2011 Fiesta 1.25 overheating

[smokieuk]

This (my daughter's) car has been with my mechanic a number of times for this problem but we've not yet fixed it. it looks remarkably like problems reported on older Fiestas caused by a faulty heater control valve, but I'm not sure my car has one - certainly can't see one in the engine compartment, as per YouTubes...

So the symptoms. Firstly, the car will sit idling for hours without overheating, The fan kicks in correctly.

My mech plugged in his device today so I could drive for a bit and test extensively. In short:

• It is definitely overheating - warning light comes on at 120 degrees.
• If you then turn on the cabin heating it drops fairly quickly back to about 102 (this is on motorway driving) and stays around there, or a bit higher.
• Mostly the bottom radiator hose does not get even warm during/after driving, but after one test today I left it idling with heater and blower on full for about 10 minutes (temp about 100) - temp dropped to 90.and both rad fans were pretty hot.
• Both of the heater pipes were hot each time I checked them.
• The temp change when turning off/on the heating when running at 70 mph is entirely reproducible.

The car has been in the family since it was 6 months old and it has never had any parts replaced or gunk added to the coolant. It has about 45k miles and FSH, mostly Ford. It used to be the wife's car so no-one will have driven it hard.

So far it's had a new radiator cap and fan (which wasn't working, as tested by an automotive electrical engineer!). it's been bled and the mech used a sniffer and said there was no evidence of head damage. The coolant levels aren't going down. He advises that the pump appears to be working, the rad doesn't appear to be blocked and the hoses all seem OK.

So we are stuck. Having read other threads I've asked him to replace the heater control valve but as above, I'm not sure it has one (though I feel it must).

If that doesn't work I guess it will be a water pump then a radiator, but there is nothing else we can think of. I am trying to limit the cost too!!!

Any thoughts would be much appreciated. Either about HCVs, what to do next, or other diagnostics/tests I can do to narrrow it down.

[smokieuk]

I missed that a sensor has also been replaced.

[isetta]

has it had the thermostat replaced?    

In the old days if a car suffered from overheating the first thing to do is to remove the thermostat. Having no thermostat normally means much longer warm up which is bad if you need heat to demist windscreen (in winter) but not so bad this time of year.

Also an old problem was radiators silting up. the channels in the rad went top to bottom, these days they go side to side so that might assist in stopping total silting up. people would remove radiator from car and backwards flush it with hose / pressure washer (not sure how tolerant the rads are to pressure wash).

I do not know how it has been established on yours that there is no rad blockage.

I do recall someone on here having problems and it turned out that the impeller had broken off the water pump shaft. you say water pump seems to be working - I am not sure how that has been established but I tend to think it probably is if using heater cools it down.

If having heater on helps cool it down and the rad fans come on it does make me think it is main radiator blockage or the thermostat is stuck shut. 

But I would have thought thermostat is first thing that would have been checked.

Another thought - unlikely but worth checking - you say fan replaced. I do not know if it is possible to fit the fan backwards or connect wires round wrong way. That would make the fan suck air from engine bay and blow it forward out of the grill. That might work well when stationary but when moving the movement of the car forward with the fan blowing forward would cancel eachother out and there would be no airflow through the rad.  Sounds unlikely but you have got to check that.

also make sure there is nothing stuck on from of radiator like some polythene debris stopping air passing through it. In the old days people sometimes stuck some card etc over front of radiator to make it hotter in winter. 

[smokieuk]

Thanks for the response.

The guy doing the work is an old-fashioned mechanic and is usually pretty thorough and trustworthy. The thermostat was the first thing replaced. I don't know how they established the rad wasn't blocked, I can go back and ask (next week). I was there when he and another mech determined that there was unlikely to be a problem with the pump - I think this was as the water surface in the expansion tank was a bit choppy on tickover!

The fan was the second thing replaced as it was determined (by an auto-elec tech) it wasn't working correctly. I'd be surprised if it can be fitted or wired backwards.

