Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - Flexo81

Hi guys,

I have strange problem with my temp gauge.

If I drive around town, the engine warms up as normal and the temp gauge will sit exactly half way as it has done since always. As soon as I stick it in 5th and continue forward along a quicker road, speeding up gradually, the temp gauge will suddenly shoot off into the red. It wont flip up in half a sec or anything, its gradual but quick, like 5-10 seconds and will either hover above the three quarter mark or just keep going till the very end.

When I slow down, into 4th gear traffic or less, the gauge will drop, back down to the halfway mark, maybe hovering around just above. Then again if I speed up through the higher gears it will rise again.

If I stop and shut the engine off for literally 2 mins, then turn it on, the gauge will sit at exactly half way again.

The strange thing is, I can sit in neutral, hold revs at 2500 for a while (faster than what they were in 5th) and the gauge will remain static at the half way point. To me this confirms its nothing to do with the head gasket.

Other snippets of info:

- No hot air available through internal heaters/blowers or air con - this started at same time as temp gauge thing earlier this week.

- I have noticed in the past couple weeks or so, the radiator fan kicks in after I shut the car off - regardless if the temp gauge is in the red or half way. Simpyl assumed its because of the hot weather recently.

- Have had an oil change as (I thought) the oil was a little low on the dip stick; garage said it was only a litre off full.

- Have had the thermostat replaced yesterday, coolant bled through - all pipes seem warm where they should be, suggesting coolant flow and working thermostat with no airlocks.

- There are no leaks (oil or coolant), coolant levels remain high.

- Coolant is not contaminated

- There is no white smoke coming from exhaust

- ECU Diagnostics confirmed that the temperature was apparently what the temp gauge was reading when it was overheating, so cant be dodgy electrical sensor.

- Cant really be the heater matrix as although it would cause only cold air, it wouldn't cause the overheating (I believe the matrix part of the cooling system junctions off from the main cooling system; so even if it was blocked, it wouldn't cause the coolant to stop flowing)

- There are no strange noises comuign from anywhere in the engine bay.

The next thing to replace is the radiator or the water pump. I don't know which one to go for and both are about £170 fitted; and even then, theres no garuntee it will fix the problem.

My gut feeling is water pump, because although flowing the coolant, it is not flowing it hard enough - possibly not hard enough to reach the heater matrix, but, why is this problem only apparent at speed?

Could it therefore be the radiator because not enough air is being sucked in at speed - but in that case, why doesnt it overheat when I'm at a standstill and holding the revs high and why does it cool down quickly when the car goes slower??!

Very interested in your opinions and reasons for them...

Thanks!

Matt.

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - Cyd

Sounds to me like you may have a blockage in your heater matrix. this may cause overheating in a modern car, because where cars used to have a water valve to control heat, now most have full flow through the matrix at all times and the heat output is controlled by flaps which mix warmed and cold air.

Give the coolant system a good flush out with a high pressure hose.

Has there been any signs of corrosion in the coolant at any time, now or in the past? As you say, it could be the water pump. Don't know these intimately, but in general corrosion particles can errode the vanes on plastic impellors and zinc impellors can both corrode and errode. It's also possible the pump shaft has snapped - at low load the air flow over the block may be enough to keep the temp down.

Is the expansion bottle a single or multi pipe job? If multi, then usually one can discern flow through the reservoir. Take the cap off and see if coolant is flowing, that'll at least tell you if the pump is pumping. Or run it up from cold and when the stat opens feel the hose to the rad at the rad end to see if there's a rush of hot water.

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - jc2

Pump - damaged rotor.

Edited by jc2 on 28/07/2013 at 19:28

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - madf

Blocked radiator and heater matrix.

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - bathtub tom

Modern cars don't have analogue gauges, only digital ones. That means your temperature gauge probably only reads cold-normal-hot.

When did you last renew your coolant, within the manufacturers time-scales?

I'd suggest a good flush and new coolant would be the cheapest starting point.

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - Collos25

Radiator fan not working is a common fault that or the water pump has stopped working.

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - Ski111

Did you get this resolved? What was the problem, as I have exactly the same issues and have alread change the stats to no avail.

Thanks

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - jimmythekid

I have also got this problem, did anyone manage to fix theirs?

Cheers

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - dogdays

Either a sticking thermostat or slipping pump rotor. First test temperature of water exiting from thermostat when overheated with laser thermometer before considering the pump. Aircon will usualy cease working in engine overheat situation.

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - Last Hope

If the temp gauge is rising so fast, it leads one to wonder if this is a real reading ? A hand held remote temperature guage should prove that the head temp is right or wrong and the radiator too. Having proved that the engine is running at the correct temp, one can look to the wiring circuit of the guage etc. With some cars, pulling the temp sensor wire off the engine, will send the dash guage very quickly to the red. If this indeed happens with Fiesta circuits, then it is to these connections one should look, and not spend a penny in pumps, rads or stats.

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - JonFinn

Hi

I'm struggling with the exact sam thing. Did you eventually locate the cause of this problem ?

Cheers

Jon

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - JonFinn

Hi

I am currently experiencing the exact same thing. Did you or anyone else here ever find out what caused this ?

Regards

Jon

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - Jonzak

SOLVED

Just to let everybody know, I experienced the same issue:

Water pump, damaged rotor

Parts+ labour 150€

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - Paul Ralph

Hi guys have a ford mondeo titanium 1.8 tdci a few months ago the wet belt snapped and coursed loads of damage to engine defor wet belt snapped have a problem with the car overheating and lossing Walter from expansion tank have since done the work myself on the car changed head gasket, walter pump, thermostat thinking this would solve the problem have only just got car back on the road and yet am still losing walter from the expansion tank can anyone help in diagnosis of the problem.

many thanks paul

Ford Mondeo Mk3 - Tdci - Strange overheating problem, only at speed - madf

Head skimmed? Inf not, probably warped from overheating.

 

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