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Discussion Starter #1
Hey there,

My 307's coolant level when engine is cold is literally just above the MIN line. I haven't yet checked it when its warm but cant find any information in the handbook as to what the level should be & at what temp, e.g. to check when hot or cold? I have found general information saying the level needs to be near MAX when cold, in-between & also just above MIX.

I pulled this from a Peugeot site but it wasn't specifically about the 307:

"Look for the MAX–MIN levels on the side of the expansion tank, the coolant level should be at or above the MIN position. It is important not to overfill as coolant expands when hot and may cause problems if there is no room for this to occur in the expansion tank"

But another video on a Peugeot site contradicts this (again not specifically about the 307) & says it needs to be at MAX. :confused:

Am I just not seeing it in the handbook?

Thanks!!
 

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It's always advisable to wait until the engine has cooled to open the reservoir, as the coolant system pressurises when the engine is warm, so you may get a blast of air and coolant once you loosen the cap.

The coolant reservoir, when filled to the MAX line, is designed to allow for expansion of the fluid, so even if you fill the reservoir up to the max, this shouldn't cause any problems with expansion/pressure build up.

Personally, I'd keep it topped up to the MAX, as a minimum level may not be enough to regulate everything under certain conditions.

Hope this helps
 

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Discussion Starter #5
I noticed that when cold it is just above the min line (& I mean cold after a nights sitting) & when warmish - not even up to operating temperature, maybe 10 minute drive? it is almost at max!
 

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Explanation:

1. When the engine is cold and the level at MIN, there is a "reserve" in the tank which serves to replace any lost through leakage. Replacement only happens as the engine cools, and the reserve is drawn back into the system. Therefore checking the level when hot is not meaningful, as it will always be above MIN (unless loss has occurred in the previous cycle).

2. As stated earlier, if the cold level is at MAX, the normal expansion when hot will not result in the tank overflowing.

3, It therefore follows that having more than MIN in the tank (when cold) gives a greater reserve, which can only be a good thing.

There is an exception to point 2: If the cylinder head gasket has failed, and cylinder pressure is entering the cooling system, coolant can be forced out of the tank overflow valve. However, the answer is to fix the gasket, rather than running with the cold level below MAX.
 
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