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Dex-Cool Sludge: RIP, Radiator. Green vs. Orange

33K views 67 replies 25 participants last post by  BuckyBoy02 
#1 ·
Dex-Cool sludge contaminated the cooling system of my Bravada ever since I purchased it. For the previous owner, it wiped out a heater core and intake manifold gasket. For me, it took out a water pump (if Dex-Cool was the cause) and, more recently, a radiator.

I purchased the rad from PartsTrain, one of those identical-to-50-other-parts-websites websites. It's an OEM Delphi shipped for $131.50. Mind you, my truck has the oil cooler/tranny cooler too.

I purchased the GM PN: 12346500 (Heavy Duty Cooling System Cleaner) which is mentioned in the Dex-Cool GM TSB. I was planning on using it, but then the rad sprang a leak in the plastic end tank, and looking at the amount of rust in the rad, I wasn't going to just replace the end tank and call it fixed.

My question is, should I use the cleaner (and do the 2.5 hour cleaning procedure) or at least flush/backflush with just water BEFORE I install the new radiator, or do it AFTER I install it.

My concern is that when I install the new radiator, I don't want any of the remaining crud in the hoses, heater core, block, etc. to travel right to the new radiator.

Which would you do? Is there any reason for my concern? Also, would you put regular green antifreeze back in after a thorough flush, or stick to GM Dex-Cool?
 
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#2 ·
I'd be careful with the cleaner but a good flush would not hurt. As far as the Dex-Cool chuck that crap in the trash and either run green or HD purple. The purple and green work great and don't chunk up like the dex-cool
 
#3 ·
First, flush out the system (the old radiator) with just water a few times and then with the Prestone-type flush cleaner stuff. Use the Prestone flush kit, with the tee that goes into the heater core hose connected to the garden hose.

Also open up the lower drain on the radiator tank while flushing. Close it for a while. Then open and drain again.

Flush it in cycles, get 'er real hot. Let 'er cool down some. Then flush it out again and again. It should not matter if the tank leaks while you flush it out.

Only then would I install the new radiator. Then do the 2 1/2 hr GM flush.

Just my $0.02
 
#5 · (Edited)
Great, thanks for the tips.

WalkGood, that's what I originally assumed I should do, I'd hate to get more sludge in the new radiator if I can prevent it. Just the look of it frightens me...



^That's what it looked like when I bought the truck... I flushed it out (only with prestone, though) and it was fine for a few months, then the sludge was back. I hope I can get rid of it once and for all.

And I guess that's a big NO to Dex-Cool!

Nick
 
#7 ·
I feel your pain, although mine was not dexcool related, just neglected. I just finished flushing mine about 10+ times over 2 days using Prestone and then better results using dish soap before I got clean water
 
#8 ·
Intersting... Dish soap?

I tried finding information on "flushing without a radiator" but google gave me nothing...

According to GM, with their "acid in a bottle" cleaner, as long as fluid can pass through the 3rd tube from the top in the radiator, it will clean all of the junk out in one flush. (Mind you, the flush involves running the engine at 1800rpm for 2.5 hours with the AC on. I couldn't see how much of anything could survive that treatment)

Nick
 
#9 · (Edited)
I actually use the dish soap trick alot. My buddy was a former vw tech and they used it alot at the dealership. It does wonders, It foams up when you run it the first time at idle, then drain refill and run and drain until the water is clean...Usually a few times.... Probably wouldnt work as well in your situation trying to flush without a rad, I had sludge floating in my rad and the soap did the trick, Plus its easy, just time consuming..but its all at idle for 10-15 mins at a time, then drain then repeat
 
#10 ·
IF you are gonna use dish soap JOY is the only way to go. Since machine shops and back yard mechanics use it since it will strip oil and other contaminants off a block.
 
#11 ·
I was just looking into doing a cooling flush using Prestone stuff too, I was concerned about connecting the house water line up to the system though, I think it is like 50 lbs pressure ... if I leave the bottom open and maybe don't turn the faucet on more than a bit would that be likely to not harm anything?

Mine was low on collant when I bought it, the old red dexcool, and has some white crusty stuff around the rad cap, no leaks though and lots of heat thru the heater.

