its normal for the temp to drop with blowers on - dunno about the revs though

 

should be the thermostat. mine was doing the same. i replaced the thermostat with a new one and the problem disappeared...

if you decide to replace the thermostat, go with ford made. aftermarket thermostats may differ in temperature settings.

 

well, actually i think different. yes, the temperature of the coolant fluctuates as you drive the car, put the heater or aircon on and off, travel at constant speed or got stucked in a damned traffic jam etc, but it is not something that the temp gauge moves between 1/4 and 1/2 positions or it travels along the path indicated "normal" on the gauge. the logic behind the cooling system is to keep the engine temperature as close to the ideal calculated temperature as possible and keep it constant while doing this. so, if you have a healthy cooling system with suitable coolant in it, you should have your temp gauge pinned at exactly the same location, no matter what AND your engine should reach the regular operation temperature in the shortest time (mine is around 4-5 mins or ~5 kilometers driving).if your temp gauge likes travelling through the white zone (normal range), this is not normal, even the engine temperature is within acceptable limits. you should have your cooling system checked, starting from the thermostat and the coolant quality.

 

Thanks for the replies. I've just 'phoned a local Ford dealer, they tell me that I can't buy the thermostat separately, I have to buy the housing as well, for a total of £55.75. that's supply only :angryfire: :angryfire:

 

the ford price is :BEEP: , and yes, it's normal for the temp gauge to drop with heater on full, as the heater coolant bypasses the t-stat, and will always circulate thru the heater core no matter hwat. Engine Temp will fluctuate during changing driving conditions, and the gauge will reflect this. WHen car is stopped, i.e. during stop and go, the fans will come on when temp gauge goes ebtween the m and a in normal, the t-stat wil be full y open at this point, but there is no air going thru the radiator to cool the coolant, and so it will heta up, till the fans come on. During driving conditions, the ram air going thru the radiator will cool the water in teh radiator, and the t-stat will cycle to keep engine temp at a constant. But the heater core water will always cirulate even if the t-stat is shut tight. Hence, in cold weather, with a cold air being fed thru at 4 on the blower motor, will cool the engine more than it can produce ehat, and will cause it to cool. There is no problem with your cooling system if it does this. Even if the temp gauge fluctuates thru the normal range, during chaning driving conditions, it will move the needle, your needle will not stay pegged in the same place, no matter what. in cooler outside temps, the needle will be slightly lower, in traffic it will sit higher, it's normal, and nothing to worry about. If it sist in the n or below at all times, yes, thats a problem, also sitting above the a hten thats a problem, but other than that, no, you are fine.

 

my thermostat was sticking open and it would not get up to temperture, unless i was sitting still in traffic. if your car is getting up to temperture in about 4 to 5 mins and does not overheat there is nothing to worry about :L

 

my thermostat was sticking open and it would not get up to temperture, unless i was sitting still in traffic. if your car is getting up to temperture in about 4 to 5 mins and does not overheat there is nothing to worry about :L

I think that part of the "problem" might be the high flow rate of the Duratec waterpump, so if the thermostat is slow to close when the heater blower is turned on full, the high volume of coolant flowed causes the temp gauge to drop. Perhaps the question should be: if the gauge drops by a 1/4, how many degrees is that? If it's 5'C then its probably OK, if it's 20'C then that's not good, thermal cycling of the head leading to head gasket failure and a cracked head etc.

The local Ford dealer told me this morning that:

1) The gauge shouldn't drop when the blower is on full.

2) They've never heard of this "problem" with Duratecs. If it is a problem.

At the moment I can manage the "problem" by only using the blower on full for a couple minutes, but that's just a temporary workaround. I think that the thermostat might be sticking slightly when it should be closing following operation of the blower on full, so perhaps an additive might help? Or run it for a few thousand miles and see if the "problem" goes away, yes that sounds like my sort of solution :whistling:

Huh, never had this problem with the Zetec engine.

 

You dont have a problem

The cabin heater is taking heat from the engine - so naturaly it will cool your engine down. If your temp is in the normal range - then dont worry.

By the way - Ford talk turd if you havent noticed (£55 quid!) - you must be able to get a new thermostat on its own, cars are just designed that way - its a consumable part.

I dont think you have a problem at all, but change your thermo if your worried (dont be suprised if it does the same though.........)

 

You dont have a problem

The cabin heater is taking heat from the engine - so naturaly it will cool your engine down. If your temp is in the normal range - then dont worry.

By the way - Ford talk turd if you havent noticed (£55 quid!) - you must be able to get a new thermostat on its own, cars are just designed that way - its a consumable part.

I dont think you have a problem at all, but change your thermo if your worried (dont be suprised if it does the same though.........)

The gauge stays in the normal zone, but it drops from just below 1/2 to just above 1/4. It looks like a big drop but then I don't know how many degrees the temp drops by. I've got a couple of temp transducers that I can strap onto the coolant hoses, not as accurate as measuring the coolant temp but no risk of leaks. The readings won't show absolute figures but will show trends.

I've driven a few cars where the temp gauge drops by a needle's width in cold weather, but not by nearly 1/4 of the gauge range. I was hoping that a few owners would tell me that's normal for a Duratec, I'm still not certain. I don't think it's a serious problem at the moment because I can run the heater blower on position 2 with no movement of the needle. A quick search on the internet reveals that TDCi owners run cars that don't move the temp needle for several/many miles, but it does seem to vary from car to car eg:

http://www.honestjohn.co.uk/forum/post/index.htm?f=4&t=20405

includes the comment:

"> The Ford Main dealer has had the car for 48hrs and agrees with my diagnosis. They have reported it to Ford who advised them they have received a great many complaints about this. However, it would appear they do not have a fix for it and are unlikely to. The fault [they call it an indication] is not safety related. Apparently they consider that if the car gets hot eventually and the temperature gauge reads somewhere between 1/4 and 3/4 scale then that is OK.<"

£55 was a surprise!

 

I just got a proper Ford Jobbie at Ford Alperton with the O Ring for £11 ,93degrees stat . There talking bobbins if they said £55.

 

Hi Hellboy,

Is the thermostat for a 1.8 or 2.0 Duratec petrol engine (Mk3 Mondeo)? Is the thermostat electrically operated?

I've read that there is a Focus equivalent that fits the housing, and it's purely mechanical with no electrical operation.

What were the symptoms that lead you to replace the thermostat?

I've not gone any further with the problem yet, I find it difficult to believe that the thermostat has failed after 40 000 miles, but the car did stand for a while at the (non-Ford) dealers before I bought it, so maybe it's sticking. I should take it back to them but I want to make sure I know what the problem is, if I can get a new thermostat for £11 and it fixes the problem then that's less than the petrol cost for me to take it back to the dealer.

 

I've had my thermostat replaced this morning, car is a '51 2.0 Duratec HE engined Zetec. Anyway, Thermostat Assy £29.11, 3 ltrs anti freeze £11.76 + 1 hours labour and VAT = £100.89. All done at the local dealers.

 

It'll be interesting to know what your temp gauge does now! Did the dealer say that the thermostat was definitely U/S? Has it got an electrical connection?

No problems with temp gauge in slightly warmer weather, some warm air from the vents after about a mile.
Worked on a site today and watched someone put cardboard in front of the radiator of a 53 reg Ford van (Connect?) fitted with an Endura diesel engine, the driver told me that the heater never gets warm in winter without blanking the radiator. It must be catching.

 

Temp gauge goes to Normal then doesn't move an inch whether the heater is on high or low. On high its too hot inside the car now, no, I'm never :BEEP: satisfied.