[Mk2] [Turbo] Engine slow to heat up? Or dodgy temperature gauge?

[wizzer]

I've had all my engine work done now and got a stainless tubular exhaust manifold and downpipe. I've noticed that it now seems to take *ages* for the temp gauge in the car to get up to half way (i.e half an hour down a motorway and it's still pretty close to the bottom). Left longer it does eventually reach half-way and stays there, at the proper place. I can't believe that my engine is really now running super-cool as i can see a heat-haze over the top of the engine cover.
The temp gauge runs off the the sensor fastened to the engine cover i believe - is it possible that this is broken (has been ok for a while!).
What else could cause this?

Thanks
James

[skinthespin]

Sounds like a dodgy thermostat mate, it will be stuck open, taking ages for the engine to get up to temp, especially on the mway when you have a cooling flow of air all around the car.

if its running cold it won't do your engine any favours either, promoting engine wear.

HTH

[Slarty]

The best test is to take it for a drive around town so the engine is getting plenty of heat into it, without the air flow over the radiator. 20 minutes is enough I reckon. Then park up somewhere with the engine running. If it comes up to temperature within a few minutes, set off and try and find a clear A road or something. If the temp then comes back down again, it's a screwed thermostat.

When my one failed (about 7 months or so ago!) it hadn't actually jammed open, the inner part had become detatched from the outer, allowing coolant to flow through at all times. Hard to describe but it'll be very obvious when you take it out.