Could my thermostat be stuck open?

[Steve _T]

Since her service my Chim has been running colder than ever. I remember before she went in, if I did my normal run on the A3, temp would never reach 70, but hover around 60-65. Post the service, with lip spoiler re-attached and a new radiator, the temp is now down in 50s on the same run and never rises above this. This is for a journey time of around 30 mins, speed of 60-70mph for most of the journey. Temp does reach 90 in traffic, fans work as normal and so on. Is this standard behaviour and I'm being paranoid, or alternatively could the thermostat be stuck open?
Assuming the thermostat is stuck open, is it a job that a relative mechanical novice should steer clear of or not? If a garage do it, what would a reasonable price be?

Thanks all,

Steve (and Bright Yellow Chimaera 5L)

[.mark]

If you have a splitter fixed I would expect it to run cooler, especially as you say the temperatures is normal (90) in traffic?

[Nobby]

Yes it is stuck open or missing, if it's working it sould warm up to at least the mid 70s...

[ATG]

Sounds like it is stuck open. You could probably test this by starting the engine and feeling how hot the radiator hose is getting. It should stay cold for a while then quickly get hot as the valve opens. If it warms up gradually then chances are the valve is stuck open. I think Steve Heath's book describes taking the valve out and putting it in hot water so you can see it opening.

[Bob the Planner]

Sounds like the problem I had and discussed on Winter Temperature www.pistonheads.com/gassing/topic.asp?t=4683&f=8&h=0&hw=temperature
I don't know the fix as I had mine sorted at the dealers under warrenty.

[Steve _T]

ATG,

Thanks for the tip, was trying to think of a suitable means to assess the state of the thermostat, obvious when you think about it. Checked today and the stat appears to be working, since as described, the hose warmed up all of a sudden while she was ticking over on the drive way.

This leads me to believe that the temp gauge is being affected by airflow at speed, causing it to read low. I also established that the hosing into the radiator was leaking a bit, so tightened the jubilee clip a bit more. Is it possible to over tighten them? Anyway, a step closer to perfect running and a lot less concerned. I reckon I did about 400 miles this weekend and all plain sailing (scratch one VX220 and one Z3M - unlucky chaps).

Thanks again,

Steve (and Bright Yellow Chim')

[Popester]

Steve,

Did you ever find out what was causing the problem. My 5L has also taken to weird temeprature readings after a recent service. Used to run between 70-90 degrees, now never shows over 70 and often the needle barely moves. The fans are still kicking in so I suspect temperature is still as it was before and that I have a gauge/sender problem. Curious to know what your diagnosis was.

[Steve _T]

More recently the temps have been hovering around 65-70 so probably just the colder air at that time of year. I reckon the sensor is subject to airflow affecting its operation. Only issue now is one of my fans stopped spinning, hence temp got as high as 100 recently. She's never done that before, so I reckon the sensor is reasonably accurate in still air. A couple more hours in the footwell and I might sort it.

Cheers,

Steve