Hi all, can someone explain to me what the purpose of a coolant bypass hoses are?

A the back of the engine ?

 

To bypass the heater matrix if its leaking.

These ones https://conceptzperformance.com/nissan-infiniti-nissan-oem-coolant-bypass-hose-nissan-300zx-z32-14055-f6511_p_1000.php

 

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Ah,

 

They are not bypass as you would think.

 

They join the front aluminium water pipes to the block.

 

When the water gets up to temp the valve opens and lets water flow to the radiator.

I see, i had them replaced but i have leak under the block im convinced that the leak is from those hoses, this happens on startup whilst the engine is cold any ideas?

 

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Could it be possible that when the pipes heat up and expand it seals the leak slightly.

It leaks even when engine is warm, leak is actually worse when engine is up to temp

 

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