Overcooling

[mattjk]

Thermostat most likely cause...?

Funny because if I'm sitting in traffic it will rise up the fan will kick in but then when I move off the needle hits the deck again.

I will get the thermostat out at the weekend and have a look anyway but any general ideas appreciated.

 

[bmh.01]

The temp senders fail and cause the gauge to go all over the shop, although it'll make the car run rougher due to the ecu thinking it needs to run the cold start map.

Does the top rad hose get hot as it should?

 

[sideways danny]

air in the system and low coolant level, duff sensor or a broken connection would be my first checks then the stat after that

 

[mattjk]

Cheers for the replies fellas, Yeah the top rad hose does get hot (almost too hot to touch). infact the coolant does get hot but not so hot that you cant put your hand in the expansion tank.

The gauge will get to normal if sat still but once you start moving it will always return to the bottom. The coolant is really rusty so maybe thats having an adverse effect although i have already flushed it once but its still rusty as fook

Ill flush it out at the weekend again and have another look this is on the fiesta btw not the clio

 

[bmh.01]

Simple way to prove the thermostat (although I don't know at what point they open on a festa) is to take it out and put it in boiling water to see how it reacts. Should obviously be closed when cold and open as X degrees c.

 

[mattjk]

Yeah I'm gunna do that I think, I'm fairly sure its not electrical (as it rises when stopped) the only thing is, is that the alternator needs to come off to get to it so shall I buy a new one before I do the job so I don't have to go through all the hassle of removing alternator again... I mean is chucking it boiling water got the possibility of "freeing" it up or is it just to test it so to speak?

Ps one of my mates mentioned that they can just be removed in the older cars not to sure if thats possible in modern vehicles though.

 

[bmh.01]

The boiling water is just a test if its fecked it'll just tell you, for the cost its probably worth just changing. You could probably get away with it in the summer but it'll take a lot longer to warm up, in the winter it'll be a pig. Best to just change the thermostat.

 

[mattjk]

Thanks for your help as always matey.