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04 Focus - Temp Sensor In Red & Loss Of Power - Electrical Problem?


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Hey guys ford nooby here!
Recently brougt a ford focus lx - 1.6 petrol - 48000 mileage - 2004 reg

car was working fine then i had it serviced including radiator flushed out with radflush & new anti-freeze.

At first car was fine but on the motorway the temperature warning light appeared & the needle jumped into the red.
No pressure or water loss but the needle kept on jumping from halfway in to the red (but never below halfway).

Local garage who gave it the once over & eliminated the following: blocked radiator/water pump/air lock/radiator fan working
heaters blow hot air, no pressure or water loss except two main water pipes once is hotter than the other.

Following day after a 20 mins drive the temp light appeared again, needle in red & engine management light appeared which triggered the engine cut out safety feature; so the car would stop accelerating.
3 codes appeared - P0420 catalyst system/ P0340 camshaft position sensor/ P1299 manufacturer control - all codes cleared.

Back to the garage who changed the water/temperature sensor (orgional ford part) & thermostat - result: car stopped cutting out
but temp needle still jumps in to the red after 20 mins & going above 50 mph - ish

i dont have much money left to spare & i im not too confident the mechanic can sort the problem without bankrupting me! I would apppreciate any help from you guys

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is the water temperature actually rising, or is it being suggested that its purely an electrical issue.

also, does the power still drop [though not cutting out] since stat and sensor changed

if car is actually overheating, could be a blockage, small blockages often only become apparent at speed.

if overheating and losing power still, could also be a blockage in the exhaust system/collapsed catalytic

if its an electrical issue..number of possibles, but i would start by thoroughly checking the charging ststem, though if this was the case would expect to see symptoms beyond just the temp guage...would also thoroughly check for shorting in the temp sensor wiring.

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the power is not dropping anymore after the sensor & thermostat changed.

what does the charging system consist of that you mentioned so i can ask the mechanic to investigate?

also are you thinking there maybe a partial blockage in the radiator?

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that depends if the engine is actually overheating or wether its just an electrical issue

if overheating, yes i would say its a blockage

what i meant by charging system, is if its electrical issue, it could be that the alternator is way overcharging the battery which will affect the guage, but would also expect it to cause other electrical issues...

if its electrical issue, would more likely lean towards a short in wiring for that sensor

the fact the power is no longer dropping would eliminate an exhaust blockage

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ok so should i get the mechanic to replace the wiring if its possible? or is there a way to check for shorts in the wiring?

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beyond a physical check of the wiring, not a lot to test for unless you can replicate the problem with head under the bonnet

think you really need to find out if the engine is actually heating up or not first, im leaning towards it is, purely because the stat change appears to have improved matters slightly.

does the temp guage rise just as high now, as it did before the change?

to give an idea what a blockage can do...shall relate a similar tale......are you sitting comfortably :)

had a 07 passat come to me with similar problem....could drive around town all day, but soon as it got up a bit of speed, would try to overheat.

done the usual stat, flush, etc, etc...but still kept happening.

ended up going to dealer for drain/flush/refill using a vacuum system which supposedly got rid of any air locks etc.

well that made situation worse...i ended up stripping the cooling system bit by bit, flushing and cleaning everything as i went...eventually came across a by pass hose that allowed water to the top hose from behind the stat..within that by- pass hose was a very small restrictor valve which was blocked solid with metal that is often found in leak stop additives..that then led to me removing the radiator, which i then had to butcher..i had flushed this rad many time over, but it wasnt till i literally cut the rad in half, did i find two of the bars blocked solid with leak stopper...would never have picked up those bars were blocked in normal circumstances as rad fely hot throughout when stat was open...but those combined blockages were enough to cause the problem.

new rad, cleared hose and alls been well since

so you really need to find out if engine is actually heating up or not...with all the work you've had done, if it is heating up then i think you have a blockage or even a very small head gasket problem

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looks like i may have to take it to the dealer to get a definitive answer on the what the problem is.

the temp gauge still rises to the same level as before but no power loss or warning lights have returned, i will be taking it on the dual carriageway to see what happens if the gauge stays in the red for a while to see if i have power loss as before.

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have you tried replacing the coolant cap? if its faulty you wont get enough pressure in the system to stop the coolant boiling therefore it will show the car is over heating when its not usually after a time once the thermostat has opened and hot coolant is pumping through

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just to update:

i took the car to the dealers for a diagnostic for £80.

They told me the datalogger they used had found historical fault codes (the ones i mentioned from a approx a week ago) stored on the ecu & had cleared them. they had the car running in the workshop & no signs of engine overheating therefore they did not carry out a pressure test for head gasket damage.

they also mentioned the temp sensor & thermostat all working.

so after i had picked up the car what happens the same problem as before! the temp gauge in the red after a 20 min drive. i did ask what if the problem reappears & was told then this strongly indicates a fault in the water pump or partial blocked radiator.

