80 Series Landcruiser Query

[80series93]

Firstly hello all, I am new here. I've been searching for an answer to my 'issue' for a few weeks now but can't quite find a post with indentical symptoms or info. So decided to join this forum seeking some advice. I am pretty switched on with mechanics so I fear I already know what the answer to my question will be. But here goes.

I have an 80 series land cruiser with the 1fz-fe engine. It runs and drives like a dream and has been fantastic. Never has it overheated or given any grief. Services always been a breeze. Recently however I have noticed a development of sludge/grime on the radiator cap every time i remove it. I have checked the over flow and it is clean. No apparent loss of coolant or engine oil and the 'sludge' has a chemical-like smell to it. I have not added anything to the cooling system other than coolant.

So i guess my question is, is there need for concern? It runs just shy of 80 degrees (aftermarket water temp gauge) and only breaches 80 under load or sometimes when off road. Never enough to be concerned. No sign of milky residue in the sump. No issues with performance and not running any differently. And still has fantastic oil pressure. It has done a lot of kms (445,000).

So i am wondering what others would recommend trying before jumping to any irrational conclusions. I am going to change the coolant and flush the system as well as change the engine oil and filter to see if results return in the radiator.

Should i be concerned? Where should i look first off? This is my first land cruiser, prior its always been patrols.

All topics ive read prior to this only speak of sludge in the overflow container. Which is why i wonder if my problem could be different.

Appreciate any info or assistance. Hoping to sort it over the xmas break!

1fz-fe manual transmission.

Cheers!

[trentmeyer23]

Give it a good flush and keep an eye on it.

Are you in a high dust area?

[80series93]

Thanks for the response.

No I live in a suburban area. The car has been through mud and crap previously however.

Going to flush and change today and see how i go.

Thanks!