Overheat

[ian]

Very occasionally, my water temp gauge moves to the right a bit, indicating some degree of overheating.

The gauge generally returns to normal quite soon if I ease up a bit - have also tried the heater on full which also brings it down smartly.

No coolant loss or other obvious indicators. Oil temp remains steady.

Originally considered that sender or temp gauge might be failing, but in view of above think it is actually overheating.

My latest guess is it could be a cooling fan/fan sensor that is intermitently "sticking".

Has anybody experienced similar please?

Cheers,

ian

[andrewturner]

It sounds like the viscous fan. I had the same problem creeping in traffic, however on the road it was fine. Just went a few degrees over centre.

Do a quick search, the part is about £100 plus 15 mins to fit. It's very straight forward.

[ian]

Thanks Andrew, will get the viscous fan replaced.

Ian

[c_w]

The temp sensor is only associated with the electric auxillary fan at the front. This fan is primarily the aircon fan so 99% of the time you will only see this come on when the air con is on. It is however a "backup" fan to the viscous fan but is triggered by the temp sensor in the radiator which is set really high and needs around 3/4 or higher on the temp gauge to come on which is why ordinarily it will NEVER come on due to the viscous fan keeping the radiator temps down all the time.

My gauge fluctuates a bit sometimes showing slightly over and then slightly under. In very hot conditions and with the aircon on it actually shows just under normal all the time!

I'm not sure how much over the middle you mean so you could try changing the viscous fan but IMO you might not see any change if it's going a fraction over.

[inside]

Originally Posted by c_w

My gauge fluctuates a bit sometimes showing slightly over and then slightly under. In very hot conditions and with the aircon on it actually shows just under normal all the time!

Mine either, as you say in both directions. I was a bit worried and changed most of the things including w/pump, fan coupling, temp.sensor, thermostat, hoses... and it changed nothing.

[ian]

For the first 150K miles I have driven the car, the water temp gauge stayed steady under all conditions. Its only in the last year or so that I have had this (very) intermitent problem.

My logic is that something has stopped working as it should.

[c_w]

Mine seemed t o be the same and I don't know whether I have just become more obsessed with it and it has been like that all the time or something has changed. I renewed the thermostat and it was the same, this usually being the most likely culprit of fluctuations like this.

You've not said how far over the gauge it's going? In mine from the driver's seat it goes over by a needle width perhaps, although viewing the gauge "head-on" by moving your head to the right it is central.

[ian]

cw, needle at most moves right to (say) 3/4 at most - not enough to feel the need to stop the car. When it returns to normal, it likely won't happen again for some weeks (car used most days).

Just isn't right though!

[inside]

Mine moves less than to 3/4, I would say 2-3 needle widths in either direction. When pushing it, it stays in the center. And when I cool it down (high speed, low revs), it goes to the left. It goes to the right only in not so hot weather and when driving slowly through city. But when I push it or when the weather is hot it stays at the center.

I also don't remember doing it since ever, but since than I've replaced many things and it did not change a bit.

Altough it is obviously a cosmetic issue, if you find a solution, let us know

[c_w]

Originally Posted by ian

cw, needle at most moves right to (say) 3/4 at most - not enough to feel the need to stop the car. When it returns to normal, it likely won't happen again for some weeks (car used most days).

Just isn't right though!

Ah right, if it's getting to 3/4 then that's definitely not normal; the viscous fan eliminates this ever happening when stationary/slow speeds as it's constantly cooling the radiator in various forms of "lock". I would look at the viscous fan in that case. This is behaviour you would see with the viscous fan removed; the temp goes up pretty high and perhaps your auxillary fan is cutting in to bring temps down (but it will to show a high temp on the gauge to do this as coolant temp is in the block but the aux fan temp sensor is in the radiator) and/or it's cooling when driving.