Overheating mk6 1.6 fiesta ghia petrol

[Essex fiesta]

Hi my mrs mk6 fiesta has overheated a couple of times now for some reason.

We drove it the other day for 4 miles to do a click and collect then another 3 miles to the park all with no problems at all.

We stayed at the park an hour and then drove home, but on the way home around 2 miles from the park the car overheated and lost the water out of the header tank,

We sat for 30 mins topped it back up and just as we got home another 2 miles it done it again outside the house.

The cars temperature gauge is staying normal, and we can hear the fan on the radiator coming on.

I've looked in the oil cap no sign of any white deposit, and no sign of any water coming out of the exhaust.

Could this be the head gasket or should I be looking at something else like the thermostat sticking possibly?

TIA

[isetta]

Not sure, but if thermostat stuck shut and car overheated due to that, wouldn’t the temp gauge be up the top?

[TomsFocus]

Faulty cap or header tank is pretty common.  

[Essex fiesta]

Isetta very good point, I did not even think of that

Tomsfocus thanks for that, I will try another cap and see how we get on.

Will post back up when I've got one fitted

[Essex fiesta]

Tried a new cap, topped the car up, started it, ran it up to temperature with the heater on full all the time, temperature gauge staying normal, no fan cutting in, 

Car is building pressure in the expansion tank and then losing water under pressure from the explosion tank, gauge still reading normal and fan not cutting in.

Any suggestions please

TIA

[TomsFocus]

Definitely no tiny cracks in the tank anywhere?  I had this exact fault on a 1.4 sold to me as 'blown headgasket' which just needed a new tank and is still going strong 4 years later...  Then the same on a mates 1.6 about 6 months later!  The tanks were kept in stock at the dealer as they were such a common fault.

The fact the temp gauge doesn't move is weird though.  The gauge takes an ECU feed the same as the fan, so the fan won't cut in until the gauge heads towards the red. (You can read live temp with an OBD reader if you have one)

Either you have a massive air lock so the temp sensor reading is wrong.  Or the sensor is faulty.  Or the water pump isn't working efficiently and pushing the water around.

Are the heaters as hot as they should be?  Is the radiator hot all the way down?

[Essex fiesta]

Hi Tom, 

Cant see any leak from the tank at all,

You can read the temp gauge by doing this on the car...

There is also a way to double check the sensor's readings with the electronic odometer. Key off, press and hold the trip odo reset button, turn key on, continue to hold reset button until the odometer reads [test], now each time you press and release the odo reset button you scroll through one of 30 test functions. It will remain in test mode until you turn the key off. You need to look for the one that reads [40 C] or whatever your temperature should be in C at the time. If the car has cooled overnight, then it's likely to be close to ambient temp. If it has not cooled, expect a higher reading. Drive the car in test mode. You should see your engine temp rise to about 95C, then drop down to 80 or so as the thermostat opens. This cycle will continue several times before the engine temp settles above the thermostat temperature of 92C. You should compare your findings with the test mode with those of the infrared thermometer under the hood. 

It's just really weird has anyone a way of testing the cooling system pressure with the engine cold, I'm just wondering if it maybe the head gasket between two cylinders.

To be honest I'm just guessing.

With the cap left off it builds up and then overheats out the top of the expansion tank, temp gauge normal and fan not cut in at all.

Tia

[TomsFocus]

You won't see a leak from the tank as the cracks are so small, it's more like crazing on an old china plate really.  It doesn't let any water out, just let's out enough pressure to allow the coolant to boil.  The boiling coolant then quickly builds so much pressure that the lid has to release it.

I'm not sure how accurate the dash temp test is on the Fiesta.  On the Focus it's about 40c out and no one knows why!

With the cap left off it will boil, it needs the cap on to hold some pressure in the system.

You can buy cold pressure testers that 'plug' into the reservoir, you pump them up with air and then see if it can hold that pressure or if it bleeds off.

If you suspect headgasket you can also do a sniff test which checks for CO in the coolant.  

[Essex fiesta]

Tom thanks

What's the test thing I need to pump the cooling system up, do you have a link please, 

 

As for the co sniff test hows that done please.

Also yer the dash thing works but as for accuracy who knows.

Even with cap on heater in car gets nice and hot, temp gauge stays normal, fan does not cut in i assume as the engine temps normal,  but it still boils up for some reason

 

Tia

[TomsFocus]

Just a quick link before dinner, you can get them cheaper!

https://www.ebay.co.uk/itm/312761927871

https://www.ebay.co.uk/itm/223490668138

CO2 (sniff) test is simply done by sucking gas out of the header tank with the engine running.  If there's CO2 present it'll change the fluid in the tester from blue to green.

[Essex fiesta]

Tom 

Nice one thanks for the links,

I will see what i can do

And post back

Thanks again 

[Essex fiesta]

Sorry for the slow reply,

What I've done is tried another expansion cap, this time a new genuine one, took it for a drive, car drives fine, temp gauge on car dash board is normal, 

Cadin Heater inside car blows hot when set to hot and cold when set to cold.

Really have no idea as to what the problem may be as at the moment the car is running fine, plenty of stop start traffic and showing no signs of overheating at all.

It has done exactly this before driven ok with no signs of overheating then after a stop for a while at the park about 45 mins, on the way home overheated.

As it seams more of an intermittent problem would it be possible that the thermostat is getting stuck at times.

Tia

[Essex fiesta]

Went for a drive today and all seemed fine,

then the temperature gauge shot up and the red warning light on the dash came on,

we was at our destination, so just turned the car off, 

Had a look fan was running, car was losing no water at all, header tank was bubbling

Tia

[Paulkp]

I canot offer much more help, but changed header tank on our 1.6 petrol '57 Fiesta last year as it looked like "splits" were developing, and did our '60 Fusion last week, for the same reason.  Not difficult to change, and for £20, not expensive.  

[Essex fiesta]

Hi all

Update, 

Changed the thermostat and all is ok now, 

Car is running as it was beforehand finally.

Thanks for all your info and your advice very much appreciated 

[Essex fiesta]

Final update is the car has been fine, 

Thanks again for all your help

[Essex fiesta]

Car still going fine with no overheating problem at all.

Problem was the thermostat which has been changed some time ago now, and since then no more problems 

 

Thanks all for your help

[Claire93]

Just finished reading through the comments having the exact same challenge with my ford fiesta 2004 after 2miles the water is boiling smoke coming out, bought it a month ago never used it as had to tax it first now trying to use it having this challenge been told its head gasket just so frustrated right now