There's nothing stuck on the rad that can be seen...

Of course this isn't all entirely technical but I am trying to keep the bills down for my daughter!!

I am also of the opinion that it is thermostat related. What I want to understand is how the water flow goes, as other on problems I've read about the water reaches the stat from the heater element, so if the heater valve is duff then the hot water never reaches the stat so it doesn't open. Therefore the water doesn't flow through the rad and therefore the bottom hose never gets warm (except once when it had been standing idling a while).

I'd welcome any other comments but next week's plan is likely to start with changing the stat again (cheap option!) after asking the questions you've raised. I think after than it will be chaneg the pump, then change the rad. And that's it, out of ideas after that!!

 

EDIT: removing the stat completely might be an idea, I'm just not sure what that would prove. I think if the bottom hose got warm it would be proving that the stat is faulty or is not being triggered. But that's what I'm already veering towards.

[smokieuk]

I forgot to add my daughter has also reported the aircon isn't blowing cold. Another thing which led me to the heater area being the issue. I know they are different bits but the cold air comes out of the same vent so if the heater valve wasn't fully operating then the cold air from the aircon would be contaminated with hot air from the heater.

I'm good at making up red herrings so feel free to correct me where the logic is wrong!!

[isetta]

I have no idea how easy it is to get the thermostat out but if it was mine I reckon I would take the thermostat out and see what happens then . in the old days you could test a thermostat by putting it in a saucepan of water on the cooker with a thermometer in and see the temp when it opens. I do not know if modern cars still have this same style of wax capsule thermostat. 

[smokieuk]

I'm back from a weekend away, and I need to see my mech this afternoon.

I'm going to suggest removing the stat but would appreciate a bit of clarity on the expected outcome and what it proves. 

Has anyone had any further thoughts? Seems the 2011 Fiesta does not have the same heater control valve as the earlier ones which have been problematic.

[smokieuk]

Just been over to see the mech. The thermostat is under some pipework and isn't that accessible. He's sure it is OK though - it is, after all, new.

Tomorrow he's changing the radiator. 

[smokieuk]

New radiator did not cure it. So far the following have been changed/checked:

Fan 
Thermostat
Sensor
Filler cap
Radiator and bleed cap

Other info

Car is only 2011 with 45k miles
Sniffer in coolant tank indicated no head problem
Water is "active" in tank which makes them deduce that pump is OK (at least at tickover). 
All pipes seem to get pretty hot except bottom radiator one which remains almost cold (all being to/from cabin heating, top rad, connected to engine, back to coolant tank)
Temp reduction when cabin heater turned on probably a erd herring as it rose after use in that state
Aircon is not blowing v cold
No visible obstruction on front of aircon "radiator" (which sits in front of the coolant rad)

The bottom pipe is still not getting hot which indicates to me no water circulation. Seems to me only the pump left. And hoses. And do the thermostat again.

Can anyone suggest how best to determine which to do next? It's getting rather expensive now!!

[smokieuk]

Isetta you'll be pleased to know that swapping the Eurocarparts (£7) thermostat for a Ford (£23) one appears to have fixed the problem.

I tested the Ford one before fitting and the other one after it had been taken out and both passed the saucepan test.

The fan was deffo broken so I am somewhat out of pocket really for a radiator and an additional thermostat fitting cost. In the old days I would have done the thermostat myself but this one is at the bottom of the block and requires removal of the alternator and draining the coolant so I had to pay to get it done.

Thanks for your interest.

[isetta]

Thanks for posting the final outcome. There are so many threads on this forum where we never know what the final result was.

Very little is easy on cars these days. a 1960s cortina was somewhat easier. you opened the bonnet. The thermostat cover was right there in front of you, two nuts and it was off.

[smokieuk]

My third car was a late 60s Cortina :-) The first two died awful quickly though, so I'm not as old as that might make me sound 🙂