Radiator cap - Mineral deposit?

My 1997 Super Custom 3l 1 kzte has been running a bit hot over the summer. On longer runs in 35+ degree heat I feel limited to < 100kph as the temp guage (digital dash) starts to climb especially noticeable up hills where I limited myself to 80 sometimes to keep the temp mid range. Not into the red zone but 1-2 up from centre
i.e. [][][][][][x][x][][]



I now see the following deposits in my rad cap, it's not leaking fluid, nor loosing any coolant and there is no evidence in the engine oil of any rad fluid as it is clean.



I have just completed a radiator flush and refill, should I still be worried, or am I just being too careful from all the other posts on this forum regarding overheating and cracked heads! Would be nice to go faster than 100 on hot days if you think it can take it!

Cheers, any advice appreciated!

The coolant that you put in was already red? Or did you put in green or blue?

This picture was from before the radiator flush?

More in general it would be good to replace this cap (in my case it just let a lot of coolant out, it opened way too early) and then check the hoses for cracks. Or if they have become bigger. Then you should replace them.

Do you hear the visco fan being activated when you're driving up the hill for example? You should hear it when things are getting hot.

I can hear it clear when activates, but I have a 2L engine (2.4 non-turbo diesel). It activates way before temp goes high.
I have used it in 40 degrees Celcius summer weather driving it up the hill without any issues. But a turbo diesel produces more heat.

If all fails and you keep having issues, you could try a radiator fabricating/repair company. They could fit a thicker radiator having more cooling capacity.

And yes the 1KZ is prone to head cracking, so you shouldn't push it as you already know.

This pic is from before the flush (Done yesterday). The previous coolant was replaced last year with Red Nulon long life, I'm not sure of the exact coolant in there before then, but it was red!
The cap was replaced last year too, so I've given it and the spout a good clean to help ensure the seal. Hoses were also replaced last year.

The viscous fan runs and increases revs with engine, if it increases enough I am not sure?

Had it at a mates garage yesterday to check it out and do the flush. Interestingly the Super Custom has loads of fitted guards/plates under the engine bay restricting airflow (I guess for noise damping/protection?) so we have now removed them to see if it makes a difference to cooling.

Cheers

Well I'm not sure but I think the visco fan of the 1KZ works the same way like my 2L visco fan. That means if the temperature goes above a certain point, the visco fan is "enabled" and you can clearly hear it spinning up. It then makes quite some sound, which you will also here on the highway regardless of extra driving noise.
There has to be sufficient cooling liquid inside though, because of there is not enough cooling liquid it might not work. But you had it filled, so it should be good.

I'm not sure but maybe you have an issue with the visco fan?