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Bleeding the Coolant System

You will need:

We will start presuming the coolant system is empty, this method method will still work if it is full

Remove the radiator cap, and place the half bottle neck down into the top of the radiator (like a funnel), now wrap the rag around the join and use the tape (Duct tape is recomended) to secure the join and ensure a snug fit.

Fill the radiator with water pausing every now and then to add anti-freeze (the mixture should be approximately 70% water, 30% anti-freeze). Alternative mix the anti-freeze and water together in a larger container to the mix you want, then pour in to the radiator expansion tank. Once the water is up to the top of the bottle, let it settle for a minute or two. The bottle is going to act as a header tank as many parts of the system are higher than the radiator.

Take the needle nose pliers and use them to open the plastic bleed valve on the other end of the radiator, when water starts to emerge tighten it back up.


Now take and allen and unscrew the small bolt on top of the thermostat housing, and tighten it again once water emerges.


At the back of the engine there is a third valve that looks like a tyre valve cap, this should unscrew by hand, again until water emerges.

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Now top up the bottle and start the engine. With the engine running slighly open each valve again in turn to let bubbles of air escape (do not remove the caps as the water will be getting hot), tighten each valve when the bubbles stop.

Now get into the vehicle and turn the heater on full, now hold the accelerator at 2000-2500rpm whilst an assistant keeps the bottle topped up.

You should start to see bubbles emerging in the bottle.

Continue holding the revs and topping up the water until the radiator fan kicks in, this can take upto 20 mins or so. Now observe the bubbles rising in the bottle if they are more than 5 seconds apart then switch the engine off, remove the bottle and replace the radiator cap.

If the bubbles continue frequently after the fan cuts in, then it is necessary to wait until the bubbles become infrequent before switching the engine off

NB: Ensure that the bottle is kept topped up through out the procedure to prevent any air from re-entering the system


Illustration: Using a 2l pop bottle as a makeshift header tank whilst bleeding the coolant system

bleeding_the_coolant_system.txt · Last modified: 2016/08/18 20:27 (external edit)