Hi all.

2018 Mk8 1.1 85hp, 40K Km. I bought it used from a Ford dealer 3 years ago. I don't know much about car mechanics, so the fact that the coolant temperature rarely reached aprox 90°C wasn't too alarming to me. Weird, but not alarming.

I started reading here some people with the same exact issue, and how the coolant temperature reached 90°C quite fast after having the thermostat replaced.

The dealership said it's fine.

Heater works fine.

The hose from the thermostat to the radiator gets really hot way before the coolant temp reaches 92°C, the temperature at which the thermostat is supposed to open: https://navigates.gates.com/emea/p/thermostat--coolant/gates/th50292g1.html

I've extracted coolant temp (ECT, red), oil temp (EOT, orange), and speed data. Coolant rarely gets past 78°C, except at idle. At idle it can reach around 105°C, temperature at which the fan kicks in.

So, am I right? Is the dealership right? Is my engine going boom?

TIA. ✌️

Please guys, any help, insights about this would be really appreciated. 😣

The car is still under warranty, I'm really short on money, so before bitting the bullet and having the thermostat replaced by an independent tech, I'd like to know whether there's a more solid argument, some technical data, specs, I could use when going back to the dealership.

I think we all know what they're going to say about that live data I got using Forscan. 

So it runs fine, heater works fine and fuel economy is fine...  Can't see any cause for concern myself.  

If you can prove yours has a 92c stat then your data suggests it's not working perfectly.  However, in the UK stats are often 82c.  I don't have access to any Mk8 Fiesta parts catalogues to confirm.

7 minutes ago, TomsFocus said:

So it runs fine, heater works fine and fuel economy is fine...  Can't see any cause for concern myself.  

If you can prove yours has a 92c stat then your data suggests it's not working perfectly.  However, in the UK stats are often 82c.  I don't have access to any Mk8 Fiesta parts catalogues to confirm.

Hey, thank you very much for your answer. 

Well, thing is, without taking into account live data and all that stuff, the needle at the temp gauge rarely makes it to the middle, staying most of the time on the second line. 

That was the main concern for people at this thread for instance:

 

So, don't know what to do now. 

 

15 hours ago, TomsFocus said:

So it runs fine, heater works fine and fuel economy is fine...  Can't see any cause for concern myself.  

If you can prove yours has a 92c stat then your data suggests it's not working perfectly.  However, in the UK stats are often 82c.  I don't have access to any Mk8 Fiesta parts catalogues to confirm.

Hey.

Sorry for bothering you again, you've been to only person to take me seriously so far. 

I've been digging through the Ford ETIS and I've found this:

Thermostat starts opening at 92°C, completely open at 106°C. Should this be proof enough? 

Also, I've attached a PDF, the warming process goes through three phases, being the third the one at which the thermostat should open. If I've understand correctly, even with the thermostat open, part of the coolant from the block will flow directly to the heater,  bypassing the radiator. If you're so inclined to take a look at it, would this explain why even with a thermostat stuck open I'd still get hot hair from the heater?

I know I may sound desperate or something, but as I said before, I hardly know a thing about car mechanics, my financial situation right now isn't the best, and the car is still under warranty. That's why I need all the help I can get before going back to the dealership. Even if this seems to cause confusion to some users.

Thanks for your time, my apologies if I sound oh so dramatic.

 

Best regards, 

Luis.

 

 

 

Cooling operation.pdf

7 minutes ago, Kolmo74 said:

Hey.

Sorry for bothering you again, you've been to only person to take me seriously so far. 

I've been digging through the Ford ETIS and I've found this:

Thermostat starts opening at 92°C, completely open at 106°C. Should this be proof enough? 

Also, I've attached a PDF, the warming process goes through three phases, being the third the one at which the thermostat should open. If I've understand correctly, even with the thermostat open, part of the coolant from the block will flow directly to the heater,  bypassing the radiator. If you're so inclined to take a look at it, would this explain why even with a thermostat stuck open I'd still get hot hair from the heater?

I know I may sound desperate or something, but as I said before, I hardly know a thing about car mechanics, my financial situation right now isn't the best, and the car is still under warranty. That's why I need all the help I can get before going back to the dealership. Even if this seems to cause confusion to some users.

Thanks for your time, my apologies if I sound oh so dramatic.

That certainly does seem to confirm it as a 92c main 'stat on your car.  Whether the garage will accept that or not is a different matter though, it's them you have to persuade really, not us.

