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Discussion Starter · #1 ·
Hi there.
Hoping I can get some help with this issue that I'm having with my 2011 Fiesta SE with the 1.6 NA engine.
So as title states, from startup and idling for about 8 to 10 minutes, the coolant in the expansion tank would rise all the way up and start to boil within the expansion tank.
At this point, the top radiator hose would be hot to the touch, but the bottom hose would be just slightly warm.
The fan would then kick in, and stay on even after the engine has been shut off.

So what I've done so far...
Replaced thermostat twice.
Replaced expansion tank cap.
Pressure tested the cooling system and found that it would hold pressure, so doesn't look like I have any leaks.

Only thing I haven't replaced is the radiator.
Any advice, because this is really starting to do my head in.
Thanks in advance.
 

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Have you seen the cooling fans operate? The thermostatic fan switch should kick The fan on after about ten minutes of idle. If you turn on the A/C do you see cooling fan operating?
 

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Discussion Starter · #5 ·
Yes, the fan does kick in.
The first sign of something being wrong was the fan staying on for a couple of minutes after the engine is shut off.
I've been at it today, having removed the radiator and washed it out to rule out any restrictions within it.

I may be wrong, but it looks like coolant is bypassing the radiator entirely because the bottom hose stays cool to the touch.

However I have to mention that when I keep engine revs at 2500, engine temp inches up slowly until fan kicks in at 105 degrees C, cools it down and shuts off at 99 degrees C.

Doing this, the bottom hose would get just as hot as the top hose, as well as the entire surface of the radiator.

Seriously confused now.
 

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You might have a plugged up radiator. The probability of that increases if the coolant has not been changed for an extended period of time or possibly some stop leak goop was added to cure some other issue? That stuff often ends up blocking the heater core
 

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Discussion Starter · #7 ·
As stated, removed the radiator and had it cleaned out - now able to blow through it from end to end without any restrictions.

Are there any baffles or non-return valves within the hoses between the engine and the cabin heater matrix?

I may be wrong but liquids find the path of least resistance, and I think the coolant is bypassing the radiator and flowing through the heater bypass, because that gets extremely hot very fast and I'm able to keep temperatures a bit stable for a while by having the heat on with the blower at max.

What am I missing here?
 

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I've read references to bleeding the cooling system. Probably a needless question, but there's not an air pocket trapped in there somewhere that's causing these issues, is there?
 

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When you say you have cleaned the radiator and can blow trough what do you mean by that? Do you mean it was actually plugged up? Also if your radiator was plugged at some point what makes you believe that the engine itself is not or your water pump?
Also you mention it will actually flow if you rev the car, so it should take you to your water pump not working properly.
 

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Discussion Starter · #10 ·
Update:

Pulled off the water pump and there doesn't appear to be physically wrong with it.

The impeller is plastic and doesn't appear to have any erosion damage.

Still ordering a replacement, because at this stage I figure I have nothing else to lose.

Pouring water down the top hose, it pours out through the side of the block uncovered by the water pump, which rules out any blockages in the block/head.

Hope changing the pump solves it, otherwise I've got nothing else to do to it.
 

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Update:

Pulled off the water pump and there doesn't appear to be physically wrong with it.

The impeller is plastic and doesn't appear to have any erosion damage.

Still ordering a replacement, because at this stage I figure I have nothing else to lose.

Pouring water down the top hose, it pours out through the side of the block uncovered by the water pump, which rules out any blockages in the block/head.

Hope changing the pump solves it, otherwise I've got nothing else to do to it.
My second guess was a broken water pump impeller, third guess is a plugged radiator core. The coolant is obviously not flowing through the system. Being a 2011, that water pump is a good candidate for replacement soon anyways. Please keep us updated on this unusual situation.
 

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Discussion Starter · #12 ·
Update:

Pulled off the water pump and there doesn't appear to be physically wrong with it.

The impeller is plastic and doesn't appear to have any erosion damage.

Still ordering a replacement, because at this stage I figure I have nothing else to lose.

Pouring water down the top hose, it pours out through the side of the block uncovered by the water pump, which rules out any blockages in the block/head.

Hope changing the pump solves it, otherwise I've got nothing else to do to it.
My second guess was a broken water pump impeller, third guess is a plugged radiator core. The coolant is obviously not flowing through the system. Being a 2011, that water pump is a good candidate for replacement soon anyways. Please keep us updated on this unusual situation.
Initially assumed it would be the radiator too, but when I had that off, I could hose it right through.
Strange thing is, from startup, coolant flow seems to be normal, and as it warms up flow would gradually drop off in both the main circuit as well as the bypass.
Keeping the revs up above 2.5K seems to keep everything working as it should, and the moment I let off, in the time it takes me to get from the driver's seat to the front of the car, the coolant level would start to rise in the expansion tank.
 

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Another thought related to the water pump.
The impeller has been known to come loose on the pump shaft (I'm referencing general water pump, not specifically a Fiesta pump) and the shaft will spin but if the impeller is loose, the impeller will spin slower than the shaft and could cause overheating.
 

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Discussion Starter · #14 ·
Update:

Changed the water pump and no joy yet?

Still looks like somehow coolant is not moving around; sitting in the block until its brought to a boil.....at this stage, I got nothing else.
 

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Discussion Starter · #15 ·
So starting to look like the engine might be toast. Started to overheat again even with the thermostat removed.

The entire surface of the radiator gets hot in time, but I constantly have gas/steam purging from the bleed port at the top of the radiator.

Have tried bleeding the system multiple times by filling it from the top radiator hose as well as tried vacuum filling it with a vacuum pump, but still made no difference at all.

Starting to think I may have a crack somewhere in the head that's pressurizing the coolant or causing it to boil off inside the engine
 

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I had a previous car that had bubbles in the overflow tank. It was the head gasket leaking exhaust gases into the engine coolant.
 

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I had a previous car that had bubbles in the overflow tank. It was the head gasket leaking exhaust gases into the engine coolant.
I'm just catching up here, and was starting to think the same thing. I've heard of bad head gaskets causing similar issues over the years.
 
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