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Temperature Gauge Going To Red

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2004 1.6 Ford Focus Zetec. 43k Miles.

On prolonged/consistent speeds of 40-70mph the temperature gauge will go to the red. When i come off the accelerator or come to a stop the temperature gauge will go back to the centre. On this particular day the weather was hot and the aircon was on near full (If this is relevant). All fluid levels are fine and there has not been any drop.

Replaced: Water pump, thermostat, head sensor (?). I've been advised now to replace the 'fan cowling resistor/sensor'. .....

I know details are vague but ask and ill try to answer if you need more details. Do you think this will fix it, other than a blockage in radiator what else could it be. I have read that the fan cowling sensor wiring can become damaged and he fan will kick in when the temperature is in red, but i dont know for sure if i have this problem (The car is not with me at the moment).

How do i find a fan cowling resistor/sensor for this model ? Im finding it pretty difficult. Is it called something else ?. Ive heard that Ford only stock the whole thing rather than parts.

Any advice is very welcome.

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I would start by draining the system and flushing it all put before refilling/bleeding - given hat you have changed so far

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The reason the engine gets hotter when the AC is on is the AC sucks the hot air out of the cabin and dumps it in front of the radiator - heating up the air entering the radiator

The heat sensor for the fan is in the cowling - look for wires/ connectors - the connectors can often get corroded and cleaning them up might sort it

You can go for months with no (apparent) problems then when the weather gets hotter the engine overheats - the AC compounding the issue - it may be that all that is wrong is the fan is not coming on and this has been a long- term fault

Try to find out as much as possible - does the heater get hot? does the fan ever go on? check how hot the hoses get

As an emergency, you can turn your AC off, then turn your heater up (full hot/ fan high) - this will help cool your engine as the heater can act as a secondary cooling system - you can open the windows and direct the heat out of those vents - next time the engine overheats try this and see what happens

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most of the radiator fans works in two stages, first at low speed controlled by the air con, to cool down the condenser radiator, and the second stage is controlled by engine temp, to test the fan you can make a test lead with a in line fuse connected to the battery, this is what I did on my focus, the fan had failed. (If your car as two radiator fans check both)..

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Hi, let the car tick over without the A/C on until the fan comes on, then look at the temp gauge. If the fan doesn't come on it is probably the fan sender sensor or a relay/fuse...

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Thanks for all the advice, i really appreciate it. Ive just come back from a ford dealer, and they reckon its not a fan/motor/connector issue, they said theyve not even done one or ordered one. He said check for an airlock.

Im not ignoring anyone but seeing as a few have responded im kinda replying to you all here. Its a single fan twin speed i think. I let the engine tick over around 2 revs for 5 minutes, i didnt see the fan kick in, the temperature gauge didn't change though ?. Should i rev at a higher level ?

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Hi, on tickover it would need longer than 2 mins. No harm in increasing the revs but be mindful of your neighbours and noise though...

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Start your car, turn air con on, the fan should run in stage one right away, if it don't then the fan is prob us, test it with a made up lead from the battery, if the fan is ok will run at full speed.

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Before spending any more money on it, try changing the expansion tank cap. If its not sealing properly it will cause the symptoms you have as it will restrict the circulation due to lack of pressure.

The cap should be changed regularly anyway and rarely is.

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Sorry for the delay in replying. Here are some updates.

Starting the car from cold. It takes roughly 3 and half minutes for the temperature needle to centralise. Revs start around 1200 and slowly come down to around 500. When i first got the car, revs were practically nothing and the temperature gauge centralised very quickly.

I took it to a garage, they told me its a crack in the head gasket or cylinder head. There are no signs besides over heating. There was power loss and juddering once, however i read in the hayes manual there is a fail safe cooling system. So the engine will run on two cylinders, and restrict revs. Could this be the cause for apparent power loss, and juddering ?. They quoted me VAT + 600 for the head gasket, and 200+ for the cylinder head too. Quite frankly im not paying that, and unsure if thats the real issue. I can have the head gasket fitted for practically nothing, however i am reluctant to change it if its not necessary of course.

