Hello,

I have had my 2017 Ford Focus Sport for a few months now, haven't had a single issue so far and had it serviced twice, no issues either time. I went to check my oil this afternoon after work and noticed my coolant reservoir was basically 100% empty. The car drives fine, there's no overheating warnings or anything like that and upon looking through the engine bay I couldn't see any obvious signs of leakage. Just wondering if anyone has any simple ideas before I go to the mechanic on Monday and fork out some money. 

Also is it normal for the engine to not have overheated or given me any warning indicators/signs? 

Cheers

Hi,

We haven't had a Sport trim in the UK since 2007.  If this is a 2017 then I assume it's a Mk3 facelift?  Is it a diesel?  I would have expected a 1.0 EcoBoost to blow up by now if there really wasn't any coolant in it.  Ford saved money by not fitting level sensors to the coolant reservoir so it's not unusual not to get a warning for low coolant until the engine gets too hot.

11 minutes ago, TomsFocus said:

Hi,

We haven't had a Sport trim in the UK since 2007.  If this is a 2017 then I assume it's a Mk3 facelift?  Is it a diesel?  I would have expected a 1.0 EcoBoost to blow up by now if there really wasn't any coolant in it.  Ford saved money by not fitting level sensors to the coolant reservoir so it's not unusual not to get a warning for low coolant until the engine gets too hot.

 

Hi mate,

Not a diesel no and I am in Australia. It is a '2017 Ford Focus LZ Sport, 1.5L Petrol 6 speed auto'.

3 minutes ago, niafrok said:

 

Hi mate,

Not a diesel no and I am in Australia. It is a '2017 Ford Focus LZ Sport, 1.5L Petrol 6 speed auto'.

Thanks for confirming.  I take it that's a 1.5 EcoBoost (turbo) which is a stronger engine than the 1.0 EcoBoost, but they still suffer with cooling issues.

This loss of coolant could be caused by internal engine damage on this engine.

It could also be caused by something simple like a faulty cap or a crack in the reservoir.  Best option is to fill it up again, run it until it gets hot and keep checking for any visible leaks.

17 hours ago, TomsFocus said:

Thanks for confirming.  I take it that's a 1.5 EcoBoost (turbo) which is a stronger engine than the 1.0 EcoBoost, but they still suffer with cooling issues.

This loss of coolant could be caused by internal engine damage on this engine.

It could also be caused by something simple like a faulty cap or a crack in the reservoir.  Best option is to fill it up again, run it until it gets hot and keep checking for any visible leaks.

 

Appreciate the response, will try this tomorrow. Really hope nothing major is wrong as the warranty has just expired as well. 

The older 4-cylinder 1.5 EcoBoost belongs to the Sigma engine family and is basically a redesign of the 1.6 EcoBoost. The displacement decreased to 1.5 Liter due to tax reasons for mainly the Chinese market. The 1.5 and 1.6 EcoBoost engines have the exact same bore but the 1.5 EcoBoost has a shorter stroke due to a different crankshaft. 

Like the 1.6 EcoBoost the 1.5 ECOboost Sigma engine has an open deck engine design with cooling slots between the cylinders. The cast iron liners are casted into the aluminium engine block and do not reach all the way to the top. In other words, the head gasket does not seal directly onto the liners but on the aluminium of the engine block that the liners are casted into. 

In my opinion this design is extremely sensitive to temperature differences inside the engine block. It is very important that the engine reaches its operating temperature before demanding any serious power.

Failing this will result in uneven expansion of the different engine components (most important the open deck cylinders and the cylinder head) which will eventually cause head gasket failure and coolant to leak in the cylinder. On this engine it is usually cylinder 2 or 3 that fails. This can be explained by the fact that the exhaust manifold is fully integrated into the cylinder head and is very close to cylinder 2 and 3. In my opinion these cylinders suffer the most from temperature differences. Especially during warming up when the water pump is not engaged (the water pump on this engine has a clutch that is controlled by the PCM to warm up faster). 

When coolant loss is detected in time the problem can usually be solved by just replacing the head gasket. However, when the coolant loss is not detected in time it usually results in severe damage of the aluminium engine block or even piston failure. In many cases the aluminium material on top of the liners where the head gasket seals onto is simply burned away by a combination of escaping combustion gases and coolant.

