AndyRB5

Thought I would try here before signing up to a Ford forum!

My daily drive is a 2006 Ford Focus 1.8TDCI, the coolant temperature drops about a quarter of the gauge span when accelerating or going uphill (basically when the engine is under load). I have searched google high and low and everything it kicks up refers to coolant temperature increasing under load and decreasing at idle/coasting where as my car is opposite?! The car takes about 20-30mins to fully warm up under normal driving conditions. Could it be a stuck thermostat?

cheshire_carper

I had an issue like that on a gtd and it was actually a faulty temp sender. It might not be cooling but the temp sensor is poopy

AndyNFRS2k

Yep, same as on my Polo tdi - dodgy sender unit.

Replaced and all is now well, loses temperature when idling/coasting, and even better mpg!

fluffyninja

I assume basic checks have been done for stuff like correct coolant levels, no signs of leakage, no signs of discolouration of the coolant from exhaust gases.
Those are potential symptoms of other problems that could cause erratic readings but in most cases I'd have thought they'd send it high.
Anyway could be useful additional information to help with diagnostics.

AndyRB5

Thanks for your replies, yes done the usual checks, it all seems fine and the car is running fine. I have just ordered an OBD2 reader to see if any fault codes have been kicked up before I start semi-blindly changing bits and pieces. Just seems odd that the temperature drops whilst under load, everything on the internet relates to increases in temperature under load

martin j

Could the water pump be failing, drive belt slipping? when under load it's circulating the water better at an increased speed and so pushing the water through the rad or even around the block?

AndyRB5

Yeah potentially I guess, although no sign of belt slippage. Water pump could be a possibility but it's only 30k miles old. I will see if this OBD2 reader kicks anything up and if not I will investigate further!

Heinz '57

Two guys on here have told you that they had the same problem and cured it by changing the temperature sender/sensor.
Why would you not do the same particularly as you asked for advice?

AndyRB5

Thanks for your input, as I have stated above I was waiting to see if the OBD2 found any fault codes before semi-blindly changing bits - good root cause analysis practice!
I received the reader yesterday and ran it for codes last night, it brought up P0490 which is 'EGR Control Circuit High', I have done a bit of reading and it doesn't look like that would effect coolant temps, so I will now look at changing things like the temp sender etc. as well as trying to sort the EGR valve.

Heinz '57

Thanks for your input, as I have stated above I was waiting to see if the OBD2 found any fault codes before semi-blindly changing bits - good root cause analysis practice!
I received the reader yesterday and ran it for codes last night, it brought up P0490 which is 'EGR Control Circuit High', I have done a bit of reading and it doesn't look like that would effect coolant temps, so I will now look at changing things like the temp sender etc. as well as trying to sort the EGR valve.
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If that was your intention why on earth come on here asking for advice which you were never going to take? Why not just go ahead with your "good root cause analysis practice"?