2002 Fiesta overheating

[sarfi]

Hello all,

I have a 2002 1.3 Fiesta Mk6. A few months ago I noticed the radiator fan was coming on frequently when sat in traffic or even at the lights. However, the temperature gauge always remained in the middle of the dial.

Then one day I got steam coming from under the bonnet and the temperature gauge (digital) went up to the nearly the black bit at the top. So I stopped the car and let it cool down. The next day I took it to a garage and they found the hose from the water tank to the engine had a small hole in it, so they replaced it.

But it didnt cure the problem of the car getting hot. My commute is generally about half hour with little traffic. When I get to the lights, the radiator fan comes on and if I leave the engine running the temperature gauge goes to just under the black bit at the top, which prior to the hose problem never happened. I also noticed my heater when on hot is also not very hot. If I'm driving it's warmish, but when I stop it's virtually cold.

As the car is quite old I thought I would have a go at trying to fix it myself :)

So here is what I've done:

Drained all the old coolant and put in new coolant.

Taken off both radiator pipes and flushed through the radiator both ways, twice.

Taken off both pipes to the heater and flushed that through.

Put in some radiator cleaner and flushed it all again afterwards.

Hopefully got rid of air by leaving the water tank cap off for a while.

 

After this, the car can be run at idle for a little longer before the fan comes on, but there is still warmish air through the heater and the fan coming on so quickly is not normal for my car.

I've noticed that the top hose to the radiator is very hot, but feeling the radiator itself, it's only hot on the top half. The bottom half of the radiator is cold and the bottom pipe from it is cold. But, both these pipes become difficult to squash when the car is up to temperature.

Both pipes leading from the thermostat housing to the heater are hot, but the heater still blows warm.

 

What could be the issue do you think? I have bought a new thermostat and will have a go at fitting it this weekend. But because the top hose is very hot, surely this means the thermostat is opening to let the water into the radiator and thus working ok? Can it be that it's not opening much and there's not enough flow to push the hot water all the way around the radiator?

(I've attached a picture of my thermostat housing - it's on the top right of the engine.)

Many thanks, Sar

 

[isetta]

I don’t know for sure exactly how modern thermostat work, but they might still be like in the old days. A     Spring holds the thermostat closed to stop flow, in middle of thermostat is a capsule of wax . The wax heats up, expands and pushes the thermostat open against the spring. So when a thermostat fails partially or completely it restricts flow and causes overheating. Eg when wax leaks out of capsule.

[sarfi]

24 minutes ago, isetta said:

I don’t know for sure exactly how modern thermostat work, but they might still be like in the old days. A     Spring holds the thermostat closed to stop flow, in middle of thermostat is a capsule of wax . The wax heats up, expands and pushes the thermostat open against the spring. So when a thermostat fails partially or completely it restricts flow and causes overheating. Eg when wax leaks out of capsule.

This is a picture of the thermostat I bought. I actually bought two as I wasn't sure which was the right one :) I don't know if it has any wax in, but would restricted flow from this be responsible for the radiator only being warm at the top? Thankyou.

[Sharky51117]

Probably you must change radiator! 

[Paulkp]

Water Pump ?

I don't know how to check flow on a tranverse engines where there is not a radioator cap to take off........

On an Old Ford, you could alays see coolant flow.  Whilst revving the engine, the cap could be removed with care, and you could easily see the flow.  Hot out of the engine at the top of the radiator, and cold back in at the bottom

[Paulkp]

As an aside - water pump on my 1.6 petrol Fiesta was changed when the cambelt was done.

[isetta]

does look like the wax type. wax in the centre brass part.

when you take old one out, test it, or even testing new one before installing, put in a saucepan of water on the cooker, heat water and the thermostat should open before it gets to boiling point. the ones I have seen had the opening temperature stamped on the metal. don't know if they all do.

this one does look a bit different to old ones I remember as this one seems to have an extra bit on the bottom.

this explains some stuff although last bit on how to check is not relevant to modern cars due to position of collant cap.

https://www.carbibles.com/car-thermostat/

 

[Paulkp]

I don't know this engine, but does the unopen thermostat inhibit flow to the heater ?

I would have thought that there would always be flow through the heater, not just to warm up the driver, but to ensure the water pump is not trying to push the coolant up a dead end ?

[nicam49]

The heater not pumping out any heat makes me pretty certain that it's your water pump. Sometimes the impellers in them slip on the shaft, 

[sarfi]

Thanks all to those who have offered advice and shared their knowledge :)

The waterpump has indeed failed. I noticed a spray of coolant on the underside of the bonnet (which hasn't been there since the car has begun to overheat) and looking under the car reveals a steady drip from the pump spindle.

I will change the thermostat and thermostat housing whilst the coolant is out so hopefully that should cover everything.

23 hours ago, Paulkp said:

I don't know this engine, but does the unopen thermostat inhibit flow to the heater ?

Yes, the thermostat is sitting between the two heater pipes. I got really confused about what was going on in the housing, but I found these two brilliant diagrams which explain it really well:

Would the radiator being only hot in the top half be down to trapped air because of the water pump failure, or possibly reduced flow because of pump failure and/or failed thermostat?

Or, could a blockage in the engine be responsible for reduced flow/increased pressure on the water pump causing it's failure?

I've been advised if there really was a coolant block in the engine, it would be overheating very quickly indeed and that seems a plausible reassurance.

Thankyou once again!

 

 

[Paulkp]

I think the failure of the water pump would be age related, as Nicam said "Sometimes the impellers in them slip on the shaft" and yours is 17 years old. On RWD Escorts and Capris, you would be lucky to get 10 years !

Radiator being only hot at the top would almost certainly be down to lack of flow from the water pump.

Where did you get those diagrams ?  They are what used to be in Haynes manuals, when they had technical illustrators !

I have just changed my 12 year old expansion tank on the Fiesta - visible bulges, with what looked like stress lines, easy job, once headlight out of the way.

Keep the shiny side up !

Edited December 12, 2019 by Paulkp