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I did find this post on honestjohn, anyone come across this before? i might give it a try as it seems to be the cheapest option :

Ford focus 1.6 Zetec - Thermostat jumping to red and back again - Grimps this is my post on another thread which may help
I am posting this in the hope that I can save others from expense of going through what I have. If you want to just skip to last para the solution is there. Over the past month I have had the same probelms with my 2001 Focus 1.6 Zetec. I have owned the car from new and various members of the fmaily have used it so its taken 11 years for this issue to come out. The temp gauge would shoot to the red mostly when on a motorway or climbing a long hill but it gradu

Cut a long story short, change thermostat, then temp sender, then full flush of rad, then had water pump examined by camera, then garage found that head was an issue when tested at high tempertaure as gas was discoulouring test liquid they used. Head was warped probably due to overheating.

After rebuild no better so garage spend hrs on the interent to find solution (I had tried and not found one). like above everyone says they have an issue but no one says what the solution is!!! So thanks to my garage (an independent) here it is for those who feel there is no end to the problem.

ally got worse to the extent that even on short journeys it was an issue.Ford in 2001 issued a bulletin on overheating 1.4L and 1.6l Zetec engines. Bulletin TSB 005/2001 which was updated by bulletin no.5 dated 17th may 2001 (1 month after I bought the car). The fix involves new expansion tank and cap, new 74degree thermostat and new coolant hoses to splice into exisiting. Thanks to my indepedent garage they found this - when they spoke to Ford they knew nothing but went and investigated and parts were delivered in 24hrs once they had agreed it was the fix. Ford should be ashamed of themselves for not informing drivers better as there many many drivers out there who seem to have the issue but no one seems to know the fix. Hope this helps, my car to date has not overheated despite my best efforts in testing the garages work.


Hello, just read this thread on the overheating focus, its very interesting and I am just wondering if you have had overheating since.

The reason I ask is that I have a suspect head gasket failure on my 02 focus 1.6 auto, but I have no tell tale signs (oil in coolant or coolant loss) just overheating after a short journey and major overheating over 60 mph.

All this seemed to happen after a coolant change, I found a crack in the thermostat housing so I replaced it along with the thermostat and bled the system, it overheated. I have bled the system several times since but with no luck, it still overheats.

I was nervous about driving it while overheating so I decided to run the car with the thermostat removed and to my surprise the coolant circulates freely and does not over heat.

The car has only 67,000 miles on the clock and before I pay £500 on a new head gasket I thought I would have a go at the coolant mod, any advice or pictures would be greatly appreciated.

Regards Patrick

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testing for a head gasket is quite straightforward with the right equipment....for the life of me i dont understand why this test wasnt done at Ford at the same time, with the knowledge of the symptoms you have given them, thought it would have been a glaringly obvious test to make. ????

with regards to above bulletin, not come across or heard of this before, but would probably find that because yours is an 04 anthe bulletin is dated 01, chances are that your engine wouldnt any longer be affected by the problem.

worth taking for a full head gasket test, but im still leaning towards a blockage, especially if no water loss apparent.

a water pump fault is a fashionable diagnosis for this kind of fault, but is very rare unless the blades on the pump are plastic...dont believe ive seen a ford with plastic impeller...though for peace of mind, might be worth a check

quick question...are you aware of any work on the cooling system prior to the problem, in last few years? if so, what was done

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No im not aware of any previous work on the coolant system as I only had the car 4 weeks now, i have fitted a new water tank cap from GSF car spares but no change.

I'm going to ring ford & ask for a pressure test to be done free of charge considering they all they did was clear out the fault codes, which was done previously.

And considering all the symptoms I described they should have performed this test, when I asked why they didn't I was told because the engine was not overheating while it was running in their workshop ( but the temp dial only jumps in to the red at high speeds)

ive been told there are two temp sensors, one for the cylinder head & one the fan. when I checked on GSF all they had was a FAE radiator fan switch. do you guys think its worth replacing this?

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if fan isnt kicking in, would tend to overheat whatever speed your doing, at speed,you have the extra air flow going through the rad so fan will kick in a lot less than in traffic for eg.

you can just run the engine to temp then with the bonnet open, check to see if fan kicks in before temp starts to rise too high.

one test you can do...run up to temp, turn the heater on and set fan to mid speed, keep engine ticking over and see if the air from heater stays at a fairly constant temp, if you notice the air cools noticably after a few minutes this would indicate the water isnt circulating correctly...

im still thinking its a blockage, if it is, put money on some kind of leak stop is causing it....but well worthtaking back for a HG check

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the fan does work but I have notice when driving locally & when the temp jumps in to the red the fan will kick in straight off & then the temp will go down within minutes.

with the heater test you recommended is that with the heater on hot or cold?

