Chevy 350 - Flushing Cooling System

[Dan in Pasadena]

It's an early 70's block. In my '46 truck - see avatar. Already drained radiator & refilled w/ water twice, still depleted coolant & slight rust.

No heater in truck. A plug in top of eater pump and T-stat housing bolts appear ancient and rusty. MUST I remove Tstat to power flush? Can I plumb a hose connector into that water pump plug location? Any experienced advice appreciated, Dan

 

[regguy1]

It's an early 70's block. In my '46 truck - see avatar. Already drained radiator & refilled w/ water twice, still depleted coolant & slight rust.

No heater in truck. A plug in top of eater pump and T-stat housing bolts appear ancient and rusty. MUST I remove Tstat to power flush? Can I plumb a hose connector into that water pump plug location? Any experienced advice appreciated, Dan

Some early blocks had a 1/4" pipe plug on each side, near the bottom between the soft plugs. I can't say when this might have been discontinued.

Put anti freeze mix in it.....IMO (and the generals: GM)

 

[Dan in Pasadena]

Of course I have every intention of using a water/coolant mix. I just put water in it while trying to flush it. I've not noticed those block drains, I don't think it has them. I THINK I'm gonna have to take the chance of breaking those
thermostat housing bolts then with the T-stat out, force water through the water pump via the garden hose. Other advice?

 

[regguy1]

Of course I have every intention of using a water/coolant mix. I just put water in it while trying to flush it. I've not noticed those block drains, I don't think it has them. I THINK I'm gonna have to take the chance of breaking those
thermostat housing bolts then with the T-stat out, force water through the water pump via the garden hose. Other advice?

When you mentioned rust I thought maybe it had water for extended time...

If those bolts break you might have enough of a stub sticking out of the manifold to get a vise grip on..?? Grind a flat on 2 sides for better grip

 

[Red Green]

If its only slightly rust colored still I would just fill the radiator and drain it a couple more times. Rather than trying to get out the old bolts. It takes about 5 times to get most of the antifreeze out of the block in my racecar in the spring.

 

[srmofo]

Just hook the garden hose up to the top radiator hose. Hob cobble an adapter together and use a hose clamp then slowly turn the hose on. It should build enough pressure to push the tstat open. then let it run

 

[regguy1]

Just hook the garden hose up to the top radiator hose. Hob cobble an adapter together and use a hose clamp then slowly turn the hose on. It should build enough pressure to push the tstat open. then let it run

Thermostat will be closed, not much water will get through I dont think water pressure will push it open

 

[930dreamer]

I'd fill it with water, drive it to normal temp, cool a bit and drain. Repeat until clean.

 

[Dan in Pasadena]

I'd fill it with water, drive it to normal temp, cool a bit and drain. Repeat until clean.

That's EXACTLY what I was trying to do but did it three times and it was still coming out orangish. Wondering if the old coolant was that hot yellow stuff that goes a bit orange as it dies? Top tank now looks clean.

I agree my garden hose isn't gonna open a thermostat and I probably SHOULD pull the T stat and make sure I've got a full clean flush before putting in all new Prestone/water mix. But if what "Red Green" says is correct and 'm only a couple more fills away I should probably try that first. One issue, the rad bottom tank has a brass plug, NOT a petcock. So to pull it when its hot I put a plastic glove/leather glove/towels wrapped up my arm lying on by back and have to move FAST to keep from getting scalded. So far so good.

 

[srmofo]

Thermostat will be closed, not much water will get through I dont think water pressure will push it open

Our reverse flush machine is regulated to 18 psi and it opens it. Thats why it has to be reverse of normal flow. But it has adapters that we clamp on. Thats the key. Im sure something could be rigged up in the plumbing section from HD or lowes.

 

[Dan in Pasadena]

Our reverse flush machine is regulated to 18 psi and it opens it. That's why it has to be reverse of normal flow. But it has adapters that we clamp on. That's the key. I'm sure something could be rigged up in the plumbing section from HD or Lowes.

IF I could do it without all the drama of possible broken bolts, etc it would be so much better...for now.

To do it as you do it, where do I hook up the inlet and outflow? I agree, I can rig something up if I understand how it's supposed to work.

 

[srmofo]

Ill take some pics today of the adapters. On a350, the coolant flows in the bottom and out the top.the easiest place to tap in is the upper hose at the radiator. The adapter just slides into the hose and clamps tight. Leave the radiator open. Your adapter just needs to connect a water hose, where mine connects to the machine. I would put a valve on yours to regulate flow easier than at the spicket.

 

[Dan in Pasadena]

Thanks a lot, really appreciate it! - Best, Dan

 

[JimH]

I always pulled the upper hose at the radiator and started the engine. When it warms up the t-stat opens and then just keep the rad full with the garden hose. Just take it easy with the garden hose or you'll cool it down and close the stat.

 

[Lippyp]

Over here you can get specific cooling system flushing chemicals, the best is a two system one, flush, fill with clean water, put the first part in, drive it around for a bit, drain, flush, refill, put part two in to neutrailse part one, drive around, drain, flush and then refill with new coolant, removes way more baked on crud than just flushing with plain water.

 

[Dan in Pasadena]

I always pulled the upper hose at the radiator and started the engine. When it warms up the t-stat opens and then just keep the rad full with the garden hose. Just take it easy with the garden hose or you'll cool it down and close the stat.

Good idea, and simple. YOu let the dirty water come out the top hose/radiator outlet or you also open the bottom of the radiator?

Over here you can get specific cooling system flushing chemicals, the best is a two system one, flush, fill with clean water, put the first part in, drive it around for a bit, drain, flush, refill, put part two in to neutrailse part one, drive around, drain, flush and then refill with new coolant, removes way more baked on crud than just flushing with plain water.

Oh, we don't have that here in the colonies (Kidding)
I haven't been over to an auto parts store to see what they've got. I got busy on Monday and didn't go back to working on the truck so its sitting with plain water in it (getting rusty!) I'll get back to it this weekend. Right now I am thinking I will try a couple more fills/drains of my radiator to see if I can get the water to come out clean. If that doesn't work then I will shift to Lippy's idea of pulling the top hose - it looks kinda ratty anyway and I'll replace it when I put new coolant in it.

Thanks everyone.

 

[c_mccann]

light muriatic acid solution?? Use it on heat exchangers with great results for removing calcuim and rust traces..

 

[JimH]

Let the **** come out the upper hose until you see clear water, then shut it down and drain the rad and fill it with straight coolant, usually ends up about a 50/50 mix.

 

[Dan in Pasadena]

I've got three gallons of pre-mixed Prestone 50/50 coolant...not sure that will be enough but I can easily get more if I need it. The main thing is getting the spent/rusty coolant all out of it.

 

[FastKat]

I saw you mention something about a coolant tank? If you have a steel overflow tank, take it off, fill it about halfway with water, add some sand (play sand will be fine) and shake it hard for about 5-10 mins. The sand will act as an abrasive and get a lot of the rust off and out. That will take care of one source of rust.

 

[Professur]

Dan, premix is good for topping off, but for filling, it's a bad idea. You'll always have water left in the system, and that's going to dilute your coolant mix to way under optimal.