filling cooling system

[timthetinyhorse 0]

im replaing th thermostat on my 9A this weekend and was wondering how i go about re-filling the cooling system once i am finished, i know water can be put in the expansion tank but does it have to be blead through or anything?

[davidwort 0]

I think the main tip is to refill very slowly (into the expansion tank), this helps prevent airlocks, it needs to dribble in really slow, take 5-10 minutes over it,

and mix the coolant and water first and add a litre at a time, then you know exactly how much has gone in and how much more will be needed if you do get an airlock.

Once you've got all you can get in, hopefully at least 4 or five litres before the header tank doesn't drain down any more, then run the car till warm/thermostat has opened fully (wait till fan comes on), let it cool pretty much fully and it should expell any air into the expansion tank, i.e. the coolant level will drop a bit, it shouldn't need more than a cupfull if you originally refilled slowly.

If you rush it you can get big airlocks that can be a bugger to remove.

[VR6 0]

Not sure if it's different on other cars but on the VR I've filled via the rad top hose and never had any problems before.

[vwdeviant 0]

I think the main tip is to refill very slowly (into the expansion tank), this helps prevent airlocks, it needs to dribble in really slow, take 5-10 minutes over it,

and mix the coolant and water first and add a litre at a time, then you know exactly how much has gone in and how much more will be needed if you do get an airlock.

Once you've got all you can get in, hopefully at least 4 or five litres before the header tank doesn't drain down any more, then run the car till warm/thermostat has opened fully (wait till fan comes on), let it cool pretty much fully and it should expell any air into the expansion tank, i.e. the coolant level will drop a bit, it shouldn't need more than a cupfull if you originally refilled slowly.

If you rush it you can get big airlocks that can be a bugger to remove.

 

Just to add to this I found best way to fill via the header tank was to use an old plastic coke bottle with a hole in the cap, means it fills slowly enough to avoid air-locks and you can leave it "stood" in the tank's neck while it drains... saves aching arms!

[A1 VR6 0]

Also set the heater to the hot position so that the heater matrix fills up otherwise you can get an airlock there.

[davidwort 0]

Also set the heater to the hot position so that the heater matrix fills up otherwise you can get an airlock there.

 

:) don't make any difference, no valve in the matrix, it's all done with air flaps.

[davidwort 0]

 

Just to add to this I found best way to fill via the header tank was to use an old plastic coke bottle with a hole in the cap, means it fills slowly enough to avoid air-locks and you can leave it "stood" in the tank's neck while it drains... saves aching arms!

 

I was trying to remember your tip, definitely a good idea :salute:

[Kempy 0]

whats the best way to flush the system? Ive just fitted a new thermostat and dont really wanna have to take that off, I want to find out if my rads past it to, what can I do for that? ta

[davidwort 0]

whats the best way to flush the system? Ive just fitted a new thermostat and dont really wanna have to take that off, I want to find out if my rads past it to, what can I do for that? ta

 

stat blocks the system when cold so you do really need to remove it, it's worth just running the car with fresh water and draining a couple of times after getting up to temp and letting the stat open.

You could always take both rad hoses off and flush both ways with a garden hose from the mains pressure.

I prefer not to use coolant flush additives as they can dislodge stuff that may have built up over time and then may partially block a waterway or rad tube.