Stovebolt.com Forums The Shop Area The Engine Shop Radiator question

It’s been so long since I’ve worked old trucks I’ve forgotten everything.
Radiator and cooling system as a whole has lots of rust in it.

Any suggestions on a way forward to clean some or all of the rust out.

Clean it as best you can by flushing the system with water.

Open petcock on radiator (and engine block if it can be done without breaking it) and let engine run while simultaneously filling the radiator with a garden hose as it drains from the system.

How do you know the system has lots of rust? Are you assuming so or can you see crud in it?

If it's really bad with lots of solid rust particles in there, then take the radiator out rather than risk filling it with debris.

Remove core plugs from engine block and blast with high pressure water and poke scrapers in there, etc.

Other guys on here have filled the entire cooling system with Evaporust and run the engine until the chemical has broken down all the rust over several applications.

Remove the heater core from the equation to avoid filling the system with any rust that might be in it. Clean that separately.

It's nearly 70 years old, with a questionable service history. It has rust in the cooling system!

Good advice on cleaning it out.

You can also drain all the water out of the radiator and engine (this will let you know if your rear drain plug is stopped up), remove your water pump, close your rear drain plug and fill the block up to the point it is dribbling over a bit at the water pump opening with C-L-R. Probably will take about 2 small bottles. Let it sit two nights or so and drain out the rear drain plug in your engine into a bucket. If your engine is really sludged up, get a coat hanger, straighten it and put a 1 inch or so bend at the end and then work it around through your water pump hole back to your rear cylinder (that's where most of the crud will have gone) to dislodge it and then use C-L-R. Some folks have used citric acid (you can buy this in solid crystal form on Amazon). I take it they just mixed it strong (maybe 50/50 water to citric acid) and poured it in the block and then flushed it. I haven't tried that but the C-L-R will work if you're patient.

I filled it up and drained it and no slug or rust came out.. maybe the rust has been in there so long it solidified.

I'm going zero pressure since I've plugged some leaks with JB weld as a short term measure..

water pump seems to work ok.. it shows good flow at the radiator so that is one less thing to worry about...

Thanks for the tips guys..much appreciated.

Fill it with water only and leave out the antifreeze. Drive it for a while and see what comes out when you drain it again. No sense wasting antifreeze. You can add it in the winter.

You might also try the Evaporust method that some other people have used. Fill the system with Evaporust and nothing else and drive it for a couple months and drain it out and flush it when it turns black

Tdoug Got a lesson on rodding the radiator tubes with a Briggs and stratton recoil starter spring, when the guy got done he would take a garden hose and a shop rag,fill from the bottom. Water would come right up and when he let up would just gush back out the bottom ! Fixed it !!

Wouldn’t he have to remove one of the tanks to rod it out?

Phah 1 Yes took the top tank off,he often re-cored wreck damaged radiators. He would get it on edge and use a flame with about a foot long feather,solder would run out on the floor till the tank came off. It's very important to get the solder channel and tank edge clean,so the tank will set bottomed out in that channel when it's soldered back up.