Quick Coolant Change Question

[tom325sport]

I've just copied and pasted this from the Wiki...

My question is just after number 8 below. Do I put the header tank cap back on before I start the engine or can it be left off until I've finished bleeding?

Coolant Change

1. Loosen off and remove the cap on the header tank (On RHS next to wing). Check the surface of the coolant for an oily film. If there is one the head gasket could be on the way out.
Move the heater temp control to fully cold to prevent air locks in the heater matrix
Also check that the bottom is yellow and rated at 140.If not go to the dealer and get one. (they were subject to a recall years ago as the originals weren’t up to the job)
2. Undo bottom hose from radiator at RHS of the car, let coolant drain (catch it in a bucket and dispose of properly)
3. Undo the 3x 10mm bolts on the thermostat housing (at the front of the engine, in front of the distributor cap) (may need to remove small fuel hose to access one of the top bolts)
4. Remove thermostat, and check its ok (should be closed if cold) If in doubt an new one is £9.99 from GSF/ECP. Bolt housing back together.
5. Insert hose into header tank (next to RHS wing) and flush system until water is running clear.
6. Remove top hose (LHS) from radiator and flush through with hose until clear
7. Replace the thermostat, and reattach all hoses
8. Pour the coolant into the header tank (located on RHS next to wing) SLOWLY and give it time to settle. (should take about 4.5l to get to cold level marker)
9. Set the heaters to full (HOT and no. 4 fan setting, open all vents) and start car.
10. Let car idle for 5-10mins keeping an eye on the temp gauge
11. Open the 8mm bleed nipple (on top of the thermostat housing) and allow air to escape, then close.
12. Repeat bleeding until all air is out and only water comes out when bleed nipple is opened. Top up if required.
13. Get a cup of coffee and relax for 20 mins

[daimlerman]

I bleed with the cap on...

When filling,I 'borrow' the kitchen 1 litre measuring jug...pour in a litre of antifreeze,followed by two litres of water,repeating until full.This ensures plenty of walking between the tap and the car,so it allows the air to be pushed out.

Do not forget to remove oily paw marks from the measuring jug and the kitchen taps!

[tom325sport]

Good tip that Malc!

So fill until its in the header tank, then cap on, then start engine and wait till warm?

[capri_rob]

Did it with cap off the other day - thats how I've always done it on other cars.

Bleed screws can seize or snap so give it a blast with WD40 or penetrating oil well before you intend to try and undo it

Also not sure whether it matters much but I understood when filling the system but before starting the car the heater should be set to hot AND ignition on to allow the water to flow through the matrix - with the ignition off the heater valve doesnt open.

[hongkongfuey]

When re filling, i undo the bleed screw, it releases trapped air at the highest point. Then tighten, top up till expansion tank is full, squeeze front pipes, to get rid of more air, start engine, squeeze pipes, then open the bleed screw , repeat until satisfied no more air, put cap on , check heat inside car, take round the block, top up as needed

[Brianmoooore]

Few mistakes in the above!
All references to RHS should read LHS. Left and right of a car are as viewed from standing behind it.
Heater temperature control should be at hot during the whole procedure. The default position of the electric heater valve is open, so it doesn't actually matter while the ignition is off, but if the knob is at full cold, and the ignition turned on, there will be no circulation through the heater system and airlocks are likely to occur.
Not really necessary to remove the thermostat to change the coolant.
The correct way (on an M20) is to remove the block drain plug hidden behind the rear of the exhaust manifold, but I just settle for removing the bottom heater hose at the bulkhead, and connecting a hosepipe to the hose (NOT heater stub).
It's important that the coolant cap has been changed (on 1.4 bar models only), and a yellow base to the cap indicates that it has been, BUT, apparently there are replacement caps out there with black bases as well.
You won't get the full amount of coolant into the car, because the block will be full of clean water.
You need to add between 33% and 50% of the total capacity of the system of neat coolant, and then continue topping up with water.
When starting the car, have the fan on speed 2, so that you can be sure to feel the first vestiges of heat coming from the heater, indicating you don't have an air lock.
Finally, it doesn't matter if the cap is on or off, as long as it doesn't start pushing coolant out of the neck. Obviously, to get the system up to pressure and check for leaks, the cap will have to be on,

[tom325sport]

Did it with cap off the other day - thats how I've always done it on other cars.

Bleed screws can seize or snap so give it a blast with WD40 or penetrating oil well before you intend to try and undo it

Also not sure whether it matters much but I understood when filling the system but before starting the car the heater should be set to hot AND ignition on to allow the water to flow through the matrix - with the ignition off the heater valve doesnt open.

Cheers Jim - Bought a new one from BMW anyhow as the other one had had it!

[tom325sport]

When re filling, i undo the bleed screw, it releases trapped air at the highest point. Then tighten, top up till expansion tank is full, squeeze front pipes, to get rid of more air, start engine, squeeze pipes, then open the bleed screw , repeat until satisfied no more air, put cap on , check heat inside car, take round the block, top up as needed

Good tips here thank you!!

[tom325sport]

Few mistakes in the above!
All references to RHS should read LHS. Left and right of a car are as viewed from standing behind it.
Heater temperature control should be at hot during the whole procedure. The default position of the electric heater valve is open, so it doesn't actually matter while the ignition is off, but if the knob is at full cold, and the ignition turned on, there will be no circulation through the heater system and airlocks are likely to occur.
Not really necessary to remove the thermostat to change the coolant.
The correct way (on an M20) is to remove the block drain plug hidden behind the rear of the exhaust manifold, but I just settle for removing the bottom heater hose at the bulkhead, and connecting a hosepipe to the hose (NOT heater stub).
It's important that the coolant cap has been changed (on 1.4 bar models only), and a yellow base to the cap indicates that it has been, BUT, apparently there are replacement caps out there with black bases as well.
You won't get the full amount of coolant into the car, because the block will be full of clean water.
You need to add between 33% and 50% of the total capacity of the system of neat coolant, and then continue topping up with water.
When starting the car, have the fan on speed 2, so that you can be sure to feel the first vestiges of heat coming from the heater, indicating you don't have an air lock.
Finally, it doesn't matter if the cap is on or off, as long as it doesn't start pushing coolant out of the neck. Obviously, to get the system up to pressure and check for leaks, the cap will have to be on,

Again Brian thank you! Can anyone update the wiki do you know? Maybe worth updating this?