Hi matt If the thermostat was partially stuck open the flow would be all the time, thus keeping the flow going through the radiator and the fans would come on even less.

is it the rad fan or the engine bay fan coming on as the front fans are hard to hear from inside the car
If it is the bay fan then you may suspect the fan switch sticking.

As long as the coolant level remains at the correct level then not to many worries until you sort it out.
BTW you may want to bear in mind that a temp guage at the middle does not neccesarily tell you the engine temp is ok.
A sensor with no water around it can also read low as its the water that conducts the heat to the sensor. so, in short no water means it can't read the temp and will temd to read low.

A failing water pump may cause your symptoms though.

 

coolant leve is fine, its definately the rad fan,its on when i get out to check when i get home,i thought water pump but i hope not, what if the thermostat is only opening half way due to crud or such like but it can still shut, i have found a temp probe that i use to use at work to check wellding plates, im going to use it to see what temp the water is in various hoses, you just touch it on it and i get a reading, hopefully i can see if indeed the water outlet hose from the engine is at 102c, ill see what the xpansion is at when the fan comes on

 

a quick update
started car removed xpansion bottle cap and saw water circulating so i assume jiggle valve is ok.
car was running for at least 10 mins bfeor pipe to radiator got warm, so i assume thermostat is good.
measured temp at radiator core after 30 mins and that was 86c so that appears ok
car run on idle for 35 mins with no cooling fan cutting so i assume it and the stat on the ecu are ok
water circulating ok temps on return are good so hopefully water pump is good
ill keep an eye on it
temp gauge didnt move at all......absolutely useless.
maybe its just one of those strange quirks of the car.

 

I had this on my first F, the temperature sensor on the top engine was faulty, tricking the ECU into thinking that the fan needed to run all the time. It took about half an hour and £12 to fix, the fan then cut in and out as it should AND my fuel economy was miles better too because the ECU did not muck about with the mixture.

Nick.

 

to change the fan/temp gauge semsor do you have to drain the coolant?

 

Hi there

my car is the same age as yours & I had the same issue of the fan coming on after 5 mins or so on short journeys & when I was stationary to open the garage door.

As part of on going maintainance I replaced the radiator, not due to a leak but because it looked rotten and 50% of the fins were missing & just the cores remained.

With the new radiator fitted the fan rarely comes on.

Mite b worth peering through the grill & inspecting the state of your rad?

 

the rad appears in good order, i had a nice temp drop across it yesterday its not got any signs of damage, when i got home today the fan was on so i checked all the hoses with my temperature meter and they showed 62c the rad was at 13c, obviously where cold air had been blowing across it. so i switched the igntion off and the fan stopped, i restarted the car and run it for another 10 mins and the fan never came back on, so if the car was overheating( which the hoses suggest it wasnt) why did the fan not restart, my money is on the fan sensor. im changing the coolant soon so i will change the sensor and mechanical thermostat as routine maintenance.
boy are old cars a pain, if it aint one thing its another

 

^ agree.

If the temperature guage reads high it indicates a problem elsewhere. If it reads normal then it indicates no problem. My temp hovered around normal most of the time. Would read higher after prolonged high speed driving in hot conditions - Route Napolean could always get the reading up.

After 9 years I've seldom had the cooling fan cut in. The engine bay fan was a frequent visitor. My latest TF (2009 NAC 1235) now switches engine bay fan on much earlier than before - sounds a good idea to me.

 

matt you worry to much, do not forget the water temp sensor is near the engine block, the water has to travel a long way to the radiator, our rad never feels hot but the fan still comes on, if you are checking the water temp on the outside of the hose the water inside will be miles warmer, also our temp guage hovers around the half way point.

 

your not the first person to say i worry too much......it drives the missus mad. i havent had the car that long, im still getting used to her little quirks,she's nothing like all the others( sounds like im describing a girlfriend....lol)
im changing the coolant next week, as part of some routine maintenance ive chucked a new coolant sensor and thermostaic valve her way, it wont hurt to change them and saves a 2nd drain to the system later.i just hope i can do it, all them bleed valves might be a problem single handed, i might get the missus to get her hands dirty.

 

I wouldn't go near the thermostat unless you are very well equipped, patient, certain it is defective and you have no way of avoiding it. Your symptoms don't sound as if it is faulty and it is a b****r to do.
The brown sensor could be a good bet.

 

ive worked on all sorts of machines in my time as an electrical engineer, ive got loads of time as its not my daily drive, so ill have a nosey and see what happens. ive got my techinal manual for support. it cant be that hard, if it goes t*ts up ill blame the wife.......lol

 

all done..... wow the thermostat was a little tricky......lol. I found what might be my problem, one of the metal pipes under the car has been crushed and i think this might be restricting flow on the system. Its created a right old problem getting the hose to seal back to it as its right where they join. still monitoring it for leaks and problems, im asking santa for a coolant alarm.

 

Glad you got her all sorted, Bit of a pain, but now you understand her cooling system better, a lot of the worries will go away.