help with engine temperature and heaters plz

[Leighton Wood]

i bought my galaxy about 3 months ago and notice that the temperature gauge stays at the bottom end of the scale (0) it literally doesnt move unless im going up a steep hill it will then go to the half way point but never further but within a minute of level driving again it will return back to zero and it does it quite quickly too, literally within 10 seconds it from half way back to zero, but also noticed that the heaters are affected too. it takes ages to get any heat about 15 minutes and even then its not brilliant, when i park up or stop at lights it starts blowing cold air again
im thinking of changing the thermostat in the hope that it will fix this (i will be having a go myself as i found thread on here how to do it) but im open to any suggestions or help as i dont know much about cars 

[johnnyroper]

That sounds like a faulty thermostat to me,if it's stuck open or opens too early with a PD engine especially with a large cooling system like the galaxy you will struggle to get much heat.

Change the thermostat and fill With fresh coolant and I reckon all will be good.
Also from what you are saying I suspect your boost heater is not working either? And probably the run on coolant pump?

[Leighton Wood]

just an update today almost overheated no heating at all now just freezing cold air and the temp gauge went up to 1 bar before the red and then slowly back to 90 where it seems to be staying now. oh and the expansion bottle is almost full? no idea why since i know it was only at the max mark when i topped up a few weeks ago
ill be changing the thermostat either today or tommorow and praying

[johnnyroper]

Check the water pump impeller is not spinning freely on shaft,this can be done when stat is out by sticking finger in the hole.
Also check the little plastic restrictor in return pipe to expansion bottle is not blocked.
The no heat but nearly overheating does point towards head gasket issues in my opinion but you need to check the basics first.

[Chrispb]

You may even find there's no thermostat in it, in that case someone has already had overheating issues with it in the past.