I recently checked my oil and water and found that the radiator filler neck was clogged with orange gunk! My car has been off the road for 17 years but it has always had antifreeze in it and not just water, which i changed about 3 moths ago. I've now done 400 miles and checked the radiator a month ago and it was clean.

Could this be head gasket? There is no creamy gunk under the oil cap or dipstick, the car doesn't smoke or over heat.

Because it's orange could it just be rust out of the water ways that has eventually worked it's way out after being stood for so long?

The day before it was 30 plus degrees and I took the car out for some exuberant driving so wondered if the engine got a bit warmer than normal.

I flushed the gunk out and I've done 30 miles since and the gunk hasn't re appeared.

Any ideas?

Was the colour of the coolant you dropped prior to the change different to what you added? Some will have remained in the system

Nissan coolant is green, could be condensation and rust, my coolant has always been changed and came out clear green but when I took the water pump off the other day, car has sat for a Year now being restored it was very rusty was clean in 2019.

Edited July 2Jul 2 by Bones28

OE 48 Anti freeze is good for around 2 years so i am not surprised you have corrosion.

So do you think mine will be corrosion instead of the head gasket? I'm going to flush it out at the weekend and see how it goes.

If the HG was gone you will know very quickly.On a TT within seconds of any boost the cooling system literally empties out the overflow !

Ah, I see. I've been on boost no problem and the temperature sticks at half way on the guage, no over heating. I'll flush her out at the weekend and report back, thank you.

Quick update. Everything thing seems fine. It must of been the accumulation of 17 years of old antifreeze sat in the engine. Flushed it out every thing is fine.