Eratic Temp Gauge Readings Ford Focus

The correct way to refill the coolant on the 1.4 & 1.6 engines is to remove the heater supply hose at the rear of the engine (below the coil), then use a funnel to fill the cooling system via that hose until it comes out of the engine.

If you don't follow that procedure, air locks are likely, as you have discovered.

Sometimes it will rectify itself quickly, in which case the coolant level will suddenly drop so the header tank is empty; topping it up will restore correct function. If it doesn't do that within the first few minutes of refilling, you should not continue to drive the vehicle.

In your case, I would suggest you need to buy some more anti-freeze, drain it, then refill it in the correct way.

Chris

or leave it running with the filler cap off or very loose until it has reached full temperature, having the cap loose will allow any air locks to more easily come up and into the tank, you will easily spot when this happens.

Hi Chris I drained system again and filled as per your recomendations and the care has made 2 x 50 mile journeys so far without a problem. So thanks for the advice.

I did look on you tube and found several posts on how to do it and all of them were just re filling the system via the expansion resevior!!!!! That certainly would not have worked on mine!

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Thanks for letting the group know.

Glad you got it sorted.

Chris

Hi Chris Unfortunately when the car was taken on a longer journey of approx

100miles the temp gauge twice went into the hot zone for a short period and then drops back to normal. The overheat warning light on the dash board did not illuminate.

To be honest I was not convinced it was an air lock in the first place but you have to work your way through solutions in a logical manner.

I think I am left with it being either a faulty cylinder head temp sensor, a faulty radiator fan temp sensor of is it possible that there could be a very small gas leak through the head gasket. I notice the expansion tank cap has a spring loaded safety valve so I am guessing it would prevent any obvious ove rpressuring of the system by a gas leak through the head gasket.

get a sniff test done by a garage or buy a kit yourself (it is called a block test kit) to establish whether you have a head gasket leak.

In message , MrCheerful writes

Is it certain that there actually IS any overheating? Some of the Mk1 Focuses had a problem with corrosion of the speedometer cluster printed circuit board.

With my 04 reg (at 9 years old, 45k miles), after being intermittent a couple of times, most of the cluster functions totally packed up (IIRC, no temperature gauge, no speedo, no rev counter and no odometer). As a Ford replacement would have been at least £450, I did a bit of Googling for advice, and found that corrosion could be the problem. Fortunately, I managed an easy fix (although I have had my fingers crossed for the past three years).

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From your OP, it would seem that the temperature was behaving normally until the coolant was changed. It then completed a number of lengthy trips during which it over-heated several times, sometimes lighting the MIL. After re- filling correctly, it now goes into the red on longer journeys, but without the MIL illuminating.

If the above is an accurate summary of events, I would suspect that the original problem was indeed an airlock, and the over-heating caused by continuing to drive it under those circumstances has blown the head gasket.

Chris

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It would be unlikely that a faulty cluster would *only* show high temps, with occasional MIL illumination, and a very unlikely coincidence if that happened immediately after a coolant change carried out in a non-standard way.

Chris

At one stage, Fords were selling the complete cluster as a 'good will' gesture for about a hundred quid.

I remember that there could be a problem on a focus with the cylinder head temperature sensor wiring 'picking up' from the spark plug leads. The sensor is mounted between the centre two spark plugs and its wiring can touch the spark plug leads. The fix was to use plastic tie wraps to hold the temperature sensor wiring away from the spark plug wiring.

Interesting!

With mine, it was obvious that some of the soldered joints on the rear (exposed) side of printed circuit board were corroded. There were probably others on the other (front) side, which you can't see.

To get to the front side would have meant pulling the pointers off the dials, so I decided first to try just cleaning the rear side with a toothbrush, and then giving it a light misting with WD40 (taking care to prevent any spray reaching the front where the dials were). To my relief, this seemed to be sufficient, and so far 'the fix' has lasted three years.

Anyway, I gather that this isn't OP's problem!

It is most unlikely that surface cleaning and applying fish oil will cure a dry joint.

More likely just a build up of oxide at the loom connector plug that was displaced by unplugging and plugging back in.

Maybe - but on the other hand, it could have been the corrosion bridging the printed circuit tracks (of which there were certainly signs). If the connector was a common problem, why would Fords have been selling the complete cluster as a 'good will' gesture for about a hundred quid?