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Discussion Starter · #1 ·
Hi, I have a 1.8L JH.

How should the cooling work? specifically when it comes to the expansion tank. I haven't seen the little hose squirting into the expansion tank.. should it? under what circumstance?

What would cause it not to?

Thanks!
 

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1990 Cabriolet, 2004 VW Golf TDI
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The water pump draws water into it, and propels it into the block, up through the head, and out the upper hose flange through the upper radiator hose, through the radiator, and the cycle continues.
Coolant also flows out the rear of the head into the heater hose, through the heater core, and back to the water pump. If the heater valve is closed, there is no flow through the heater circuit.

As far as I understand, flow out of the lower coolant hose from the reservoir is minimal. In some cases, the reservoir can also be considered an expansion tank. Excess coolant will travel out the top of the radiator into the tank, and out the bottom as needed. The system is self leveling.

Other than low coolant level, the only reason I can think of for coolant not flowing through the expansion line into the reservoir is a blockage either in the radiator, or the line itself.
 

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Discussion Starter · #4 ·
So Matty, should there be a constant flow from the expansion line to the reservoir? or intermittent depending on level? when I put a new water pump on I could hear air coming out the expansion line as coolant was working through the engine, but have not seen any flow.
 

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The small hose to the reservoir is so the air can be bled off. There is always a bit of air in the system. Once the air enters the expansion tank, it will stay in the tank. The lower hose just keeps the cooling system full. There is little flow because of the bleeder hose, but in reality, there is not much.

Almost all cooling systems have some type of self bleeding system. There are exceptions but you should always have flow, either a dribble or a stream, there is usually something.
 
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