Pressure cooling system 740

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Rock - 25 Jan 2005 16:44 GMT

When a 740 is started from cold and left to idle how long does it take for
the system to start to receive pressure, 20 seconds 30 seconds.

If the engine is then stopped after one minute would there be pressure at
the pressure cap on the cooling reservoir

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jg - 25 Jan 2005 19:59 GMT

> When a 740 is started from cold and left to idle how long does it take for
> the system to start to receive pressure, 20 seconds 30 seconds.
>
> If the engine is then stopped after one minute would there be pressure at
> the pressure cap on the cooling reservoir

The only immediate pressure would be from flow resistance after the pump and
very slight. There won't be any real pressure until it reaches boiling temp,
however long that takes. Then the pressure is obviously all through the
system & should remain until it cools some, much longer than 1 minute more
like 15 or 20. Just squeeze a hose to know if the system is pressurised.

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James Sweet - 26 Jan 2005 02:43 GMT

The pressure is roughly linear with the coolant temperature guage on the
dash, when it reaches operating temperature it's pressurized.

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Mike F - 26 Jan 2005 13:21 GMT

> > When a 740 is started from cold and left to idle how long does it take for
> > the system to start to receive pressure, 20 seconds 30 seconds.
[quoted text clipped - 4 lines]
> The pressure is roughly linear with the coolant temperature guage on the
> dash, when it reaches operating temperature it's pressurized.

So if you're getting pressure after 20 or 30 seconds, then you have a
head gasket problem.

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Mike F.
Thornhill (near Toronto), Ont.

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