Heater hoses always do run straight from the block, there would be no point running them through the radiator.  Generally the overall temperature in the coolant is just too cold for acceptable cabin heat with a stuck 'stat.  This was shown in the other thread you linked where people were only getting 50-60c engine temp, which is what I'd expect with a stat that never closes.  That's not enough for a hot heater.  Yours sitting around 80c is a bit unusual, and unfortunately that may mean the garage won't accept your findings until the problem gets worse.

The 3 phase cooling cycle on this engine was very interesting.  Hadn't seen that info before. 

 

I had a stat stuck open. Symptoms identical to yours. Cabin heat was ok. Fuel consumption OK, but improved after I had the stat changed.

Needle never got to the middle of the gauge and as Tom kindly pointed out to me (and I've heard this elsewhere too) the gauge is calibrated to point at 90 deg over a wide range of temps so as not to worry drivers unnecessarily. So if your needle isn't getting anywhere near the middle the stat is truly faulty. Your graphs seem to confirm this - average around 73 deg??? That's significantly below an average of 90 or 92 (and did I see that if fully opens at 106 deg???)

Like you, I took mine to a garage who said "it's OK" - because they had run the car in their 20 deg workshop with no airflow through the rad - so of course it got up to a good temp (an indicated 90). I guess that's what your dealership did.

I believe your stat is stuck open. To persuade them I  I guess either

1. Persuade them that your Forscan data is reliable .

2. Ask them to do a similar diagnosis which they may want to charge for - if so, you 'll have to say "if your data confirms my data you will reimburse me for the diagnostic fee". 

3. If they say "they're all like that, sir" get them to take a drive in a similar model from their forecourt  - within 5 minutes the needle will sit in the middle of the gauge as it should, unlike yours.

Good luck.

 

My Engine is different to your one, but on mine the Coolant, Oil and Cylinder Head temperatures all rise in more or less the same linear fashion, within a few degrees of each other and max out roughly the same in the 90's under normal easy driving, a bit more than 100 when driven harder. 

47 minutes ago, alanfp said:

I had a stat stuck open. Symptoms identical to yours. Cabin heat was ok. Fuel consumption OK, but improved after I had the stat changed.

Needle never got to the middle of the gauge and as Tom kindly pointed out to me (and I've heard this elsewhere too) the gauge is calibrated to point at 90 deg over a wide range of temps so as not to worry drivers unnecessarily. So if your needle isn't getting anywhere near the middle the stat is truly faulty. Your graphs seem to confirm this - average around 73 deg??? That's significantly below an average of 90 or 92 (and did I see that if fully opens at 106 deg???)

Like you, I took mine to a garage who said "it's OK" - because they had run the car in their 20 deg workshop with no airflow through the rad - so of course it got up to a good temp (an indicated 90). I guess that's what your dealership did.

I believe your stat is stuck open. To persuade them I  I guess either

1. Persuade them that your Forscan data is reliable .

2. Ask them to do a similar diagnosis which they may want to charge for - if so, you 'll have to say "if your data confirms my data you will reimburse me for the diagnostic fee". 

3. If they say "they're all like that, sir" get them to take a drive in a similar model from their forecourt  - within 5 minutes the needle will sit in the middle of the gauge as it should, unlike yours.

Good luck.

 

 

21 minutes ago, Tizer said:

My Engine is different to your one, but on mine the Coolant, Oil and Cylinder Head temperatures all rise in more or less the same linear fashion, within a few degrees of each other and max out roughly the same in the 90's under normal easy driving, a bit more than 100 when driven harder. 

Thank you guys.

What infuriates me the most is shortly after the covid confinement ended here (Spain), just 3 months after I bought the car, I told the salesman about the car not reaching the middle of the gauge, and he was like "eh, don't worry, that's all electronically controlled". Since I have a technical background I was happy with that answer.

Since then, "weird" brake pedal behavior, dirty/soiled head gasket...nah, it's all fine, they're all like that. And I paid (happily) an extra just because that particular car was under their "Ford Selection" program and came with the Ford Protect extended warranty... 😣

 

Thanks again for your time guys, I'll keep you updated about how I fare against a giant corporation...😅

 

Best regards,

Luis.

8 hours ago, alanfp said:

I had a stat stuck open. Symptoms identical to yours. Cabin heat was ok. Fuel consumption OK, but improved after I had the stat changed.

Needle never got to the middle of the gauge and as Tom kindly pointed out to me (and I've heard this elsewhere too) the gauge is calibrated to point at 90 deg over a wide range of temps so as not to worry drivers unnecessarily. So if your needle isn't getting anywhere near the middle the stat is truly faulty. Your graphs seem to confirm this - average around 73 deg??? That's significantly below an average of 90 or 92 (and did I see that if fully opens at 106 deg???)

