Recently got a '94 F-150 with a 302. Wasn't having problems with cooling but the cooling system had obviously been neglected, a lot of rust-scum deposits visible on surfaces looking down the filler neck and the coolant was very dirty. I've been flushing with multiple products - Prestone, Thermocure, trisodium phosphate, Metal Rescue (rust removal product), CLR. Each time using a burping funnel to make sure it's filling the system, and each time draining the radiator and disconnecting the lower radiator hose to drain the engine as well and following up with a distilled water flush - numerous times when I did the TSP flush until I no longer saw any foam from the TSP.

After many, many flushes as described above the water when viewed in the burping funnel is quite a bit improved - by eyeball estimate when filled with distilled water only it's probably 75% - 80% clearer than it was originally - but still not tapwater clear. I find there's still a visible sludge on the inside of the radiator when looking down the fill neck. It's not hard and adhered to the surface, it comes off when you run a plastic stick over it. With all the cleaning products I've had in there and the turbulent hot water I'm really surprised none of them removed it.

Is it possible to get the radiator pristine clean while in the vehicle without having it hot-tanked at a radiator shop?

 

 

That or a hot tank job.

 

I see what you're trying to do but just a word of caution, all of those chemicals you keep putting in there can end up doing more damage than you want. Have you tried disconnecting the upper and lower hoses and just blasting water through the radiator in both directions with a garden hose?

 

Me, personally, I do a drain and fill of 50/50 premix coolant every fall that way my radiator and water passages stay clean....

 

That won't help him since he recently bought it already in this condition.

 

Get a new radiator.. You want pristine? You are not going to be able to do that.

The real concern now, is that you added all of those chemicals into the cooling system. You even allowed all of those chemicals to flow into your engine block. You need to be more concerned about flushing out your engine block & getting rid of those harsh solvents & cleansers, which will mix & react with the coolant, and cause unforeseeable damage in the future. Let's think about that. If TSP were meant to be in the cooling system, then it would be an ingredient in the coolant. And we would all be adding it directly into the overflow tank so that it can flow into the engine block. It's not harmless, like adding a raw egg to fix a leak.

While you're at it, get new hoses, replace the thermostat, install a new water pump, and a new belt.