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sludge in coolant



i dont know what happens if u mix these together.prob not good lol but my point is the gm manual is very mis leading for people who dont know anything about cars.we know to change our coolant before 100000 miles or were gonna have big problems but other people dont know that.gm needs to change that to every 25000 miles to prevent cortly repairs or go back to the green and it would not matter. thers a good article on the different chemicals in green and dex cool.it explains why dexcool gets so corrosive so quick because of thr different chemicals dex cool has.ill try to find it and post it on here.
 
I'm sure my car was on the original coolant when I bought it with 91k in 2008 but I had the dexcool eat through my coolant block plate right behind the flywheel along with the LIM gaskets about a year ago , that was a *****. I had the coolant flushed twice in the year I had it before this happened trying to get rid of the sludge but it led to no success. I'm on the green now and have had no problems with it. To eat his own though.
 
rampage said:
thers a good article on the different chemicals in green and dex cool.it explains why dexcool gets so corrosive so quick because of thr different chemicals dex cool has.ill try to find it and post it on here.
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Do this... I haven't seen any evidence that Dex-Cool is corrosive in a well-maintained vehicle. Then again, I haven't looked for it or tested my own (I'm no chemist).
 


I got the intake gaskets replaced on my 02 GP....it wasn't leaking but i wanted it done when i heard the 3.8s had some issues with the plastic gaskets...it was showing some sludge around the rad cap..i think Gm was paying a bit if the dealer did it but @85.00 \hr rate....I got a GM mechanic that does my work for me and he did put the dexcool back in it...said never use green or yellow coolant in the gm cars...just waiting for him to do my monte ss
 
yeah, all GM techs will say that...

Even though 3800's with the a similar LIM gasket were factory fill ethylene glycol...
 
I remember once upon a time in 2005 when I first got my 1988 Jeep Cherokee it had a water pump leak. I removed the thermo housing, and the water pump, stuck a hose in there and turned it on. Guess what came out? Green sludge chunks. The engine had never been flushed, only had coolant drained and filled a few times.

Then I suffered from weak heat for a few winters, only to remove the heater core and find this... yep a broken and sludge filled heater core from green coolant.


DSC01245-1.jpg


Moral of the story, any coolant sitting in an engine long enough with air exposed to the coolant will eventually gel up, not just dex. In the 3800 case, either plastic elbows start leaking, or the LIM gaskets start to crack due to heat cycles and break on the molding lines around the coolant passages, letting in air. Let that go long enough and you have sludged red coolant.

Last spring I drained the dex in my engine and it came out clean, with leaking LIM gaskets and all. On top of that, the car had been sitting in one spot since 2006. Changed my LIM gaskets with L32 aluminums from the Chevy dealer, popped in 2 new elbows, and replaced with fresh dex. Like others have said, if there is no air in the system (any system for that matter) there wont be sludging. And if there is no air exposed to the system, you need to change the coolant every 2 years or so, or it will turn old and acidic.
 
You can check the corrosion resistance of your coolant with a dmm. Set it to voltage and place the positive lead in the coolant in the rad and the neg lead to ground. You do not want to see a voltage over .3v. The coolant when it gets old starts to work like the electrolyte fluid in a battery and our engines have dissimilar metals in them. So that turns it into a battery and starts to produce a voltage.
 
If it was rust , and not just the dex-cool , then why is mine that nasty color and is also sludge . I have an 07 GXP and the 5.3 ls3 is all aluminum. It is put up tor the winter but when spring gets here I will flush it out and replace it with green.
 


If those were rusting to the point that they create that kind of mess in the cooling system , then I would have bigger problems don't u think ...
 
I have a 2006 Grand Prix GT with less than 90,000 miles and I am having the sludge in my coolant. Also, I have no mechanical ability at all so I am dependent on my mechanic, who has worked on our cars for years. The car's temperature gauge started redlining about a year ago and he did some basic work to fix it. This past summer it would do the same when I was stopped at a light. The car would give me a message that the AC was shut down to protect the engine. Once I started moving it would drop in temperature. He flushed all kinds of things and even put in a new radiator. The past month (cold ass temps) it started doing it again. He has flushed everything, checked the heater core, replaced the thermostat and replaced dexcool with the green stuff. This was just done two weeks ago and it is acting up again. I can tell because the heat blows cold air if I am stopped at a light and gets warm when I am moving. I pulled the rad cap off this afternoon and the sludge has returned. Any ideas?

He is even at a loss and has been calling in favors from other mechanics trying to figure out what is wrong. I hate to dump the car as it does not have that many miles, but I am not going to keep pouring money into it every few months.

Edit: I bought the car certified used from a GM dealership about 6 years ago. It had about 10,000 miles on it at that time. My mechanic said that dealership is known for putting Stop-Leak in their vehicles. He thought this might be causing the sludge buildup initially.
 
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A poor flush when switching from dex to another coolant type will cause sludge. Any residual dexcool will raise hell in there.

Sludge may be caused by a leak in the cooling system. Is anything dripping? Are your coolant elbows near the radiator intact? Is coolant disappearing? Is coolant being burned by the engine - indicated by a sweet smell in the exhaust?

How's the oil? Is it full? Over-full? Healthy? Milky?
 


SlowNA06 said:
A poor flush when switching from dex to another coolant type will cause sludge. Any residual dexcool will raise hell in there.

Sludge may be caused by a leak in the cooling system. Is anything dripping? Are your coolant elbows near the radiator intact? Is coolant disappearing? Is coolant being burned by the engine - indicated by a sweet smell in the exhaust?

How's the oil? Is it full? Over-full? Healthy? Milky?
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We were both shocked when the sludge returned after putting in a new radiator. This was done about 5 months ago (right before winter really started here) and it was fine until about 6 weeks ago. I have not noticed a smell with the exhaust. The oil was a bit low when I took it in a couple of weeks ago, but it was at 3 months and 3000 miles since the last oil change. They have not commented about a strange color with the oil.
 
SlowNA06 said:
If there's no rainbow in the coolant from oil, I'd guess it's not oil getting in; just air.
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From reading earlier in the thread it looks like it could be a LIM repair/replacement job. Any idea what that would cost for a 2006 GT? I would need a mechanic to do it.

Thanks for all the help!
 
$600-800, if I recall correctly. Depends on the mechanic and area.

Typically, a 2006 should not have this issue since it has the updated aluminum gaskets, but since you've overheated the car, I suppose they might cause an issue. As such, head gasket failures are particularly rare on the 3800, so I'd suspect the LIM gasket first as well.
 
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