In 2019 Ford redesigned the engine block of the 4-cylinder 1.5 ECOboost. The open deck engine design remained but the cooling slots between the cylinders were replaced by angular drilled holes. This revised engine was never used on the Focus MK3.5 because the MK3.5 was already out of production at the time that the revised engine was released. The revised engine was used on other Ford models like the Kuga MK2.5.

Considering the fact that the redesigned version was only used in production for quite a short period it is impossible to tell whether the redesign actually solved the problem or not.


Considering that lots of these engines were sold the failure rate is actually still quite low. However, it is still a well known and widespread problem. As a result of this, used engines are extremely hard to find (demand is much larger than supply). Due to the fact that a brand-new service engine from Ford is currently listed for over 10,000 GBP a low mileage, good condition used engine is also worth quite a lot of money.


In this case I recommend to start with a pressure/vacuum test of the cooling and a compression test. If any of these test indicate an internal leak the cylinder head should be removed for further diagnosis.

 

 

23 hours ago, JW1982 said:

The older 4-cylinder 1.5 EcoBoost belongs to the Sigma engine family and is basically a redesign of the 1.6 EcoBoost. The displacement decreased to 1.5 Liter due to tax reasons for mainly the Chinese market. The 1.5 and 1.6 EcoBoost engines have the exact same bore but the 1.5 EcoBoost has a shorter stroke due to a different crankshaft. 

Like the 1.6 EcoBoost the 1.5 ECOboost Sigma engine has an open deck engine design with cooling slots between the cylinders. The cast iron liners are casted into the aluminium engine block and do not reach all the way to the top. In other words, the head gasket does not seal directly onto the liners but on the aluminium of the engine block that the liners are casted into. 

In my opinion this design is extremely sensitive to temperature differences inside the engine block. It is very important that the engine reaches its operating temperature before demanding any serious power.

Failing this will result in uneven expansion of the different engine components (most important the open deck cylinders and the cylinder head) which will eventually cause head gasket failure and coolant to leak in the cylinder. On this engine it is usually cylinder 2 or 3 that fails. This can be explained by the fact that the exhaust manifold is fully integrated into the cylinder head and is very close to cylinder 2 and 3. In my opinion these cylinders suffer the most from temperature differences. Especially during warming up when the water pump is not engaged (the water pump on this engine has a clutch that is controlled by the PCM to warm up faster). 

When coolant loss is detected in time the problem can usually be solved by just replacing the head gasket. However, when the coolant loss is not detected in time it usually results in severe damage of the aluminium engine block or even piston failure. In many cases the aluminium material on top of the liners where the head gasket seals onto is simply burned away by a combination of escaping combustion gases and coolant.

In 2019 Ford redesigned the engine block of the 4-cylinder 1.5 ECOboost. The open deck engine design remained but the cooling slots between the cylinders were replaced by angular drilled holes. This revised engine was never used on the Focus MK3.5 because the MK3.5 was already out of production at the time that the revised engine was released. The revised engine was used on other Ford models like the Kuga MK2.5.

Considering the fact that the redesigned version was only used in production for quite a short period it is impossible to tell whether the redesign actually solved the problem or not.


Considering that lots of these engines were sold the failure rate is actually still quite low. However, it is still a well known and widespread problem. As a result of this, used engines are extremely hard to find (demand is much larger than supply). Due to the fact that a brand-new service engine from Ford is currently listed for over 10,000 GBP a low mileage, good condition used engine is also worth quite a lot of money.


In this case I recommend to start with a pressure/vacuum test of the cooling and a compression test. If any of these test indicate an internal leak the cylinder head should be removed for further diagnosis.

 

 

 

Appreciate the lengthy writeup, such great detail and information. I am going to just take the car to the mechanic on Monday, safest bet.

On 9/5/2025 at 5:31 PM, TomsFocus said:

Thanks for confirming.  I take it that's a 1.5 EcoBoost (turbo) which is a stronger engine than the 1.0 EcoBoost, but they still suffer with cooling issues.

This loss of coolant could be caused by internal engine damage on this engine.

It could also be caused by something simple like a faulty cap or a crack in the reservoir.  Best option is to fill it up again, run it until it gets hot and keep checking for any visible leaks.

Hey mate,

Went to fill up the coolant today and test for leaks, however noticed there is a lot more in the reservoir compared to Friday - see pic below in comparison. Assuming there was actually nothing wrong and I am quite silly? Either way, I topped it up a little bit and will monitor what happens.

