XSeries-forum

so i was out in the m3 today (pretty warm) and i got into a traffic jam in town and the temp guage went over dead centre as all bmws are, but not passed the dot that would be around 3/4, as i left town it headed straight bavk down towards the lower dot 1/4 (there is no centre line/ dot, anyway followed a bus up a long steep hill at 10mph for a mile and up again, passed the buss at the top and all well for the rest of the journey, now ive never had a bmw go over half, and not noticed this on this car before,  google brings answers from a knackered thermostat to people saying the bmw 1/2 reading is rigged to stop people worrying about temp fluctuation, it says M cars give the true reading ads it goes up and down, the manual also says normal operating temp is normal unless the red part lights up......im confussed

I had an e46 M3 - the gauge stayed dead on centre like all BMW's. They are rigged so that minor fluctuations occur in a buffer zone where the needle doesn't move. If the needle moves the fluctuation is bigger than it should be.

Sounds like your stat is stuck open. Ive had it on 3 BMW's in the past - E46 330, e60 535d and e90 320d - all doing exactly what yours does and after the change, the needle stays dead centre again.

So many people have dodgy stats stuck in the open position that they think the fluctuating needle is normal, even heard a mechanic say it recently, but the bottom line is if it doesn't happen with a new stat then its clearly a fault.

Fairly easy DIY and cheap part too though.

[quote="mobilejo"]
I had an e46 M3 - the gauge stayed dead on centre like all BMW's. They are rigged so that minor fluctuations occur in a buffer zone where the needle doesn't move. If the needle moves the fluctuation is bigger than it should be.

Sounds like your stat is stuck open. Ive had it on 3 BMW's in the past - E46 330, e60 535d and e90 320d - all doing exactly what yours does and after the change, the needle stays dead centre again.

So many people have dodgy stats stuck in the open position that they think the fluctuating needle is normal, even heard a mechanic say it recently, but the bottom line is if it doesn't happen with a new stat then its clearly a fault.

Fairly easy DIY and cheap part too though.
[/quote]

if it is stat (my first thought) i put one in both my x5s, although i shit myself when the gauge went over half but as said not particuly high, i know a knackered stat can cause oer heat issues as if removed all together the car can get too hot, thermostat as said is about £40, just wanted some sort of idea, thanks

[quote="shadrack"]
[quote="mobilejo"]
I had an e46 M3 - the gauge stayed dead on centre like all BMW's. They are rigged so that minor fluctuations occur in a buffer zone where the needle doesn't move. If the needle moves the fluctuation is bigger than it should be.

Sounds like your stat is stuck open. Ive had it on 3 BMW's in the past - E46 330, e60 535d and e90 320d - all doing exactly what yours does and after the change, the needle stays dead centre again.

So many people have dodgy stats stuck in the open position that they think the fluctuating needle is normal, even heard a mechanic say it recently, but the bottom line is if it doesn't happen with a new stat then its clearly a fault.

Fairly easy DIY and cheap part too though.
[/quote]

if it is stat (my first thought) i put one in both my x5s, although i shit myself when the gauge went over half but as said not particuly high, i know a knackered stat can cause oer heat issues as if removed all together the car can get too hot, thermostat as said is about £40, just wanted some sort of idea, thanks
[/quote]

I would put money on it being a stat, as when my stats were stuck open, they sometimes went over the mid point but never overheated.

It could be the that temp sensor is giving bad readings, but if theres a pattern to it (see below) and not just random up/down, its more likely that the sensor is fine and the readings its giving are genuine.

The pattern is the car cools down when moving and getting cool air hitting the engine, but heats up when stopped at traffic. If you see that, then its probably going to be a stuck stat.