Discussion
... or get a chamber pot.
Getting back on track, the first Alan, what do you mean by the expansion tank - do you mean the overflow/catch tank?
The expansion tank is supposed to be full. The overflow tank might get filled up a bit but then sucked back in under vacuum (if there are no leaks).
Could you post a pic?
Now - off to the pub to fill my bladder (eventually)
Getting back on track, the first Alan, what do you mean by the expansion tank - do you mean the overflow/catch tank?
The expansion tank is supposed to be full. The overflow tank might get filled up a bit but then sucked back in under vacuum (if there are no leaks).
Could you post a pic?
Now - off to the pub to fill my bladder (eventually)
In a normal RV8 cooling arrangement the expansion tank is usually a little over half full when the system is cold.
When the system is hot, the water expands and providing there is no air trapped inside the cooling system, one expects that the expansion tank will begin to fill with coolant. Usually full, but not to overflowing.
At the same time the air in the expansion tank will be expelled by the expanding water IF and AFTER the internal (air) pressure exceeds 15 psi (typically).
The longer the journey, the more likely air will be expelled and as the pressure builds up so the boiling point of the fluid also increases, so, providing the thermostat, radiator and fan are doing their job, maintaining temperature just below 100 deg C, the water never actually boils and no steam is produced.
Therefor you observation,
On the other hand if water and/or steam is being expelled from the expansion tank overflow, then three things come to mind.
1 The expansion tank is too full. RTFM to establish how full it should be at top-up. Usually such overfilling is self correcting anyway.
2 There is air trapped inside the cooling system (block) that is locked in and cant escape. That air prevents water cooling from taking place locally and the engine develops hot spots thereabouts. These immediately turn any local coolant to steam, over-pressurising the system and sending coolant and/or steam to the expansion tank where it is forced out of the pressure cap, even though the system actually contained less fluid than it should have. To solve this problem you have to exclude all air locks at top-up..
3 A small, even insignificant, head gasket problem over-pressurises the cooling system with combustion gasses and can usually be detected by a small but constant stream of baby bubbles entering the expansion tank. The problem can be mitigated by fitting a temporary overflow tank to catch any expelled fluid and allow it to be sucked back on cooling.
CLICK HERE to solve all problems.
When the system is hot, the water expands and providing there is no air trapped inside the cooling system, one expects that the expansion tank will begin to fill with coolant. Usually full, but not to overflowing.
At the same time the air in the expansion tank will be expelled by the expanding water IF and AFTER the internal (air) pressure exceeds 15 psi (typically).
The longer the journey, the more likely air will be expelled and as the pressure builds up so the boiling point of the fluid also increases, so, providing the thermostat, radiator and fan are doing their job, maintaining temperature just below 100 deg C, the water never actually boils and no steam is produced.
Therefor you observation,
mac123yre said:
the expansion tank seems to fill up with water after a long run
to my way of thinking, is what one might expect.On the other hand if water and/or steam is being expelled from the expansion tank overflow, then three things come to mind.
1 The expansion tank is too full. RTFM to establish how full it should be at top-up. Usually such overfilling is self correcting anyway.
2 There is air trapped inside the cooling system (block) that is locked in and cant escape. That air prevents water cooling from taking place locally and the engine develops hot spots thereabouts. These immediately turn any local coolant to steam, over-pressurising the system and sending coolant and/or steam to the expansion tank where it is forced out of the pressure cap, even though the system actually contained less fluid than it should have. To solve this problem you have to exclude all air locks at top-up..
3 A small, even insignificant, head gasket problem over-pressurises the cooling system with combustion gasses and can usually be detected by a small but constant stream of baby bubbles entering the expansion tank. The problem can be mitigated by fitting a temporary overflow tank to catch any expelled fluid and allow it to be sucked back on cooling.
CLICK HERE to solve all problems.
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