Astra J boiling header tank

[RJSB87]

Hi all,
I'm in desperate need of some help or advice.
I've a 2011 Astra J
I've currently got an issue with my header tank boiling over!
The Thermostat has been changed and also the temperature sensor.
The temperature sensor has also been replaced in the radiator.
With no faults showing as being present.
I'm still currently getting issues of it boiling back into the header tank, is this either the head gasket or the water pump and how can I determine the probable cause?
The car has been filled with coolant also as opposed to just with water.

[catman]

Have you checked that the fan actually comes on when it's hot? Did you do the work yourself? If so, are you sure that there are no air locks in the system?

[RJSB87]

I've had a mechanic friend sort it, I've tried to ensure I've got rid of the air locks.
The fan does come on, it's more reactive when I put the air con and the heat on full?
If I disconnect the harness cable from the thermostat cable I get a fault on the dash (service due) but I get continuous operation of the fan.

[littleredrooster]

Is it actually boiling, or is it blowing the coolant out because of lots of pressure? What does the temperature gauge read?

When it boils, turn it off and try to reach down to the bottom hose or the bottom of the radiator. Are they mad hot or cool? Does it continue to boil after the engine is stopped, or does it stop bubbling straight away? Can you hear it boiling in the head as well as the tank?

[RJSB87]

Hi...
It appears to be boiling, when I turn the car off it does slow the bubbling down in the header tank.
Both radiator hoses appear to be hot when I grab them also when I give them a gentle squeeze I do get bubbles up into the header tank.

[RJSB87]

The temperature of the car is at a constant 9p°

[RJSB87]

That was meant to be 90°

[gazza285]

Sounds like head gasket to me.

[oakdale]

One thing you must check on these before going any further, is to make sure water is flowing into the header tank from the small diameter pipe at the top of it when the engine is running.

If this degassing pipe or anywhere in the circuit is blocked, you'll get the symptoms you have.

[littleredrooster]

gazza285 said:

Sounds like head gasket to me.

Seems most likely diagnosis. If the whole system is very hot, too much heat is going into the water so that is the first suspicion. Sniffer test needed next.

[Martin30]

Could be as simple as a failed pressure cap on the expansion tank. Had that on my son's Peugeot 207, all the symptoms looked like head gasket but it was as simple as the pressure cap releasing the pressure in the coolant system much too early, thus the coolant bubbles and looks like it is boiling.

My problem was made much worse by buying a cheapy eBay cap that was also faulty from new. Replacement genuine Peugeot cap and everything back to normal.

Martin.

[silentbrown]

RJSB87 said:

Hi...
Both radiator hoses appear to be hot when I grab them also when I give them a gentle squeeze I do get bubbles up into the header tank.

Shouldn't get air bubbles, surely? Normally squeezing the hose should just raise the level in the header tank slightly.

The temperature of the car is at a constant 90°

Yet pure water at atmospheric pressure boils at 100. Coolant in a pressurized car system shouldn't boil much below 120, probably depending on coolant concentration and the the pressure cap.

Maybe worth plugging in an OBD reader and seeing what that says.

[Rufus Roughcut]

We had the same symptoms on my sons 12 plate Astra, we assumed the worst, turned out to be the pressure relief cap.

[robbie1990]

silentbrown said:

Shouldn't get air bubbles, surely? Normally squeezing the hose should just raise the level in the header tank slightly.

The temperature of the car is at a constant 90°

Yet pure water at atmospheric pressure boils at 100. Coolant in a pressurized car system shouldn't boil much below 120, probably depending on coolant concentration and the the pressure cap.

Maybe worth plugging in an OBD reader and seeing what that says.

90c on most cars dashboard will often be 80-100c

[E-bmw]

robbie1990 said:

silentbrown said:

Shouldn't get air bubbles, surely? Normally squeezing the hose should just raise the level in the header tank slightly.

The temperature of the car is at a constant 90°

Yet pure water at atmospheric pressure boils at 100. Coolant in a pressurized car system shouldn't boil much below 120, probably depending on coolant concentration and the the pressure cap.

Maybe worth plugging in an OBD reader and seeing what that says.

90c on most cars dashboard will often be 80-100c

Yep, you are right 90 degrees is between 80 - 100 degrees.

[silentbrown]

E-bmw said:

Yep, you are right 90 degrees is between 80 - 100 degrees.

...which is why I suggested an OBD reader!

[spikeyhead]

E-bmw said:

robbie1990 said:

silentbrown said:

Shouldn't get air bubbles, surely? Normally squeezing the hose should just raise the level in the header tank slightly.

The temperature of the car is at a constant 90°

Yet pure water at atmospheric pressure boils at 100. Coolant in a pressurized car system shouldn't boil much below 120, probably depending on coolant concentration and the the pressure cap.

Maybe worth plugging in an OBD reader and seeing what that says.

90c on most cars dashboard will often be 80-100c

Yep, you are right 90 degrees is between 80 - 100 degrees.

In order to keep drivers happy, the temperature display on the dash of most modern cars is programmed to sit at 90 degrees, right in the middle of the comfort zone so long as the coolant is above warm and below "do something right now!"

[subsea99]

Did you get this resolved with the car ?