Hello, I’ve noticed that the hot air coming from my Fiesta isn’t as warm as it used to be. Additionally, when I check the engine temperature via OBD after about 40 minutes of driving, it doesn’t go above 60–65°C.

I suspect the thermostat might be stuck open, but there are no related DTCs.

Can you confirm the standard time it should take for the engine to reach 90°C, considering the outside temperature is between 0–5°C?

The water pump has just been changed with the belts, so as the coolant.

With an outside ambient temperature of 0-5^oC it might never get the engine temp up to 90^oC no matter how you drive.

All modern engines are a lot more efficient than what they were 10 or 20 years ago and don't produce the vast quantities of waste heat that older engines used to do.

I have a 2.0 Ecoblue and during cold weather it never makes it much past 60^oC

45 minutes ago, unofix said:

With an outside ambient temperature of 0-5^oC it might never get the engine temp up to 90^oC no matter how you drive.

All modern engines are a lot more efficient than what they were 10 or 20 years ago and don't produce the vast quantities of waste heat that older engines used to do.

I have a 2.0 Ecoblue and during cold weather it never makes it much past 60^oC

Actually I never remeber it getting near operating temp even when outside was 10°C and the engine at a costant 4k rpms on the highway. I should find a way to check if it can heat up that much, or for instance to check if the thermostat is working correctly.

Whilst 0-5^oC might be 'a bit nippy' for us, for a car engine it not that low an ambient temperature and so the engine should definitely still be reaching full operating temperature. Sure, it might take longer if the engine block has to warm up from that temperature but should still be doing so once under load. It's not really about engine efficiency - the exhaust gases alone will always be several hundred degrees regardless, and the jackets around the cylinders through which the coolant travels will be considerably higher.

A stuck-open thermostat could be the issue, but I wouldn't necessarily expect that to inhibit the max temperature of the cabin heater as even at 60^oC there's still plenty of heat capacity to give a good roast, and once you've stopped moving after a good run there's no additional cooling from forced air flow through the radiator and so at a standstill any excess heat can only be lost through the cabin heater (until the radiator fan cuts in of course, but that won't be doing so at only 60^oC).

Given the mention of a recent pump and coolant change I'd be learning more towards an air lock or insufficient coolant fill in the first instance.

I plugged in the OBD scanner and monitored the temperature while driving. It was a 40-minute trip with no traffic stops, just steady driving. The outside temperature was 7 degrees according to the weather app, but the car showed 3 degrees.

After idling for 5 minutes, the car reached around 20 degrees. Once I started driving, after about 15 minutes, the temperature climbed to 31 degrees and then stopped there. For the rest of the trip, it stayed stable around 31, occasionally hitting 32, but it never went any higher.

On the way back, I let the car cool down for about 2 hours at the outside temperature. After another 40-minute drive, the temperature at arrival was 42 degrees.

1 hour ago, MJNewton said:

Given the mention of a recent pump and coolant change I'd be learning more towards an air lock or insufficient coolant fill in the first instance.

I’m not sure how to check for an air lock, but I’ll definitely look at the coolant level again. I had checked it after the work was done and it seemed fine, plus there are no leak marks on the garage floor, so I think it’s still okay. But I’ll take another look to confirm.

The coolant level is slightly below the MAX mark.

Today, I let the car idle in my garage for about 10–15 minutes, during which the temperature rose to 70°C. However, as soon as I started driving, the temperature quickly dropped to 41°C within about two minutes.

I also touched the hose connecting the thermostat body to the radiator, and it felt very hot. From my understanding, coolant should only flow through this hose when the thermostat opens, which typically happens at temperatures above 91°C. Is that correct?

 

 

1 hour ago, mattuz said:

I also touched the hose connecting the thermostat body to the radiator, and it felt very hot. From my understanding, coolant should only flow through this hose when the thermostat opens, which typically happens at temperatures above 91°C. Is that correct?

 

It's not quite a cliff-edge and so will begin to proportionally open somewhat before that. The top pipe shouldn't be hot (warm perhaps as there might be some bypass depending on the layout of the cooling circuit) whilst the engine is still warming up though as this will be well below the point at which it should start to open.

The fact your coolant temperature is dropping only when moving does point towards a stuck-open stat.

48 minutes ago, MJNewton said:

The fact your coolant temperature is dropping only when moving does point towards a stuck-open stat.

Well, at this point, I’ve decided to order the part since it’s inexpensive (I plan to replace only the thermostat, not the entire housing).

Regarding the replacement, I’m considering removing it without draining the entire system. The reason is that the bottom hose is inaccessible without removing the engine splash shield, and I don’t have the equipment to lift the car and take it off. Do you think disconnecting this hose will result in all the coolant draining out, or just a small amount? I’m assuming it’s mounted high enough that only a little might spill.

Hopefully, by removing the air filter box, battery, and battery box, I’ll have enough space to place something underneath to catch any spilled liquid. I need to remove those parts anyway for other stuff.

 

Whilst I am not familiar with this particular engine, thermostats are generally found fairly high up in the system so coolant loss will be minimal. I'd expect it'll still need a top up though. 

One thing to note is the orientation when it comes out. There is usually a small jiggle valve at one point around the edge (it lets trapped air through to help avoid air locks) and this should be positioned in whatever position it is designed to be - usually uppernost - and so keep an eye out for that on the original and put the new one back in the same position. This strategy assumes of course that the one in there has been fitted correctly! 

i may be able to shed some light here,  a diffrent engine but, same thing was happening with my 1.5 diesel.

i had a slight coolant leak from the thermostat gasket shrinking, and it would take a while blow any warm air, when my coolant dropped in-between max an minimum.

like you i tested it with the obd2 port with a scanner and it stay around 60 degrees this was parked without no cold air being forced through the grill, so driving it will only make it cooler with air movement. i checked the thermostat off the car when replacing the gasket and it opened.

now after a flush i had too hold the revs of the the car for almost 30 mins get up to high temps watching via the scanner at 2.500 rpm and short bursts of 4000 rpm until the fan kicked in that will then burp the system.

this is what i observed whilst doing a coolant change now the coolant is at max it warms up via blower fast but on minimum it took a while.  

The thermostat was indeed stuck open. After replacing it, the engine now quickly reaches its operating temperature and maintains it very steadily. Thank you, everyone, for your suggestions!