Bleeding cooling system...


When I start my Sporty from cold, I can hear the water "gurgling/bubbling" from under the dashboard, meaning I have air in the system (radiator was changed just before I bought the car).
What is the method for bleeding the system?


Bleeding cooling

After I changed my thermostat, I also had air in the system.

When the engine was cool, I took the rad cap off and started the engine. When the engine started to get warm, the stat opened and pushed the water around the system and let the air bubbles come out.

Also, make sure your heater lever is on hot in the cab, as it allows water to circulate around the heater matrix.

I also kept squeezing the 2 heater pipes for around 5 minutes, and did the same with the other water pipes, as this forced the air out through the radiator.

After a while there were no more bubbles from the rad.

I couldn't find a bleed point anywhere, possibly its supposed to bleed itself?

It did the trick anyway,

Sound like the heater matrix is leaking.

Bubbling from below the dash when the engine is cold is a sign that the heater matrix is leaking. Coolant leaks away from the matrix overnight and drips onto the carpet. Check for any damp patches on the carpet below the radiator and sides of the transmission tunnel. When the engine starts the water pump forces water into the matrix and you hear the void being filled by coolant so bubbles get forced from the matrix. No doubt you will discover the water level in the overflow reservoir has reduced.
There is no 'bleeding system'. Just run the engine which forces any air into the expansion tank.


You may want to do a leak test on the cooling system. Pressurise it for an hour or so - and then confirm that its not the head gasket blowing into the water ways!

Heater matrix

Yes. The heater matrix is leaking if the carpet is damp/wet after the engine has cooled overnight. More than likely you will feel water driping below the radio whilst the engine is running. The damp patch is usually down the side of the tunnel below the radio.
There is no fix. It has been known for the matrix to be by-passed. The two pipes entering the matrix can be seen behind the engine at the base of the balkhead. Problem with a by-pass is that you will have no heater/demisting in winter.
If your a diy you can buy mail order a replacement matrix from motorrads of Redditch [about £60]. Use the search option above and search on 'matrix'. You will get the details/telephone number and some facts about replacing the matrix.
Dont attempt a matrix repair - a waste of time. They rot. They take quite some time and effort to replace. Its not difficult - just takes time and small hands!. Get a replacment matrix.