My mondeo (59 plate 1.8 tdci) has been overheating recently. Had it in the garage a month ago and was told that the heater matrix was blocked. They cleared it and had run fine since until a week ago. Same symptoms. Overheating. No heat from AC.

 

I know for a fact it isn't the thermostat, as it was my first thought so I replaced it and both old and new were fine (opened properly when covered in boiling water) and garage has since done the same and said it was fine.

 

Garage doesn't think its the pump as they had it off a month ago and said it was pristine at the time.

 

They have had it for 3 days and can't tell me what's wrong with it yet.

 

Running the engine none of the hoses are getting hot anywhere. Either side of rad. Coming out of thermostat or either side of heater matrix.

 

However when I replaced the thermostat I did seem to get it working after following a bleed procedure I found on here about running cycles of 2500 rpm then 4000 3 times. But the second I restarted the engine it had stopped working again.

 

I can't see any coolant circulating and if I pull a radiator overflow return pipe off the expansion nothing comes out of it.

 

Don't think it's the head gasket as no oil or bubbling in coolant and no "mayo" in oil.

 

Any help is greatly appreciated.

You've got to assume it's the pump then. Sometimes the impellers slip on the shaft. How is the pump driven on your model.... if it's from the timing belt, then you can eliminate it being that.....unless someone else has any suggestions? 

 

I believe it's a belt driven pump but. Not 100%. My guess was the pump but garage have been adamant it can't be that as it was pristine last month. I'm of the opinion that means bugger all and it could have failed in the mean time due to an airlock causing it to burn out if it had no coolant circulating through it etc.

Take the thermostat out completely and run the car with out it. The engine should run almost cold and the radiator will be warm but not hot. If the system has got an air lock in it then the air will find its way to the radiator. Replace the thermostat after a couple of days, and things should be back to normal.

If your thermostat housing is of a type that must have a the thermosat fitted in order to seal then get an old one and take the middle out of it.

So the garage have today told me the head gasket is gone. I'm at a loss as they had the car "repaired" 6 weeks ago supposedly unblocking the heater matrix.

 

Can you edit your details to include what model, year and engine you've got? Gawd knows how the garage diagnoses a head gasket can cause your symptoms.....usually hg results in coolant loss.... were you getting any? Also very rare for a diesel to have hg trouble, but you've not told us any details of your engine... 

MONDEO ZETEC TDCI 125 1.8L Diesel. 59 plate.

 

Had some coolant loss on one overheat occasion (last Monday) but I'm pretty sure the coolant was boiling as not getting to rad and just increasing the pressure until the overpressure release on the expansion tank kicked in to stop it bursting. Other than that no notable coolant loss at any point Since I have had it.

I know garages can do what is called a sniff test that is usea chemical that changes colour in the presence of hydrocarbons (from the engine) in the coolant. However its not as sensitive to diesel fumes as it is to petrol. You can buy the kits on ebay for £20ish. I saw a Wheeler Dealer episode where Ant pressurised the coolant system to check for leaks.. . I think he took off the oil filler cap to listen for any air escaping, which would have indicated a hg problem. I'd want to see proof that either or both of these tests have been carried out, but it's very rare for a TDCi hg to go, but I'm more familiar with the 2 litre version. Hopefully someone else on this forum will contribute some thoughts...