Looking for a BMW
AO Gold Member
Join Date: Nov 2008
County: Good old Sussex by the sea
There are at least five, maybe six hoses attached to the thermostat and you have to take them all off and all the hoses will contain the (same) coolant.
When cold, the system is not under pressure, if it was, all the coolant would all come out of the expansion tank when you take the lid off! However, you can do the job with a warm engine but doing the job when the engine is hot is not advisable, just let it cool down a wee bit.
The hose at the back of the themostat that you mention (there should be two of them), go to the heater matrix
To expand on why it is worth giving the whole system a flush, over time, your radiator (and/or other components) may have started to corrode and sludge or gunk, whatever you want to call it, will start to build up in the cooling system and circulate around and this isn't good. Sticking a fresh water hose in to all the orifices (oo-er!) will help to get rid of all that crud.
If you're not confident about tackling the job, get someone to help you - two heads and four pairs of hands and eyes are much better than one person getting frustrated on their own!
Last edited by Starkers; 07-12-13 at 11:08.
Reason: Added information