful. Other brands produce similar products: https://napaautoparts.eu/en/products/antifreeze-2/

 

[Mike1alike]

Here is a little bit to read about coolants.

https://www.fcpeuro.com/blog/how-to-pick-the-right-coolant-for-your-car

Although... that may look like one of those things, the more you read, the more confused you get about which one to pick.

Short answer for your question @Kieranscottroberts5 I think is red/pink color and one of G12/G12+/G12++ type suits your engine.

 

[Kieranscottroberts5]

Thanks for your replies guys, this just arrived in the post along with the thermostat. Gotta love Amazon prime!

 

[Pugglt Auld Jock]

Thanks for your replies guys, this just arrived in the post along with the thermostat. Gotta love Amazon prime!

View attachment 483775

That'll do nicely I'm sure.

 

[Kieranscottroberts5]

I’m still waiting on a big order from AutoDoc, so when It arrives, I’m going to do the Cambelt and waterpump and lots more. I’ve got 5 litres along with that order of -37 degrees G12 so the whole cooling system will have a proper flush then! This should get back on the road until I do that work in a few weeks!

Thanks for your help everyone!

 

[Mike1alike]

so the whole cooling system will have a proper flush then!

There are products for flushing the cooling system. The most efficient substance for that though is the citric acid. Mix 50 g citric acid to 1 L distilled water and run the engine ~15 mins with that instead of coolant. Then flush that out and rinse the system with distilled water 2-3 times.
Reverse flush is very useful, done to radiator and heater matrix. No pressure needed, just filling with water (overfill) and let the water go out to the normal use "In" pipe. Your radiator has now in it the ruber debris from damaged thermostat internal gasket, reverse flushing it gets those out quickly.
If you do that you'll have a clean cooling system and that is extremely useful to have on the car. Keeps perfect engine temperature and gives heat inside the czbin when you need it.

 

[koalar]

How to over complicate a simple problem, Not getting up to temperature,.change the thermostat and coolant, done

Flushing with an acid without an inhibitor is in my opinion a stupid idea and a pointless risk

Loosened debris can move in to narrow passages

It will weaken gaskets.and.seals

You can't flush it totally out and should be properly neutralise

It removes some metal, scale and rust might be holding the cooling system together

In hard water areas it will cause crystals to form, you don't know what's already in the engine

It doesn't remove sludge, oil

50g citric acid to 1L is far too strong

Aluminium form a protective oxide layer which prevents further corrosion removing it leads to further pitting

And so on

Yes it's been done, both successfully but also with negative consciousness

Out board engines for example have fresh water constantly flushing it out

Following YouTubers and Google AI is all well and good, until isn't

 

[Pugglt Auld Jock]

How to over complicate a simple problem, Not getting up to temperature,.change the thermostat and coolant, done

Flushing with an acid without an inhibitor is in my opinion a stupid idea and a pointless risk

Loosened debris can move in to narrow passages

It will weaken gaskets.and.seals

You can't flush it totally out and should be properly neutralise

It removes some metal, scale and rust might be holding the cooling system together

In hard water areas it will cause crystals to form, you don't know what's already in the engine

It doesn't remove sludge, oil

50g citric acid to 1L is far too strong

Aluminium form a protective oxide layer which prevents further corrosion removing it leads to further pitting

And so on

Yes it's been done, both successfully but also with negative consciousness

Out board engines for example have fresh water constantly flushing it out

Following YouTubers and Google AI is all well and good, until isn't

I found this interesting. I'm quite a fan of back flushing and have done it many times with varying success including promoting leaks where there were none before! Never heard of using any sort of acid flush though.

Personally I wouldn't be doing that for the reasons put forward by koalar above.

 

[koalar]

I found this interesting. I'm quite a fan of back flushing and have done it many times with varying success including promoting leaks where there were none before! Never heard of using any sort of acid flush though.

Personally I wouldn't be doing that for the reasons put forward by koalar above.

Used to be used quite a lot on old classic cars

Big iron blocks and heads with copper or brass core radiators

But things move on, unfortunately once on the internet it just get copied by other

Same with spark plug colours, a carb engine on leaded fuel, is not the same same as a euro 5 or 6 on modern pump, so most of the guides are just plain wrong

I have used dishwasher tablets after a head gasket oil and water mix

But I understand the risks.and would recommend others to follow without at least knowing the risks first

 

[Mike1alike]

I found this interesting. I'm quite a fan of back flushing and have done it many times with varying success including promoting leaks where there were none before! Never heard of using any sort of acid flush though.

Personally I wouldn't be doing that for the reasons put forward by koalar above.

If you see what comes out after you do it, you'd probably change your mind.
First time I did it, about 5 years ago, was because of clogged heater matrix. First I used dedicated flush product, that did absolutely nothing and then a mechanic who presented himself "a specialist in cooling systems" told me the only fix would be a new heater matrix. That means dashboard down, of course and I wanted something simpler.
I found out about the citric acid method and I did it. Heater matrix still works today and gives very much heat.
Citric acid is a very good cleaner and it's safe to all components of the cooling system.
The dirt that came out was very intense and also had a strong stench, sewage stench. And I'm not the only one who cleaned it like this, I'm not the one who invented it and I told people about it too, I even wrote a thread topic on this forum about it. People who did it after I told them reported they were impressed with the amount of dirt coming out and the stench too.
Yes, much dirt must have come out of the heater matrix, it being clogged and the reason I did the cleaning to begin with. But my assessment about it is much part of that came from the engine channels. I've seen people wondering why their coolant goes rusty coloured soon as they put it in. They couldn't see where the rust was coming from. Iron cast engine blocks' cooling channels do rust on the inside, no matter what the coolant people brag about their products and additives in it.
This winter, December 2025 I did another citric acid flush. Dirt still came out, not the stench this time. I did it because of heater matrix not working again but it turned out it was clogged, but not as the first time. This time was pieces of paint blocking it, they came from inside of the metal pipe on the system. That came out on reverse flushing. So I could have done just water flush this time. Very idiotic idea to paint that pipe inside, I put new pipe a while ago and paint just peeled off.
And here are some pictures showing what I'm talking about.

 

[koalar]

Loosened debris can move in to narrow passages

It removes some metal, scale and rust might be holding the cooling system together

The above post just proves what I said

And unnecessary complicated a half hour job

Out of the billion and a half cars on the road there must be tens of thousands of cars a day that just have the coolant changed at a dealership, without issue

It's an unnecessary risk

Beware of the citric acid flush - you've been warned - PeachParts Mercedes-Benz Forum

I went to do a citric acid flush today on the 85. Car is newish to me and it was time to get rid of the green coolant. Did the flush by the book and

www.peachparts.com

 

[Greasytrucker]

First time I did it, about 5 years ago, was because of clogged heater matrix.

Makes sense if you’re doing it to try and solve a problem, but completely unnecessary for a routine coolant change

 

[Mike1alike]

Makes sense if you’re doing it to try and solve a problem, but completely unnecessary for a routine coolant change

Yes, but once in an engine lifetime, I totally recommend it!
To clean the engine block's channels.
And people are trying to keep it in shape, they do buy flush products. They just don't work. What I tried there before citric acid was Liqui Moly I think. Heater matrix didn't unclog with it not even a bit and all that dirt came out after doing it with citric acid.