Refilling cooling system

Refilling cooling system

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sunbeam alpine

Original Poster:

6,936 posts

187 months

Wednesday 18th November 2015
quotequote all
I'm face with replacing the radiator on one of my classics, a job I've never done before. The radiator itself doesn't have a filler cap - the only filling point seems to be via the expansion tank.

Can anyone suggest the easiest way to refill the cooling system?

Sorry for the numpty question!

PositronicRay

26,952 posts

182 months

Wednesday 18th November 2015
quotequote all
Pouring coolant into the header tank should do it.

However some engines have a definite procedure to avoid air locks. If you're unsure maybe worth asking on a marque specific site.

Viperz888

558 posts

157 months

Thursday 19th November 2015
quotequote all
Fill up the system through the expansion tank, leaving cap off.
Start engine, as it heats up the level will fall, continue topping up.
Might take 15 minutes for the thermostat to open.
When it seems to have leveled off, put interior heater on full, continue to top up.
When it has leveled off you're done, though it is good practice to check it after cooling down.

Agree with the point about checking for specific procedures, I know there is a specific way to 'burp' some old Subaru engines.

C70R

17,596 posts

103 months

Thursday 19th November 2015
quotequote all
Viperz888 said:
Fill up the system through the expansion tank, leaving cap off.
Start engine, as it heats up the level will fall, continue topping up.
Might take 15 minutes for the thermostat to open.
When it seems to have leveled off, put interior heater on full, continue to top up.
When it has leveled off you're done, though it is good practice to check it after cooling down.

Agree with the point about checking for specific procedures, I know there is a specific way to 'burp' some old Subaru engines.
This is absolutely sensible for 99% of engines, but always worth checking for specifics. Radiator caps are a bit of a rarity, to be honest. I can't remember owning a car with one in the past.

v8250

2,724 posts

210 months

Sunday 22nd November 2015
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One other tip that can be used for all cars. Know the combined volume of you radiator, pipes and heater matrix. Pre-mix this volume, fill the system slowly...if you still have any coolant mix remaining but the filler/header if showing full you know you have air in the system and need to continue bleeding the system until all coolant has been used. Simple but very effective.

tapkaJohnD

1,930 posts

203 months

Sunday 29th November 2015
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Vacuum coolant refill kit: EG http://www.amazon.co.uk/Draper-09544-Coolant-Vacuu...

Connect it by the expanding rubber neck (extra thicknesses supplied) to the expansion bottle or radiator filler neck.
Connect it to an airline and turn on.
A venturi causes a vacuum to form and suck out all the old coolant into a waste bucket.
Wait until the vacuum gets to -20 to -25.
Turn off tap, disconnect airline, connect tube to can of diluted coolant, turn on tap.
Vacuum in system sucks in the coolant unil the system is full.

Because of the low pressure, any bubbles in the system expand mightily, and then contract to very small when back to atmospheric pressure, and even smaller when the system heats up and pressurises, so no air locks.

There are other makers beyond Draper - that's just a convenient example.
John