Thanks
 
#23 ·
I was concerned about connecting the house water line up to the system though, I think it is like 50 lbs pressure ...
You won't hurt anything with the hose connected to the Prestone flush tee. You do NOT close the radiator cap. No harmful pressure will build up. You do use the elbow piece in the raditor cap neck opening to direct the water away from the engine bay.
 
#12 ·
I think there is a ton of buildup inside of the block. Anyone whos ever done intake manifold gaskets can attest to this. And I don't think any sort of dish soap is going to take that build up out of there.

As far as I know, the routine for the GM dealerships is to use a certain acid that reacts with the buildup and eats it away. As said before, the car is ran at a certain rpm for a couple hours and it's ususally good to go.
 
#13 ·
I think there is a ton of buildup inside of the block. Anyone whos ever done intake manifold gaskets can attest to this. And I don't think any sort of dish soap is going to take that build up out of there.

As far as I know, the routine for the GM dealerships is to use a certain acid that reacts with the buildup and eats it away. As said before, the car is ran at a certain rpm for a couple hours and it's ususally good to go.
agreed. its not just the radiator that looks like that,
its the entire system. and you'll see debris in you new radiator
in no time, even after conventional flushes.

the GM flush might be the best solution BEFORE the radiator swap.
 
#15 ·
from what i've read, the GM 12346500 cleaner is really good stuff.
far more effective than the typical liquid "cleaners" sold by most stores...

Prestone makes it, and used to market it as "AS100" heavy duty
cooling system cleaner, but no longer sell it through
their own name.
 
#16 ·
But, According to the TSB, 12346500 is a 2-part acid/neutralizer powder. When I went to pick it up at the dealer, the parts guy said that it was replaced. Now, they use a 16oz bottle labeled "GM VehicleCare Heavy Duty Cooling System Cleaner", GM PN: 88861344.

The instructions on the back of the bottle tell you to run the liquid in the engine with water "at a fast idle for 40 minutes to an hour." I don't know if I should follow the TSB or the directions on the bottle. I don't want to do damage to all of the metal parts the cleaner touches...

Nick
 
#18 · (Edited)
i just called my local dealer as you were posting that.
they also confirmed the new part# you mentioned,
and that the powder formula is no longer available.
i wonder if this new stuff is the same as the liquid
cooling system cleaner sold by Prestone?

i would follow the bottle directions, not the ones
from the old TSB...

from what i gather, the old stuff was basically
oxalic acid, AKA: wood bleach. sold at most hardware
stores. the "neutralizer" is supposedly just baking soda...
 
#19 ·
On the New Part Number, the contents are:

Phosphoric Acid and Citric Acid

The MSDS Number is 1185487, if that would be of any help.

Nick
 
#20 · (Edited)
yeah, on the Prestone Radiator "Cleaner" it says "non-acid formula",
but their Radiator "Flush" doesnt say on their site what it contains...

i might just go get the GM stuff. my cooling was gunked up some before
i bought it. SEVERAL thorugh flushes later, there are traces of
it still in there...
 
#21 ·
I remember talking with my auto teacher a couple of years back, and he was telling me about his son's Chevy Malibu that used Dexcool. He thoroughly flushed it with regular, diluted cleaners 4 times, and there were still traces of rust in the coolant... I think this GM cleaner is the way to go. I hear nothing but good things about it.

Nick
 
#22 ·
went to the local parts store and looked at both of the
Prestone flush/cleaner products. they both use
sodium citrate as their active ingredient.

let us know how the GM stuff works for you..
 
#24 ·
Tomorrow, I'm going to be:

-Flushing the system with water and some regualr flushing liquid if I have it
-Installing the new Delphi radiator (took one day to get here!)
-Cleaning the Recovery Tank with OxiClean (supposedly the best thing to get rid of the DexCool film in the plastic tank...)
-Flushing the system with GM Heavy Duty Cooling System Cleaner (In Liquid Form)

I'll post back with the results.

Nick
 
#26 ·
I'm not sure how many rows, but I do know that it is the exact same thing that came out of the truck (Delphi Brand). Also, since GM banished drain plugs a few years back, the drain hole is plugged permanently.

Price was $130, Free shipping, it arrived in 1 day. (Shipped from Mass)

Nick
 
#27 ·
i just picked up a bottle of the GM cleaner today.
i may try to get around to flushing the system (again)
with this stuff this weekend.
 
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