I took it back to the place i bought it from. Quite naturally they are reluctant to do anything with it, dragging their heals. And insist its an electrical problem rather than head gasket. They insist if it was a head gasket, the coolant would be !Removed! out, temperature gauge would be constantly red, very rough engine etc. To be fair they have a point i suppose, because i havent really experienced any of this apart from periodic red temp gauge, engine loss of power and juddering once, although the engine revs from cold and general sounds whilst running idle doesnt seem perfect. They are persistent with saying its a sensor or electrical problem, and almost completely discount the head gasket/cylinder head.

Firstly i just want to clear something up. In the hayes manual, they phrase 'cylinder head sensor'.... However looking at parts websites, it appears to be phrased 'Coolant temperature sensor'. I cant find cylinder head sensor on any part sites for my car. Are these the same thing termed differently ?, or does my car have a coolant temp sensor, and a cylinder head sensor. The coolant temp sensor on the websites are identical to the old 'cylinder head sensor' that has been replaced. http://www.gsfcarparts.com/929fo0280 This is the part that was replaced, so the cylinder head sensor and coolant sensor are either exactly the same or theres two. The ford part numbers match as well.

In regard to the fan. I have a single fan twin speed. http://www.mister-auto.co.uk/en/radiator-fan/bolk-bol-c021076_g508_a999BOL-C021076.html This by the looks of it. After driving and coming to a stop, the fan seems unusually loud, maybe this is due to sensors or signals telling it the engine is hot. When starting from cold, the fan does not start, i tried what people suggested: turning the aircon on and seeing if the fan comes on, and it does. I have not tested via battery method yet, which i assume forces it to run at top speed, and if it doesnot its broke. But the fan does appear to run at full speed because when coming to a stop after driving its extremely loud.

The coolant appears to be circulating well, when you go up the revs, the flow increases. The pressure in the expansion tank doesnt seem to be all that great, however im not losing coolant.

What can i try from here ? Any suggestions ?

Is there anymore sensors i can change ?

Anything electrical ?

Should i take it to another garage for a second opinion ?

Would it be worth doing diagnostics again, if its a head gasket diagnostics wont register it though ?.

The fan does appear to work ? So is there any point replacing it.

Thanks

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Ive just been faffing about with it.

I started the car from idle, left it running for 10 minutes or so. I started to squeeze the coolant pipes, coolant would flow into the expansion tank each time i did it. The revs and engine seemed to slow down to a normal level very quickly.

The radiator was cold, where the thick pipes (top and bottom) enter the radiator they were also cold for probably two hand widths down the pipes, but then quite warm beyond that.

Can we read anything into this ? Or is this quite normal ?

I suppose i would need to drive the car for a while to find out if the radiator and pipes near it are getting warm as well.

But if rev the car whilst idle, the coolant does flow into the expansion tank, so would this rule out an airlock ?

When i just turn the key over without starting, the engine and oil lights come on but disappear when i start the engine.

:ph34r:

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First of all let me explain i really only know about Mk3 Mondeos - mostly diesel ones

Ok, About the temp sensor - on the mk 3 - it is in the head - this is true for many modern cars - the main advantage is if the car runs out of coolant or it runs low - the sensor will still work - even if the coolant runs dry - if the head gets too hot, at a pre- determined temprature the ECU may cut the fuel/ power or go into limp mode - to protect the engine

The other advantage of having the temp sensor in the head is that the head can cool down after the sar has been sitting after a run and the coolant is still hot - so the ECU "reads" the had temp rather than the coolant temp - and the temp gauge reflects this - "knowing" the actual head temp helps the ECU to adjust the fuel/ air ratio and timing more accuretely for better emissions and economy, its the head/ engine temp that is important, the actual coolant temp is less important (untill the coolant cavitates or boils! )

There may be 2 more temp sensors - the IAT (intake air sensor) and the outside temp sensor - both connected to the ECU

Here is some stuff you should know -

Pressurization of the coolant system is to raise the boiling point - at normal pressure water boils at 100 degrees centigrade - under pressure this is raised to about 110 degrees centigrade, the expansion tank cap regulates this pressure, along with the sealed system

Antifreeze also raises the boiling point of the water/ coolant - different types/ concentrations of anti-freeze have different boiling points

in developing/ redesigning the cooling system on my car i de-pressurized the cooling system to put less stress on the (expensive) electric pump, the type of anti-freeze was changed to raise the boiling point to near 119 degrees centigrade

