Head Gasket or something else?

Had my first overheat issue today
Was heading up a steep hill in Queenland australia (was about 30c).
Carefully monitoring my OBD gauge as well as temp gauge and saw engine climb to 110C. The gauge got to about 3/4 but was flicking up and down to its usual spot just below half. The OBD temp was flicking between 110 and 103C. When i go to the top it started to boil over.

Got a tow home and bled the cooling system and things seem settled again. Issue seems fine on freeway just comes up in traffic or big hills.

Things I have been observing
- I had noticed this flicking of temp previously. I re-bled the cooling system a week ago thinking I might have air. There was a little that came out but not much.
- The oil filler puffs smoke when you rev the engine. like its the oil breather isnt working? - i have had some weeping of oil out of the filler over the last month.
- There is no indication of water in oil or oil in water.

This car has had 2 head gaskets done before me - really dont want it to be this again.

If it continues I will take it back to my MG mechanic - fixing these MGs are expensive over here so would happy to hear anything I could check before hand.

First thing you might want to do is replace the coolant filler cap,these things are notorious for failing in fact get two and carry the other as a spare.
A cooling system pressure test might be a good idea, and a compression test to give you piece of mind.
Do you have a low coolant alarm? if not why not, running these ( or any modern car) with out one is insanity, there are a few types available. I have the Brown & Gammons low coolant alarm, a brilliant piece of kit, easy to fit and reliable.
You might check the cooling fans are working properly, a dodgy relay is a possibility here as well as the wrong cooling sensor could be used.
The thermostat could be the cause of your woes.
I fitted my car with a pair of extra cooling bay fans at the top engine bay vent, these were from a quad bike, they push heaps of seriously hot air outta the boot vent and work off the existing engine bay cooling fan wiring circuit. I did a write up of this on this forum some years ago, you might wanna check the old threads on here to find it.

it's a pity you're not down here in Melbourne, I'd be able to easily sort this issue out for you.

@Cobber . Yes , I agree with all of that and I also carry a spare header cap .
Ps , nice fan mod , love it .

Looks like its not a good story for it. Started it up today and definately smoke coming out of the oil filler.

Must be HGF blowing into the oil galleries

get a compression tester on it and see?

Crankcase normally runs in a low pressure condition due to connection to inlet manifold, so a blocked crankcase breather will give similar indication

I have tested removing sparkplugs and seems like cylinder 1 is the problem. I see less obvious smoke coming out without a spark plug in this cylinder.

It also seems to do it more at idle. if you rev the engine the smoke basically stops.

Also at idle I am seeing bubbles coming into the filler tank. but only at idle.

Could it be a liner?

Took the water pump off and it turns out to be part of the thermo housing broken off and stuch in the impellor.

Hopefully when I get back together it will be much better!