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Old 13th September 2020, 20:05
cbjroms cbjroms is offline
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Default Cooling System Problem

So I am running a Herald 13/60 engine in my (Sammio) kit car. The top of the radiator sits lower than the thermostat housing due to the shape of the bonnet. So, in the hose which connects the bottom of the radiator to the thermostat housing I have added a T piece, one limb of which is connected to an expansion tank. The expansion tank sits slightly higher than the top of the thermostat housing.

I was out in the car this afternoon and noticed that the temp guage was reading very high. First thought was that the temp controlled radiator fan had failed but that all checked out fine. Then I noticed that the radiator felt cooler than anything else and that the expansion tank was bubbling. I carefully removed the pressure cap from the expansion tank (it was full to the top) and lifted it higher above the engine. There was a gurgling noise, the level in the tank dropped back to normal, the radiator heated up and the fan kicked in.

I had presumed that with the exapnsion tank being higher than both the thermostat housing and radiator, any trapped air would make its way to the expansion tank. But today, the air seems to have collected in the radiator. What am I missing?

Last edited by cbjroms; 14th September 2020 at 18:31..
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