1 hour ago, niafrok said:

Hey mate,

Went to fill up the coolant today and test for leaks, however noticed there is a lot more in the reservoir compared to Friday - see pic below in comparison. Assuming there was actually nothing wrong and I am quite silly? Either way, I topped it up a little bit and will monitor what happens.

There is something wrong.  There is an airlock in the system now.  Air is likely getting in through a leak where coolant is getting out.

3 hours ago, TomsFocus said:

There is something wrong.  There is an airlock in the system now.  Air is likely getting in through a leak where coolant is getting out.

Is there something I can do myself to test/fix this or is it more of a mechanics job? 

1 minute ago, niafrok said:

Is there something I can do myself to test/fix this or is it more of a mechanics job? 

Still the same as before, run it until it gets hot and then look around all of the pipework for leaks.  Depending on which part is damaged, it may be a garage job or may be something you could change yourself.

If you can't see any external leaks then have a garage do a CO2 sniff test.  This should be free if you're likely to use their repair services, although you can buy a test kit yourself for around £10.  (Can't imagine that would be much different over there).  

If the sniff test fails then that shows exhaust gasses in the coolant which means major engine repair.  If the sniff test passes then you can have a pressure test done as Wilco suggests, which will literally force the coolant out of any gaps where it might not be easily visible under normal conditions.

On 9/9/2025 at 10:31 PM, TomsFocus said:

Still the same as before, run it until it gets hot and then look around all of the pipework for leaks.  Depending on which part is damaged, it may be a garage job or may be something you could change yourself.

If you can't see any external leaks then have a garage do a CO2 sniff test.  This should be free if you're likely to use their repair services, although you can buy a test kit yourself for around £10.  (Can't imagine that would be much different over there).  

If the sniff test fails then that shows exhaust gasses in the coolant which means major engine repair.  If the sniff test passes then you can have a pressure test done as Wilco suggests, which will literally force the coolant out of any gaps where it might not be easily visible under normal conditions.

 

Hey mate,

No coolant in the reservoir again today. Had a bloke at work who is knowledgeable with cars have a look and check a few little things. He couldn't find any coolant in the oil, no leaks in the engine bay and no white smoke or water in the exhaust. He suggested maybe the water pump but doesn't know. Been doing some research and seems as though the 1.5L Ecoboost from around 2017 is an absolute nightmare, commonly having the leaking coolant issue around 100,000KM's, which is what I have just surpassed.

Biting the bullet and going to the mechanics tomorrow morning, absolutely fearing the worst. Will update. 

On 9/9/2025 at 10:31 PM, TomsFocus said:

Still the same as before, run it until it gets hot and then look around all of the pipework for leaks.  Depending on which part is damaged, it may be a garage job or may be something you could change yourself.

If you can't see any external leaks then have a garage do a CO2 sniff test.  This should be free if you're likely to use their repair services, although you can buy a test kit yourself for around £10.  (Can't imagine that would be much different over there).  

If the sniff test fails then that shows exhaust gasses in the coolant which means major engine repair.  If the sniff test passes then you can have a pressure test done as Wilco suggests, which will literally force the coolant out of any gaps where it might not be easily visible under normal conditions.

Just picked up the car from the mechanic, he said he honestly couldn’t find anything wrong. Kept the pressure test on for nearly an hour and the needle didn’t drop whatsoever, checked every hose and found no leaks anywhere. Told me to top it up a little more and keep an eye on it and to come back if it loses more. 
 

Thoughts? 

4 hours ago, niafrok said:

Thoughts? 

An hour isn't nearly long enough for a pressure test.  Needs to be overnight for a minor leak really.

Was a sniff test done to rule out any exhaust getting into the coolant?

As Tom already mentioned performing a pressure test for just an Hour is way too short in case of a supected small internal leak.


The static pressure test should be performed for at least 12 Hours at a pressure of 25 psi (1.72 bar).

If no pressure loss is detected the dynamic pressure test should be performed. To do this you start the engine (with the pressure gauge still connected) and let the engine run at 2000 RPM until normal operating temperature is reached. With the engine running at normal operating temperature the system should keep pressure for a minimum of 5 Hours.

After 12 Hours (static pressure test) or 5 Hours (dynamic pressure test) a pressure drop of 4 psi (0.28 bar) is considered to be acceptable.

