K series 111s running at 2 different engine temps

[zebedee]

normally runs at 84, but since some work was done on it now runs at 84 and sometimes 90.

My theory is this: Start from cold, running at speed so good airflow through rad, temp stays around 84, all fine.

Stop in traffic or petrol station - bit of heatsoak and temp rises to around 91 where the fan kicks in. Fan kicking in causes electrical load which leads to a false display of high temp (on basis on many (all?) cars, using fans, lights etc adds 'false' degrees to the temperature display.

If the fan is adding 6 degrees of 'false' temp, then although it is back to 84 in real terms, the car is displaying 90 and presumably thinks it is running at 90, so doesn't switch the fan off.

Does this sound likely and is the best solution to increase the temp the fan should come on at to say 95? Is that even possible and if so how do you do it?

[400SE Dave]

Could be the stack temp sensor on it's way out, the Blue one. Mne gave some odd readings before it gave up completely

[thegreenhell]

What work did you have done? If it was anything that involved draining the cooling system at all could it be that it just wasn't bled completely when it was put back together so there's a small air lock in there giving false readings?

[mattshiz]

I didn't think the fan came on til it was above 100 degrees.

Could be an airlock in the cooling system somewhere. Has the coolant been replaced recently?

[kambites]

Mine generally hovers around 87-89 when moving at a decent speed rising to something like 100-105 before the fans cut in around town. If the fans are kicking it when it's reading 91 on the temperature gauge, one of your senders is probably knackered.

[zebedee]

The coolant was totally renewed as it had a rebuilt head put on it. So what would the airlock be doing to make it run at 2 different temps? Yesterday it did at least drop from 91 back to 84 once up to speed again so maybe it is an airlock that is sorting itself out?