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How To 'burp' A Car's Cooling System - Engine/Ancilliaries - The Lotus Forums - Official Lotus Community Partner Jump to content


How To 'burp' A Car's Cooling System


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Last weekend I decided to have a look at my cooling system as it was reading increasingly hotter each day of driving. The radiator was recored two years ago and I have done the water pump efficiency test - all with good results. The thermostat check out (but I removed it anyway)

In Queensland, Australia you can be forgiven for thinking the climate is a contributing factor with most days over 32 deg for the last 5 months. In my case, it was a red herring.

I decided to flush the system and refill with water and water-wetter. We don't need anti-freeze here.

The following week the car system boiled - much to my horror. (head - not the head!!)

I check the surge tank level and all was ok. The radiator was warm - so flow was happening - but what was wrong?

I rang my Lotus guy and he said 'had I burped the engine?'. I said that I had ran the engine with the garden hose attached and squished a few hoses etc. He said 'Jack up the bum of the car a good foot, and run the engine from cold - ready with a supply of water'

I did, and as predicted, two litres of water dissapeared into the car. Since then, the car runs like a dream.

Nice tip - didn't know that.


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Iain, not sure if yours is the same as the later waterpumps but if you have removed the thermostat you may need to re-install it. There could be a diverter valve attached which ensures all the water coming out of the engine goes to the radiator. Without it heated water can get bypassed back into the engine.


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By raising the height of the swirl tank (by jacking the car up) , you are making it the highest part of the cooling system.

As you probably know, air tends to pocket at the highest parts of the cooling system, so by having the swirl pot open at the raised level, the trapped air will migrate out making gurgling and or burping noises in the process.

The heater core / top of the radiator is where your extra 2 litres of coolant ended up.

On the Turbos, there is also a bleed valve on the radiator (upper left side) which is behind a cover in the front comparment which also is used to bleed out trapped air.

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Def agree! Anti freeze IS a major rust inhibitor, put it back in!

Ethelene Glycol AF is also highly toxic.. consider using Propylene Glycol AF instead.

Also recommend doing a litmus test periodically to make sure the coolant is neutral PH.

Use distilled water as the water component of the cooling system, where possible.


If you set no goals you shall surely reach them..

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Thanks Danny,

Good fact sheet - and I do like nulon products.

The conflict in information is actually from my Lotus guy, who says not to use glycol products - just distilled water and 'water wetter'.

I usually put glycol in anyway, just for the anti-corrosive protection.


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