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i have tried the heater test you suggested but the temp does not drop.

having spoken to ford again they wont do a pressure test without me paying for it any way they said they had done an electric test an all the switches seem to be working fine & its a flow problem. therefore without stripping the engine they cant investigate. if they was to they suggested the water pump would be looked at. if the water pump is replaced would I need to replace the cam belt or alternator belt also?

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dont you just love main dealers...charge you 80 notes for a overheating diagnostic, but apparently a cooling system pressure test and head gasket sniffer test would be extra :rolleyes: couldnt make it up

so taking this back a bit....car overheats at speed....electrics have been given all clear so causes can be any of following

1/ air locks/blockages/flow problem...most likely

2/ brakes binding/clutch slipping...unlikely as this will show up as loss of power, which you seem ok with...but worth a check

3/ blocked exhaust...again unlikely, as once again this would show up as loss of power too...but worth a check

'stat has been changed, cap changed, not losing water,

suggest you run it up and make a note of when the fan cuts in, anything later than just above halfway mark on guage might indicate the fan switch is struggling, can also mean stat might be faulty too, so do a physical check of all the hoses to see if all are hot

next it would need a sniffer test for a head gasket problem, shouldnt be expensive as its a fairly quick test that most garages would have the equipment for...just be specific about what you want them to do..ie.. sniffer test for combustion gasses in cooling system


if all the above pass with flying colours, then i think the cooling system needs stripping bit by bit and give it a thorough check and flush as you go along, this should include removing the pump and check the blades, probably a good starting point.

the fact that the heater doesnt seem to lose temp, then would be fairly safe to say that there is no blockage there.

remove all hoses and check for blockages paying particular attention to all the smaller bore hoses and their connections.

the radiator is very difficult to confirm that all is clear, at minimum, suggest its removed and flushed both ways whilst keeping a close eye out for any sediment that comes out....but sometimes the only way to eliminate it completely, is to renew...would only need one of those bars to block to cause the kind of symptom you are experiencing.

can be a real headache to find a blockage but needs to be done.

as an educated guess....you mention that when needle hits the red, fan kicks straight in and drops the temp....

cant remember where fan switch is on this engine, but i would look very closely around that area, as it suggests to be that either the switch itself is faulty as it didnt kick in before the temp hit the red, or the flow problem around that area is preventing the fan to switch...as the water flows through the rad before it reaches the switch...rad is a big suspect.

water pump is seperate from cam belt, auxillery belt just needs a visual check to decide if it needs renewal.

sorry about the long read, just trying to give as much helpful info as poss in one post...let us know how it goes

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just wanted to start of by thanking you for all your help so far no matter if its a short or long post!

the ford dealer was a waste of my hard earned cash but such is life lol

i doubt its an air lock as i have removed the cap twice now & let the car idle while revving & also allowed the water to flow out under pressure

not sure if a power loss problem but ford did not mention anything & i did have the catalytic converter replaced

is a sniffer test the same as a pressure test?

although ford did say the fan switch was ok i am tempted to replace it before i go ahead with any major work & will definitely keep you updated

also all the coolant hoses where previously checked by my local garage & given the all clear

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you said cat has been replaced...was it because it was either blocked or collapsed....if so that can lead to a blockage further down the system...

an exhaust blockage is capable of overheating the engine due to back pressure, have even seen instances when the manifold starts to glow when viewed in the dark....if exhaust is blocked/blocking, the back pressure would show up as a loss of power similar to towing a truck up a hill, just gets slower and slower, can eventually just die, then if left for a period of time, off you go again.

an air lock cannot be eliminated by what you have said...if there is a blockage in the flow, then stands to reason that other side of that blockage will be air/cooler water.....it could be that cooler water is then pushed around the system by the pressure this blockage will create, if it settles by the fan switch then that would explain why the fan switch doesnt cut in till the temp is in the red,

so would run it up to temp and check where the temp guage is when that fan cuts in, if its roughly just above the mid point then it must be air/cooler water that prevents it cutting in at the same point when driven at speed.

what i mean by power loss, is when car is travelling at speed, does it feel like it still responsive throughout or feel like your being dragged back more and more as temp rises.

a pressure test is using a pump to pressurise the cooling system up to a certain pressure [normally stamped on the cap] this replicates the cooling system that is up to temp...you can then check for any water leaks that only appear at full pressure, or loss of pressure in the system that cannot be seen {such as a head gasket fault]

a sniffer test is specific test for checking head gasket...either by using a recepticle with a special fluid that you attatch to the expansion tank, or an emission tester capable of registering HC [a combustion gas] which again is fed into the expansion tank...

