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Overpressure in cooling system


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Ok, I am going to try to explain my problem in english...

Today I took out my car for the first run after the "winter rest" Its a 996 GT3 Mk1. After a couple of hours of driving when I stopped by my friend och saw a pretty big cloud from the rear.

It was water from the cooling system. My friend who is a pretty godd mechanic told me that I have "overpressure" in the cooling system.

Anyone know what my problem is or have experienced anything simular?

Thanks guys

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The cooling system will be under pressure after a drive. Did you happen to notice the reading on the temp gauge?

Yes

But the overpressure valve is realising and the system cant hold the water, and its porring out from the overflow bottle so this is not right

Edited by Smr
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The cooling system will be under pressure after a drive. Did you happen to notice the reading on the temp gauge?

The temp gauge were at a normal level.

The overpressure made that "secureity pin" to pop upp and it came out water from the lid

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It could be many things, and should probably be checked out by a mechanic since any local overheating can cause metal or gasket damage. Something you said caught my eye, though. You said that the "security pin" had popped up. Might you be referring to the domed plastic device on top of the coolant reservoir near the filler cap? It has a wire bail/handle on the top in sort of a rectangular shape. It is normally roughly horizontal. If you lever it up to vertical, it lifts a plastic pin through the top of the dome. The purpose of that assembly is to vent excess air out of the cooling system, usually after a drain/refill cycle. The 996/997 cooling system is virtualy horizontal, front to rear, allowing lot of places for air pockets to form. Air pockets may equal uncooled places and uneven cooling or localized overheating. So, it's important to be able to vent excess air and can done with the motor running/hot. Anyway, the normal position for the wire bail is horizontal. In vertical/vent mode, it may even allow hot coolant to escape....and, maybe cause steam clouds as the coolant hits hot things.

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It could be many things, and should probably be checked out by a mechanic since any local overheating can cause metal or gasket damage. Something you said caught my eye, though. You said that the "security pin" had popped up. Might you be referring to the domed plastic device on top of the coolant reservoir near the filler cap? It has a wire bail/handle on the top in sort of a rectangular shape. It is normally roughly horizontal. If you lever it up to vertical, it lifts a plastic pin through the top of the dome. The purpose of that assembly is to vent excess air out of the cooling system, usually after a drain/refill cycle. The 996/997 cooling system is virtualy horizontal, front to rear, allowing lot of places for air pockets to form. Air pockets may equal uncooled places and uneven cooling or localized overheating. So, it's important to be able to vent excess air and can done with the motor running/hot. Anyway, the normal position for the wire bail is horizontal. In vertical/vent mode, it may even allow hot coolant to escape....and, maybe cause steam clouds as the coolant hits hot things.

The car is not overheating, all temps are normal....But the car has allot of pressure in the coolant system..The over pressure valve is realising and are opened when the car is stopped and there is a lot of pressure in the system, the car has not been worked or any thing and air doesnt get in the system by it self...

As i understand the vent pin should always be in "down" mode when driving and only "up" when venting the system

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It could be many things, and should probably be checked out by a mechanic since any local overheating can cause metal or gasket damage. Something you said caught my eye, though. You said that the "security pin" had popped up. Might you be referring to the domed plastic device on top of the coolant reservoir near the filler cap? It has a wire bail/handle on the top in sort of a rectangular shape. It is normally roughly horizontal. If you lever it up to vertical, it lifts a plastic pin through the top of the dome. The purpose of that assembly is to vent excess air out of the cooling system, usually after a drain/refill cycle. The 996/997 cooling system is virtualy horizontal, front to rear, allowing lot of places for air pockets to form. Air pockets may equal uncooled places and uneven cooling or localized overheating. So, it's important to be able to vent excess air and can done with the motor running/hot. Anyway, the normal position for the wire bail is horizontal. In vertical/vent mode, it may even allow hot coolant to escape....and, maybe cause steam clouds as the coolant hits hot things.

Yes its that "plasticpin" I mean.

So do you mean that its normal that the plastic pin is "pushed up" eventhough wirebail is horizontal? This happends when the engine is at a normal temp.

Thanks alot for your help :clapping:

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The plastic pin, on my car, protrudes from the plastic dome about 8mm, even when the engine is stone cold. Levering the bail up will raise the pin even more. But, I'm still confused by the symptoms you describe.

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The car is spitting out water also becouse of the high pressure, it not from the overflow bottlecap but from the vent cap...the hoses are very hard and there is to much pressure in the system and the vent cap cant realinsing it all...

Im thiniking a stuck termostat or something like that...

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The plastic pin, on my car, protrudes from the plastic dome about 8mm, even when the engine is stone cold. Levering the bail up will raise the pin even more. But, I'm still confused by the symptoms you describe.

Yes but his is all the way upp like when you pull it upp...and there is no arir in the system he has vented it like 20 times and the pressure is there .....And there has been no work on the car so it shouldnt be any air in the system....

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  • 3 months later...

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