Radiator flush?

skiff1, Jan 21, 1:03pm
1996 Nissan Navara D21
2.7 L, naturally aspirated diesel
500,000 km
Five speed manual

Coolant looks like it was used secondhand out of Noahs Ark, when it was put in at the Nissan factory.
I would like to replace the coolant, and do a radiator flush at the same time. Any advice on a particular type of flush, or any other helpful hints?
Thanks in advance.

gunna-1, Jan 21, 1:46pm
Something with a corrosion inhibitor, i tend to use a rag and bung the garden hose in the top radiator hose to flush the block out, usually the block goes all scaly after that much neglect, if you pull the frost plugs out there will likely be piles of rust from the block that wont be dislodged easily, but a flush still wouldn't hurt.

m16d, Jan 21, 2:16pm
Its the top of the radiator cores that get blocked.
I used to go down to the local carriers wash down pad, and connect the high pressure hose to the bottom radiator hose and give it full blast for a minute or so. worked for me.

marte, Jan 21, 2:25pm
Cleaner, + rescaled as seperate cleaners.

Descaler is normally Ammonium phosphate, I don't know the concentration.
And cleaners normally Tartaric/Citric acid, is dishwasher cleaner.

But a quality automotive products always better, any liqui-moly product, or just OTC @ Supercheap auto.

Rinsie it all out, then fill with distilled water & run it for a day on that, then distilled water & coolant. If you use tap water + coolant, the coolant starts it's reaction on the impuritys in the tap water & shortens its life & usefullness.

franc123, Jan 21, 3:19pm
Difficult to offer advice without seeing the state of what's drained out of it. I would consider draining it and reverse flushing the radiator then refilling it with plain water and then drive it for a week and see how clean the water stays, repeat as needed until it stays clean. Then put say a 20% concentration of antifreeze in it and watch very closely for leaks for the next few weeks, particularly from the water pump.

msigg, Jan 21, 3:48pm
Yes as franc, reverse flush then leave it overnight full of some scale remover to soften then fust again. Or give it a birthday with a new core, looks like its done its service.

skiff1, Jan 21, 4:15pm
im in favour of a new core too, except this thing is just a back up wagon. The whole job would be lucky to be worth $2K so I’m willing to spend time but not money on the old girl. Logic is a radiator clean out now might save me a radiator, or a block/head later down the track.
She tends to do no km for six months, and then might do 2000 or 3000 km in a fortnight.

andy61, Sep 24, 4:51pm
Take the radiator to a radiator shop, and have it rodded out, I did that a few years back with a Mistral I had , did`nt cost much and is peace of mind knowing the radiator is not partly blocked. ( the Mistral radiator was not blocked as it turned out), The original radiators are way better than the cheap Chinese radiators available out there. My logic at the time was ensuring the cooling system was up to scratch as I did a bit of towing and didnt want any overheating, as it turned out I hated the Mistral and quickly changed it for a far nicer Terrano.