you run the engine and gradually increase the revs... if the fluid detects combustion gasses it changes colour, if the HC tester detects gasses it registers a reading...

only place combustion gasses can get into the cooling system is via a faulty head gasket...both those tests will register even the tiniest problem.

dont dismiss the coolant hoses either unless they have all been physicly removed and visually checked...i'll put money they have only been tested by feel....pay particular attention to the smaller bore hoses because they are more prone to blockages...its quite possible that hose will be hot throughout as the water pressure can force hot water either side of blockage...thats why they need physicly checking along with their connectors, as thats the only way of knowing if water is capable of flowing through it

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yes the chalk inside the cat was broken & resulted in a rattling exhaust but this has been replaced over a week ago now......

if it is an air lock what is the correct method to eliminate this?

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Just to pitch in -

You have a 2004 Focus - is it a mk1 or a mk2?

It could be something simple - like fins missing off the waterpump, impeller sheared etc

If you are going to remove/ pay someone to remove the waterpump to check it, you might as well replace it with a new one, you can get pattern ones from about £25, often modern Ford waterpumps have plastic impellers, and the pattern ones are sometimes metal, if you take the waterpump off, best to fit a new drive belt while you are at it

Changing the waterpump may be a good place to start

If you are really tight for money, run it how it is (at least as a temporary measure)- got aircon? don't use it, it sucks heat out of the cabin and dumps it right in front of the radiator, raising the temp of the air entering the rariator. when the car overheats, put the heater on, you can turn the fan up, and open all the top vents, if its hot weather just open all your windows, (the cabin heater then acts as an extra radiator, to help cool the engine) ok, its not the most comfortable thing on a hot day, but better than the alternative of roasting/ knacking your engine or not making it home/ to work on time etc etc (or actually spending money :) )

If the coolant has been changed it must be the same type (organic or non-organic) if the two are mixed (or the wrong type used for topping up) it can cause problems - you can tell from the colour of the coolant

the fan switch is unlikely to be the source of your problems, the fan will only come on in certain circumstances, like in traffic. If the car is moving (eg, over 40mph) the fan is unnesseary Racing cars often don't have fans, ive removed my fan

The system does not need to be pressurized, this is just to raise the boiling point above 100 degrees c, because water has a higher boiling point under pressure, the pressurisation actually puts more stress on the system (gaskets/ seals etc) i depressurised mine (to protect the seals on the expensive electric waterpump) and use traditional non - organic anti-freeze (higher boiling point, lower freezing point and better conductivity) i dont recommend this for you, but its to show pressurization (or not) is uniikely to be your problem

the temp sensor is often on the head on modern cars/ Fords, it may be worth fitting a water temp gauge

You may be able to fit a thermostat that opens at a lower temprature, or have the electric fan coming on at a lower temp (it may be set at 95 degrees) this may require a special controller

finally, you could fit a manual (over-ride) switch to your radiator fan - i know some of these suggestions may seem a bit extreme, but a switch would cost under a fiver, and fixing it properly could cost 100s, these could be temporary measures untill you can afford to fix it properly, or winter comes :)

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going back the way is the heater getting hot when you try it if its not then it may well be the heater valve thats faulty sticking shut preventing the coolant flowing properly also the bottom rad hose can collapse under high speed if the hose feels really soft then this will collapse and block the flow there is an issue known to affect Fiestas, Pumas and Transits where the
heater control works perfectly, but the valve imposes a restriction on
coolant flow when the heater is set to cold. The engine then overheats
unless you turn the heater to its hottest setting.

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the break up of the cat can cause lumps of the honeycomb to travel further down the exhaust system, which in turn can restrict the exhaust gas flow...so this still could be in list of possible causes of your problem....

you stated earlier that heater gets hot and remains hot throughout, if problem was just an air lock, the air would normally settle in the heater matrix and cause the heater to blow cooler air...if you followed the test i suggested earlier in thread for heater and air remained hot, i very much doubt problem is just air.

you need to bear in mind that the hotter the engine gets, the higher the risk of blowing the head gasket will be...a cheap fix could well be to fit a manual switch for the fan untill you have funds to get the problem fixed.

as said, most likely cause of fault from info you have provided is a blockage, the water pump or a very minor head gasket fault...your best solution if your not confident to carry any of the work out yourself, is ask around for a good independent mechanic/garage...make a note of all the work that has been done including work that was carried out before the overheating [such as the cat collapse..it could be relevant] and pass that info on along with the symptoms you have now...

to be honest, as it stands, the only way forward is for someone, recommended to you, to get their hands dirty and test it thoroughly...if money is an issue, ask for regular updates as work progresses with instructions that no work be carried out without your go ahead.

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