-----

The waterpump is mechanically driven, it is a centrifugal impeller that always turns when the engine is running - it runs proportional to engine speed - when the engine starts it starts circulating the coolant, even when the engine is freezing cold it feeds the waterjacket on the side of the block - the waterjacket is like a second scin on the engine - like a container outside the engine - that the coolant circulates round - the coolant exits at the top in the head - where it goes 2 ways - before the thermostat opens, it goes only to the small hoses to the cabin heater, there may be a bypass valve - to bypass the cabin heater matrix - the small hoses come out of the heater/bypass valve and run under the engine back to the waterpump

So when the engine is cold the thermostat is closed so the coolant does not run through the large hoses or the radiator - it just circulates through the pump, into the waterjacket, through the small hoses to the heater matrix and bypass valve, under the engine and back up to the pump

As the engine warms up, the bypass valve closes at a pre- determined temprature - then all the coolant runs through the heater matrix - this happens at a lower temp than the thermostat opening - on a very cold day and/ or the engine does not produce any heat - the thermostat may not open at all/ the heater may take more heat out of the system and the engine may run cooler than its operating temprature - the heater can thus be considered a secondary/ backup cooling system for the car

Say its a hot day and the heater fan is off - the water circulates as above untill - at a preset temrature, the thermostat opens - when the thermostat opens the water is allowed to run through the "fat" hoses and through the radiator, it goes in the top and out the bottom, so it is hot at the top and cool at the bottom, it gets fed back to the pump and circulates round again.

because the thermostat is open, the radiator cools the coolant, so the coolant temprature drops, after it drops to a certain temprature, the thermostat closes, which stops the coolant from running through the radiator...... because the coolant is not running through the radiator it heats up, causing the thermostat to open..... and the cycle repeats

So the thermostat opening and closing maintains the correct temprature

So the temprature rises and falls slightly as the thermostat opens and closes

And the radiator hose stays cool before the thermostat opens, as the engine warms up and the other small hoses are warmed

And the radiator hose going into the radiator geta much hotter than the one coming out (just the radiator doing its job)

-----

With the AC off- the fan only comes on at a (realatively) high temprature (higher than the thermostat opening temprature) - on many engines it is off or on - it does not vary in speed

it is often controlled by a simple thermal off/on switch in the cowling on the back of the radiator

The most likely time the fan comes on is after a hard run, on a hot day, sitting in traffic with the engine ticking over

this is because, because the mechanical waterpump is proportional and the engine is running slowly - the pump is running slowly too - so the coolant is circulating slowly round the system, there is no airflow through the radiator, so when the thermostat opens it does not cool the coolant much running through the radiator, the coolant temprature rises untill the fan comes on - but once the temprature has got that high its difficult to cool down again - especially when the car is stationary and the engine ticking over (so the waterpump running slowly)

Other potential problem areas are going uphill at lower speeds or towing/ under a heavy load etc

Although the fan comes on when the AC is switched on, the AC still dumps hot air in front of the radiator

The radiator relies on the temprature differential (drop) to work - so if the car was in the desert (death valley?) and the ambient temp was 100 degrees C, the radiator could not cool the engine to below that temprature - (exept for the chill factor of moving air) nevertheless the cooling system is very dependent on the ambient/ atmospheric temprature - it makes a big difference - once the weather gets colder the car may not overheat anymore

It may just be something small like one of the blades on the pump has sheared or there is a blockage in the radiator or the thermostat is sticking etc - reducing the efficiency of the system - it sometimes does not take much to "tip it" - maintaining the temprature is a fine balancing act

In my opinion, I would be surprised if the head gasket is blown

Sorry about the long post - i learnt far, far :lol: too much about these things in doing the electric pump conversion

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Bumping this.

Dad has a 1.6 petrol 2013 focus and says the temp gauge is showing 3/4 when just driving small distance, would that be normal?

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IDE replace the coolant expansion cap first you'll be amazed how many supposed head gaskets were fixed with a part costing a tenner

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Apparently it sits at half but he said it goes to half within 30 seconds of starting it up. I said it's probably cause the engine was still warm from being driven earlier.

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