If both the static and dynamic pressure tests do not indicate a leak a vacuum test should be considered. Drain the coolant (drain valve at the bottom of the radiator) and after the system is drained apply a vacuum of 12.3 - 13.8 psi (0.85 - 0.95 bar). The system should hold vacuum for at least 1 Hour.

Once the vacuum test is completed the remaining vacuum inside the system is used to draw in fresh coolant into the system (vacuum filling). This is the only (and prescribed) way to fill the system without introducing air into the system.


If both the pressure and vacuum tests do not indicate a leak, it is likely that the problem is caused by the coolant reservoir cap. This is the only part of the cooling system that is not tested during the pressure and vacuum tests.

The EcoBoost engines are known to run considerably hotter than a conventional naturally aspirated engine. As a result of this the coolant degrades much faster. My experience is that it is not uncommon for the coolant to crystalize inside the system. The coolant reservoir cap contains an integrated overpressure valve. I have seen before that the crystalized coolant causes the overpressure valve to become stuck. This can either be in the open or closed position. 

I'm having similar issue on the same engine. On my own engine, everything looks fine without AC but whenever the AC is on even for just 5 minutes, the coolant will drop significantly.

Kindly provide us with an update.

What vehicle/engine do you have?

This topic is about the turbocharged, direct injected, 4-cylinder, 1.5 EcoBoost Petrol engine.


Regarding your account information you have a Ford EcoSport. I may be wrong but as far as I am aware the EcoSport has never been available with the 1.5 EcoBoost engine.
 

Well, just to update. Mechanic was useless.

Started getting a pretty rough idle and didn't think TOO much of it, then on the way home from work the other day the car started shuddering and shaking. Used an OBD2 scanner and got a 'cylinder 3 misfire' error. I changed the spark plug and coil pack, didn't get rid of the issue so I took it to a different mechanic from the last one. Was very rough to drive but only 5 minutes from home. He believes the head gasket is gone but not 100% sure, either way he's having the head removed and proper inspection. This mechanic seems a lot more knowledgeable in comparison to the last, as he straight away told me that these engines are known for coolant intrusion. My warranty from the car yard has expired and the mechanic has estimated it will be north of 4 grand (AUD) to fix providing there isn't any other surprises.

Since the original post, I stopped losing coolant or having any 'leak' signs so I simply went on as normal until this misfire error came along. The 1.5L Ecoboost is truly a piece of *****, isn't it? 

Will update further in a few days once the head is off and see what he finds.

On 10/1/2025 at 5:57 AM, niafrok said:

Well, just to update. Mechanic was useless.

Started getting a pretty rough idle and didn't think TOO much of it, then on the way home from work the other day the car started shuddering and shaking. Used an OBD2 scanner and got a 'cylinder 3 misfire' error. I changed the spark plug and coil pack, didn't get rid of the issue so I took it to a different mechanic from the last one. Was very rough to drive but only 5 minutes from home. He believes the head gasket is gone but not 100% sure, either way he's having the head removed and proper inspection. This mechanic seems a lot more knowledgeable in comparison to the last, as he straight away told me that these engines are known for coolant intrusion. My warranty from the car yard has expired and the mechanic has estimated it will be north of 4 grand (AUD) to fix providing there isn't any other surprises.

Since the original post, I stopped losing coolant or having any 'leak' signs so I simply went on as normal until this misfire error came along. The 1.5L Ecoboost is truly a piece of *****, isn't it? 

Will update further in a few days once the head is off and see what he finds.

Hi, sorry you're having this issue. I've recently experienced the same for a 2.0 ecoboost. They have a problem with coolant intrusion into the cylinders. Issue for me started seeing the symptoms at 61000, others reporting faults from 55000 miles onwards. Is your edge a US import? 

In the US Ford issued technical service bulletins in 2019 and 2022, for 2015 to 2018 ford edge ecoboost models, eventual repair is engine block replacement. 

Edited October 4, 2025Oct 4 by Rvs

Spoke to the engine shop this morning, as expected, coolant intrusion. Essentially needs a full rebuild, everything was destroyed from thermostats, water pump, head gasket and a few other bits and pieces. Main issue was cylinder 3.
 

Having the belts replaced while the head is off as well. Getting it repaired and selling it after, will never touch a ford again!