Valtra
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| posted on 4/3/08 at 06:47 PM |
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Filling water system ...leaky cap !!
Hi just filled my water system for the first time and as usual with seven types the rad cap is lower than the original Fiat it came off in relation to
the engine . now i'm stabbing in the dark a tad here, but basicly the expansion tank is as high as I can get it and I've probably over
filled it (above the tube inside that comes from the rad ) so water and anti freeze is now dripping from the rad cap as there is only a metal to
metal seal to stop it ....so how to proceed ? do I put a rubber seal in the rim of the rad cap? do I take some water out of the expansion tank untill
the level sits below the inner tube ?
does it matter that the engine end of the main water pipes are well above the level in the rad and potentialy above that in the expansion tank also
the water return from my heater is also quite high in relation to the level in the expansion tank if I have to drop the level.
sorry to sound a bit thick but all the water systems I've ever worked on the rad cap is the highest point.
Cheers
Ian
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daviep
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| posted on 4/3/08 at 10:20 PM |
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I'm a touch simple and so always need to start at the begining.
What did the radiator and cap originaly come from? Surely whatever they were previously fitted to had a pressurised system ( unless they are 100+
years old) in which case they should be water tight. So I don't understand why the cap and radiaitor would have a metal to metal seal? Are you
sure the cap isn't knackered/missing parts?
Davie
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Valtra
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| posted on 4/3/08 at 10:51 PM |
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Hi the Rad is a reconditioned unit blagged from Sercs when my friend worked there years ago and is from the Fiat 131 that my engine came from . the
pressure cap is brand new by QH for a Fiat 131 (amoungst others) . The pressure seal is watertight I would think but the expansion tank pipe comes
into the neck above the pressure seal It may be that my brand new cap needs another seal that is missing to seal the top edge.
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daviep
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| posted on 5/3/08 at 06:43 PM |
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If your expansion bottle is connected to the overflow pipe on the radiator then there is no need to mount it high (it doesn't do any harm)
The theory is that as coolant heats up and expands it is forced passed the pressure cap and in to the expansion bottle, I know this is obvious. When
the system cools down again and the coolant contracts any fluid which was expelled should be sucked back out of the bottle and into the radiator.
For this to work correctly the cap must be sealed above the overflow port (i.e. underside of cap to top of radiator neck) and also the end of the
overflow must be below the coolant level in the expansion tank.
If the hose is not below the level of the coolant or the cap isn't sealed or the hose leaks where it connects to the neck, then what happens is
that coolant gets expelled when the system is hot but as it contracts it is able to draw air back into the cooling system. If this happens then you
slowly pump all the coolant out and replace it with air.
p.s. Unless you have another fill point which is the hightest point you will not be able to fill the system above the height of the radiator neck,
which may not be as high as the cylinder head.
Some pics of your system would clear up any confusion
Davie
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Valtra
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| posted on 5/3/08 at 08:03 PM |
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So I'll need another fill point then as my expansion tank is above head height but the rad neck isn't so the top of the engine and heater
won't fill properly ....is that logical ? Time for a re-think me thinks
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daviep
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| posted on 5/3/08 at 08:58 PM |
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That was pretty much the same conclusion I came to.
Popular choice is a header tank c/w pressure cap located on the scuttle. This is Tee'd into the bottom hose and the and the thermostat bypass
retuns in to it to bleed air from the system.
Davie
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Valtra
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| posted on 5/3/08 at 10:25 PM |
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Mmmm Thanks daviep . I think !
I'll spend a few hours looking at it and scratch my head to see what I can make of it
cheers
Ian
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