When was the coolant last changed? I've seen something similar when the coolant colours were mixed together and they make a paste similar to what you see in your pic.I was heading away for a nice relaxing weekend (worked all over the festive break.) I got about 20km from my destination and noticed I was overheating.
Limped it to camp minus the camper and dropped the water. At this stage the engine was making a really weird ticking noise I put it down to the fan belt. Tried the next day and same thing it overheated within a few minutes. Limped the car to a zone where I could be towed (I was in the hills and out of my racv zone and no cash to pay the 500 they wanted to get me) I had to let it hit the H a couple of times as I was in a to dangerous position to pull over. I let the engine cool before proceeding again. dropped the oil and fluids today. No milk in the oil or metal that I can see. However some percular things in the cooling system.
The water is flowing in a pulse like state not constant. Fluid is flowing out both pipes of the heater lines when I run the car. Block one the other flows out.
It has also started to become difficult to start and shoots a ploom of smoke. I'm convinced it's white Mrs is convinced it's black.
I have Attached video.
Some precursor info. I had a weird noise start a few months back. Took it to my mechanic and he said it's the fan belt. I sprayed the fan belt with belt conditioner (I think that's the name. It's not belt grip but similar) and noise dissapeard. Repeated this several times.
I took the side round piece off where the top hose to the radiator connects and found a disformed diaphragm maybe? (pic attached)
View attachment 549429
View attachment 549430
Just trying to diagnose some things before sending to mechanics.