So I decided to change my coolant and flushed all the old stuff out. I picked up 3 gallons of Fleet Charge low-silicant antifreeze from TSC, which meets ASTM D4985 standards. A lot of you probably already know this but I figure these pics might help someone out. I hooked up a garden hose to the block where the heater core normally attaches and removed the lower radiator hose. It wouldn't come off and I was getting frustrated so I just cut it but I wish I hadn't because I cost myself 20 bux right there... At least I'm glad Autozone had it.

You'll need 5/8" heater hose and a female garden hose end (also 5/8"). I think I got pretty much all 6 gallons of the old coolant out. By the end clear water was running through the system. I also forward flushed the heater core and radiator. The radiator looks pretty corroded on the inside and from the looks of the water pump outlet (see pic) there's a fine layer of orange rust all the way around. I don't think the previous owner ever changed the coolant. Although when I did the voltmeter test the coolant didn't come out bad. Does that rust in there look typical?

I was debating whether I should use Preston Super Flush but I didn't want to loosen up gunk and have it clog somewhere in the cooling system. What do you guys think?

The flush says to pour it in with fresh water and let the engine come up to normal operating temp. but I'd have to drive the truck around for several miles to get any heat. Would it be safe to drive around with just water and the flush in there?

 

i have used the bg coolant flush with great results. of course i flush mine every 15k to 20k. i know that is way before the system needs it but i also have never had problems with a cooling system failure in any of my vehicles.

 

To flush all the old out of mine I just remove the radiator cap, use a stick to make the truck idle high (around 1200 or so), and remove the upper radiator hose at the radiator. Stick the garden hose in the radiator inlet and set the flow low to medium. The t-stat will cycle several times and in about 15-20 minutes the water coming out of the upper radiator hose will be clean.

Some radiator flushes state to empty all the old coolant mix out, fill with water and the flush, and drive normal for 3-6 hours. I have done this and just accumulated my time over 2-3 days. So long as your night time temps aren't low enough to freeze your cooling system and cause damage I think it is fine to leave the flush in there and drive it around, even like I did for 2-3 days. Just follow the flush manufacturer's directions. Some flushes may be more aggressive and must not be left in there, but it should state in the directions. I've always done my flushes in the summer, so freeze worries weren't a concern.

Waylan

 

Good ideas. I'm heading out to pick up some Prestone Super Radiator Cleaner. It's supposed to be stronger than the Super Flush. Now freezing may be a concern at night... It gets down to about 29 F at night. I guess I'll go ahead and flush it and try to drive it as much as I can today so I can finish it up by tonight. I can always flush it again later. It says to drive for 3-6 hours.

 

If you want to leave it in for a couple nights plug in the block heater........it heats the coolant and no real risk of freezing at 29F even w/o the block heater unless for several days.

Waylan

 

Cool thanks. I didn't get to it today because it's been raining and I've been busy. I hope the water that's remaining in the cooling system right now doesn't rust further.

I put a rubber glove over the opening of the water pump to keep out air. Hope that's enough.

 

Well I went ahead and flushed the system with the Prestone Radiator Cleaner, rinsed it out a couple times, and re-filled the cooling system with fresh Fleet-Charge antifreeze. As I had predicted, the radiator cleaner didn't really do anything. Just a little bit of difference. The water was all rusty colored when it came out but the radiator is still pretty nasty on the inside. Ten years of neglect can't be fixed with two bottles of cleaner. Maybe if I repeat this procedure every 2 years from now on it will eventually make a difference.

 

Just ready to do this myself....this post was a great help on flushing....

 

Did you change the thermostat as well. The chemicals in the flush could possibly melt the rubber ring or the bonding material that holds it on.

 

Glad it was a help.

No I didn't. Honestly the flush didn't really do squat. I'm not going to use it anymore. I heard you can damage your heater core, which seems like a pita to change out on these trucks. I'm just glad that I didn't run the flush for too long and I think it gets too dilute since these rigs have such a big cooling system.

 

By the way, while you change your coolant, mind letting me know if your water pump hole looked like mine? Did yours have a film of orange residue on it?

 

Years ago I had real good results with Duponts 2-part radiator flush,it has an acid that really cleans,then you flush it out & put in the nuetralizer,then drain that & filll w/antifrezze.
It cured alot of overheating vehicles @ the gas station I worked at.

 

I'm not sure what the formula for these radiator flush chemcials is.. Mercedes keeps it simple- use Citric Acid. You can buy it at a cake supply place and add about 0.5-1 lb/gallon I think. I got a 5 gallon pail about 10 years ago and still have lots left.
Run it hot and then rinse it all out. You'll find it quite effective at removing the corrosion and it's ussually cheap$$$. I think the comercial ones are mild as they don't want to be blamed for a leak forming(by removing the corrosion).

Michael

 

That makes sense. I have a 10,000 gallon inside swimming pool that i was having a rust problem with whenever i "topped" it off with our garden hose as we have very high iron content in our water.
after trying 17 million four hundred and seven dollars worth of commercial swimming pool chemicals especially made for this purpose, i happened on a pail of citric acid. Voom !! one cup per 10,000 gallons of water and rust is a thing of the past.

 

my coolant still looks like new with 138,000 miles on the truck-----it checks good to 35 below------is there a real reason to change it ?