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Discussion Starter #1 (Edited)
Hi everyone,

My upper radiator hose gets firm when the engine reaches operating temperature. It is firm but not hard. It is still squeezable to some extent (about 4 to 5 centimeters).

I am worried about this. Does my cooling system have higher than normal pressure?

Also worth mentioning:

1 - My car doesn't lose any coolant
2 - The temperate gauge is always within normal range
3 - No overheating issues
4 - No air in the system
5 - Engine runs fine and pulls nicely
6 - Thermostat runs fine
7 - No oil in coolant or coolant in oil
8 - No bubbles in coolant at the radiator filler neck whether the engine is cold or hot
9 - Radiator cap was replaced 2 years ago

The engine is XU7JP4 LFY.

So, why my upper radiator hose is not soft to the touch? Is my headgasket blown? Should I tear the engine apart?
 

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HI...to me no1 to no9 means all is well...dont look for problems....the coolant systerm will be under pressure anyway when its at the right temp
 

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Discussion Starter #3
I should also say that the hose was soft to the touch before i replace radiator cap. After replacing it got firm.

Does it mean that the faulty cap didn't allow the pressure to build up in the system?
 

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1.4 bar is correct for your car, dont replace it with one with less pressure. At 1.4 bar the hose will feel hard so all ok..:thumb:
 

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Discussion Starter #9 (Edited)
1.4 bar is correct for your car, dont replace it with one with less pressure. At 1.4 bar the hose will feel hard so all ok..:thumb:
You are right. But there is something I don't understand. Why Peugeot has chosen such a high pressure radiator cap for a normal passenger car?

Peugeot 406 1.8 is not a high performance car like a Ferrari or Porsche!

Most cars use around 13 PSi pressure caps. Even a 10 PSi pressure cap can still increase boiling point to the extent higher than needed in a passenger car.

1.4 bar = 20.3 PSi! That's extremely high for a 406 1.8!

The boiling point of my car's coolant = 110 °C

Can someone please explain the reason behind using a high pressure cap for a city car like 406?
 

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Hi...I hope you find the answer to the cap pressure,but if your car was designed with it...and it runs ok...what are you trying to achieve?I would class the 406 as a motorway mile muncher not a city car but does both well...enjoy your car...
 
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