Head Gasket??

[Soenvious]

Hi again,
My latest problem is loosing coolant from the system. Historically this car has overheated, when the pipe from the water pump split and lost all its fluid.
I've not driven very far but when I do the temp gauge sits around 90 and the coolant tank doesn't boil over. However over a couple of days it loses around 1/4 litre of water, with no leaks showing under the car. There is also a slight misfire when idling (could be plugs, don't know their age).
Checked system with blue fluid head gasket tester and this showed yellow, confirming a leak.
Question is are there any odd quirks with this engine that could give these symptoms, or is it head off time?
I guess I already know the answer but any thoughts would be appreciated.

 

[Soenvious]

It sounds like I'm answering my own question BUT, just found a post on youtube with a guy showing problems with core plugs leaking on this engine. He reckons he's replaced two, which were mis-diagnosed as head gasket failure.
That gives me something else to consider.

 

[Pedro]

Coolant temp at 90 is normal the misfire codes are P1336 multiple misfires across all cylinders & P1340 specific misfire also possibly coil pack/packs & or plugs are nearing end of life confirming a head gasket would mean plug/plugs getting wet coolant oily residues in expansion tank which again means misfiring regarding a blown gasket you may need to also check cylinder compressions leak down test for leaking exhaust valves/ worn piston rings etc
Lastly the most common coolant leak suspect is the Thermostat tank they eventually split in the seams but you need to be sure before your start throwing money ata it for no reason

 

[Soenvious]

Iwas

Coolant temp at 90 is normal the misfire codes are P1336 multiple misfires across all cylinders & P1340 specific misfire also possibly coil pack/packs & or plugs are nearing end of life confirming a head gasket would mean plug/plugs getting wet coolant oily residues in expansion tank which again means misfiring regarding a blown gasket you may need to also check cylinder compressions leak down test for leaking exhaust valves/ worn piston rings etc
Lastly the most common coolant leak suspect is the Thermostat tank they eventually split in the seams but you need to be sure before your start throwing money ata it for no reason

I was feeling a bit pessimistic but now you've tipped me completely over the edge haha!
Checked fault codes, non showing and plugs look a decent colour, not wet or oily.
Compression test next, then leak down, following your thoughts.
Is the thermostat tank the octopus thing on the end of the block?