Like you, I took mine to a garage who said "it's OK" - because they had run the car in their 20 deg workshop with no airflow through the rad - so of course it got up to a good temp (an indicated 90). I guess that's what your dealership did.

I believe your stat is stuck open. To persuade them I  I guess either

1. Persuade them that your Forscan data is reliable .

2. Ask them to do a similar diagnosis which they may want to charge for - if so, you 'll have to say "if your data confirms my data you will reimburse me for the diagnostic fee". 

3. If they say "they're all like that, sir" get them to take a drive in a similar model from their forecourt  - within 5 minutes the needle will sit in the middle of the gauge as it should, unlike yours.

Good luck.

 

Hey.

Sorry, I forgot to ask. How did you get it replaced? Was your car under warranty still?

On 11/14/2023 at 11:48 AM, Kolmo74 said:

I don't know much about car mechanics

Maybe so, but from reading your posts describing your analysis and diagnosis I bet you've got what it takes to fix it yourself (by replacing the thermostat) as it is only a few bolts and shifting hoses out of the way. You may find that's an easier path to take than convincing the dealer that the current situation isn't within spec which, to be fair, isn't so explicitly defined - sure we know the functional parameters for the stats but I bet the user manuals for the car likely say something along the lines 'everything is fine as long as it is not in the red'.

1 hour ago, MJNewton said:

Maybe so, but from reading your posts describing your analysis and diagnosis I bet you've got what it takes to fix it yourself (by replacing the thermostat) as it is only a few bolts and shifting hoses out of the way. You may find that's an easier path to take than convincing the dealer that the current situation isn't within spec which, to be fair, isn't so explicitly defined - sure we know the functional parameters for the stats but I bet the user manuals for the car likely say something along the lines 'everything is fine as long as it is not in the red'.

You're clearly overestimating my abilities. 😅

I live at an apartment,  so I don't have a shop where to work or anything, and here in Spain you can't do repairs in public areas if they involve fluids.

Regarding the working temperature, all the manual says is it's fine as long as the needle is in the middle section. Thing is the temp gauge has 4 sections, so which one is the one in the middle? More than likely it's as you say, as long as it's not in either the blue or red areas, it's fine.

Worst case scenario, I'll have the stat replaced at an independent tech.

Thanks for your time. 

Best regards, 

Luis. 

1 minute ago, Kolmo74 said:

You're clearly overestimating my abilities. 😅

I live at an apartment,  so I don't have a shop where to work or anything, and here in Spain you can't do repairs in public areas if they involve fluids.

Oh wow, never knew that! To be honest I do sometimes wonder what ends up going down our drains when people work on their cars in the road/drive.

Quote

Worst case scenario, I'll have the stat replaced at an independent tech.

Yeah might be worth it if DIY isn't an option (and the garage don't roll over). Consistently running below target temperature will impact efficiency somewhat. By how much I don't know but it'll certainly be non-zero.

2 hours ago, Kolmo74 said:

How did you get it replaced? Was your car under warranty still?

No, my car was 7 years old when it failed. I paid an independent agarage to supply and fit the part.

I've finally had the time to do some tests after having the stat replaced under warranty, although I could already see the temp gauge basically glued to the middle the whole time, aaaaaand...

Bam! coolant temp (red line)  fluctuating around 90°C the whole time! 😁🥳

 

Thank y'all for your help,

Cheers! ✌️

Exactly as my post above, the Cylinder Head temperature would have been just as the other two if you had monitored it, perhaps just a few degrees above the others while warming up. 

34 minutes ago, Tizer said:

Exactly as my post above, the Cylinder Head temperature would have been just as the other two if you had monitored it, perhaps just a few degrees above the others while warming up. 

Is there an actual, physical temp sensor for the cylinder head? AFAIK the oil temperature is just an inferred value, since there is not an oil temp sensor, is this correct? I'll add the cylinder head temp for my next tests.

Thanks! ✌️

46 minutes ago, Kolmo74 said:

Is there an actual, physical temp sensor for the cylinder head? AFAIK the oil temperature is just an inferred value, since there is not an oil temp sensor, is this correct? I'll add the cylinder head temp for my next tests.

Thanks! ✌️

I know there is a Cylinder Head temperature sensor on my Engine but not sure about your Engine. I would be surprised if there was not one. 

I think that the Oil Temperature Sensor will be incorporated into the Variable Control System rather than a separate sensor but I'm not certain about that. Remember that in your first screenshot the Oil Temperature was as expected for an Engine with a defective Cooling System Thermostat. If it was an implied value based on the Coolant then I would have expected it to be nearly the same as the low Coolant Temperature.