So mine makes a hissing noise when loosening the cap but it doesn’t raise or lower the level have you had the heaters on when you’ve been driving?, does it over heat because mine kept trying to over heat when it had air in it
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Bleeding cooling system?
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dontknowz
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- Joined: Fri Oct 06, 2023 10:05 pm
- Engine size/power: 2.0 TDI (140bhp)
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BenT
- 100BHP+
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- Joined: Fri Nov 19, 2021 9:26 pm
- Engine size/power: 1.6 CR TDI (102bhp)
Re: Bleeding cooling system?
BenT shouldnt it be slightly pressurised when opening the cap after letting it cool down over night?
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If nothing's entering or leaving the system the pressure should be constant, for a given temperature. So, if the system's at atmospheric pressure when cold it should stay this way unless something's getting into the system to pressurise it further. If you depressurise the system when cold, drive it, then let it cool down full y there shouldn't be any noticeable pressure increase at all.
Thinking about it though, if you do have a pocket of air trapped in the system somewhere, this will compress as the system heats up and may cause the coolant level to drop until the system cools down again. Is the coolant level always correct when the engine's cold, and just low when warm? If the level's always the same when cold then either you've got some rogue air somewhere that's being compressed OR you've got a bulge in a coolant pipe somewhere.
[/quote]
If nothing's entering or leaving the system the pressure should be constant, for a given temperature. So, if the system's at atmospheric pressure when cold it should stay this way unless something's getting into the system to pressurise it further. If you depressurise the system when cold, drive it, then let it cool down full y there shouldn't be any noticeable pressure increase at all.
Thinking about it though, if you do have a pocket of air trapped in the system somewhere, this will compress as the system heats up and may cause the coolant level to drop until the system cools down again. Is the coolant level always correct when the engine's cold, and just low when warm? If the level's always the same when cold then either you've got some rogue air somewhere that's being compressed OR you've got a bulge in a coolant pipe somewhere.