Pressure in expansion tank

[Sheldon13]

Hi All

Need some info.

I recently purchased a new expansion tank cap from dealers and also replaced the radiator and a pipe that was leaking coolant.
After replacing the above i noticed that there is built up pressure in the expansion tank. Built up meaning that if the car is driven the night before and i open the expansion tank cap the next morning, there is pressure in it and a little coolant starts to shoot out..
Is this correct?

The car does not heat up and cools as its supposed to.
In traffic the temp goes up to abt 105 and goes down to about 99 when normal driving.
When accelerating hard it drops to about 83

The car is an E90 320i

 

[Waseem 333i]

Surely it's got to do with bleeding the cooling system. Holding pressure overnight should not happen. Try bleeding it again. If it's the same then visit Silverton radiators to check if head gasket is okay.

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[Don1]

Sounds like a blown head gasket. Get a cylinder leakage test done to confirm if this is the case

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[Sheldon13]

Thanks for the reply guys.
Wouldn’t a blown gasket blow off white smoke through the exhaust and water levels will go low.
The car is not taking any water and no smoke through the exhaust


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[Yuben]

+1 on bleeding the system.

Regarding the temps, it could be a faulty thermostat.

 

[M135i]

Is there a milky substance underneath the water bottle's cap or anything mixed with the water other than the antifreeze?

 

[Sheldon13]

No milky substance on the expansion tank cap or oil cap.
Temps are correct and what the car is supposed to be running at according to what I have read.
What is the correct bleeding method.
Car is E90 320i so it doesn’t have the electric water pump.


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[shailesh]

Sounds like a blown head gasket. Get a cylinder leakage test done to confirm if this is the case

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+1 on the blown head gasket. :thumbs:

 

[Don1]

What is the mileage on this vehicle

 

[Sheldon13]

What is the mileage on this vehicle

Current mileage is at 204k kms

Also have to state that the heater in the car has also stopped working after the radiator was changed

 

[D_CPT]

What is the mileage on this vehicle

Current mileage is at 204k kms

Also have to state that the heater in the car has also stopped working after the radiator was changed

Definitely an issue with bleeding the cooling system - heater not working just confirms this.

Your cylinder head gasket is fine bud seeing that there's no oil mixing in the water ( milky residue).

Let us know once you've had the coolant system bled, the procedure is floating around on the forum. :thumbs:

 

[Sheldon13]

What is the mileage on this vehicle

Current mileage is at 204k kms

Also have to state that the heater in the car has also stopped working after the radiator was changed

Definitely an issue with bleeding the cooling system - heater not working just confirms this.

Your cylinder head gasket is fine bud seeing that there's no oil mixing in the water ( milky residue).

Let us know once you've had the coolant system bled, the procedure is floating around on the forum. :thumbs:

Cool man..thanks alot for this..
Will try and search for the bleeding method

 

[Nella11]

Your cylinder head gasket is fine bud seeing that there's no oil mixing in the water ( milky residue).

Not necessarily unfortunately
You can have water mixing with oil and you'll get that milky residue
Or it can push water into the combustion chamber and it will use a lot of water
Or it can push combustion gasses into the water system causing a pressure build up in the cooling system. This can also unfortunately means a cracked block or head.

The cooling system is a closed system. ..if it heats up it obviously will build up a pressure. ...but as soon as it cools down again there shouldn't be any pressure
Just my 2c

 

[Sheldon13]

Update :
So i had the cooling system bled and the heater worked thereafter.
Also seems to be no pressure in the expansion tank and the car is definitely not heating up or taking water.

All seems to be good for now