radiator backflush

[ctrover]

whats the best way to backflush a series radiator with out removing it?I dont have a thermostat in if that matters.Thanks

[Tim Smith]

What do you mean by backflush? I've only flushed my cooling system with one of those cheapo hose adapter kits from autozone. Is that the same thing?

[greenmeanie]

Pull the radiator hoses. I usually do top and bottom and flush the radiator separately from the engine. Apply hose to bottom hose of radiator and hold on. You are looking for a hose that has high flow and not necessarily high pressure. Any sludge should comeout the top hose. After this apply flow in the normal direction. Alternate until the water flows clear. It helps to have run one of those radiator flush potions from Prestone first.

It also works best if you have the radiator out of the truck and laid flat.Whilst it can help a bit I find that flushing alone never really cures an overheating engine.

Cheers
Gregor

[Firemanshort]

The last one I flushed I took out of the truck and did it on the floor (as mentioned above). I also used a firehose - which is not recommended. I reversed the water flow through the radiator using a fairly low flow from the the hose (30psi @ 65gpm). The danger of the fire hose is that the pressure and flow could be too great and cause a good radiator to burst and leak. (A small modern fire hose can generate streams of 100psi @ 200gpm when attached to an engine - I think radiators are designed to operate around 5psi.)

The discharge was initially clear, but then something broke free inside the radiator and it blew out a wad of rust and muddy water ran for about 3 or 4 minutes and then it cleared out again.

I rinsed and repeated from the top side and only had a slight run of murky water before it cleared up. I went back an forth one more time to get clear water from both ends.

My purpose was to improve water flow through the entire cooling system to ultimately get more hot water in the heater matrix. (I flushed radiator and heater matix.) The flushing did not solve my problem. Ultimately, I discovered my problem in the form of a seperated and collapsed heater hose that was restricting flow - nothing at all to do with radiators or heater matrixes.

However, I am sure that the flush is good periodic maintenance on a 30 year old truck.