MK5 Golf GTI

All Things Mk5 => Mk5 General Area => Topic started by: bower on May 29, 2014, 10:49:07 am

Title: broken thermostat?????
Post by: bower on May 29, 2014, 10:49:07 am
my bothers passat is showing signs of a duff stat as when driving its not getting up to temp, but had it plugged in vcds and when stationary it gets to 90c and stays there but when start driving it drops to 70c  :confused:

is this a sign that the stat needs replacing? and why does it get to 90c if its stuck open?
cheers for any advice
Title: Re: broken thermostat?????
Post by: Viking on May 29, 2014, 11:18:29 am
The thermostat simply regulates the temperature by opening and closing to keep the coolant at 90°c. It doesn't affect how much heat the coolant absorbs from the engine. So if the engine gets hot then the coolant gets hot.

The stat should be closed initially so that the engine warms up to 90°c, and will then open/close as required to keep it at that temperature. If it's stuck open then the 90°c will still be achieved (albeit a longer time to get there) and then the cooling fans/water pump will keep it at 90°c and stop it overheating. When you're driving the coolant is still circulating round the system and radiator, and the cool air coming in through the grille will cool it down. This is when the stat should be closed to stop it cooling, but your faulty stat is stuck open so doesn't regulate the temperature correctly.
Title: Re: broken thermostat?????
Post by: bower on May 29, 2014, 11:33:03 am
thanks viking that made things clear  :happy2:
looks like im now off thermostat shopping
Title: Re: broken thermostat?????
Post by: GrayMK5GTI on May 29, 2014, 05:11:04 pm
If it helps. . .

http://www.mk5golfgti.co.uk/forum/index.php/topic,80793.0.html