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#1605125 - 09/19/09 07:01 PM Rust buildup at Radiator Cap
raidermark Offline


Registered: 06/19/09
Posts: 49
Loc: Nevada,US
Under the radiator cap is a gunky rust buildup on my 2003 Chev Impala w/108K mi (original owner). I've done 3 Radiator back flushes w/ the Prestone back flush kit. The old Anti freeze always looks good & clear. I've changed the thermostat once. I've released the pressure on the bleed screw until fluid comes out although I don't really know what I'm doing with that. Is the rust at the radiator cap anything to be concerned about?
Also, does anyone really believe the new cars can go 100 K before the first Radiator flush? Thanks for any advice!
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1998 Suburban 1500
2014 Equinox
2007 Yukon XL 2500
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#1605134 - 09/19/09 07:20 PM Re: Rust buildup at Radiator Cap [Re: raidermark]
Boomer Offline


Registered: 09/19/08
Posts: 1814
Loc: Pennsylvania
Death Cool residue!
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2013 VW Passat TDI SE, 33,300 miles
2014 VW Jetta TDI SportWagen 18,055 miles

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#1605144 - 09/19/09 07:40 PM Re: Rust buildup at Radiator Cap [Re: raidermark]
Warstud Offline


Registered: 09/02/05
Posts: 4024
Loc: MIchigan
I don't think it's anything to worry about since you've done 3 flushes to it already. I just hope you replaced the Dex-cool with something else though.

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#1605160 - 09/19/09 08:03 PM Re: Rust buildup at Radiator Cap [Re: Warstud]
defektes Offline


Registered: 09/09/09
Posts: 3216
Loc: Hesperia, CA, USA
I flush every 75k tune up. I have had many GM's and Dexcool isnt that bad.
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#1605166 - 09/19/09 08:08 PM Re: Rust buildup at Radiator Cap [Re: defektes]
Nick R Offline


Registered: 07/14/09
Posts: 11015
Loc: Albany, NY
Does that impala have the 3.1/3.4/3.8L v6? It could be that the dexcool has sludged/rusted your cooling system. It is especially bad in those engines because it eats away the plastic intake gaskets so you have anti-freeze getting into your engine. I would drain your oil and make sure there isn't any oil in it. You might have to do a UOA to find evidence of it in there, but you may be able to tell simply by looking at it.
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#1605484 - 09/20/09 05:24 AM Re: Rust buildup at Radiator Cap [Re: Nick R]
raidermark Offline


Registered: 06/19/09
Posts: 49
Loc: Nevada,US
I have the 3.8 L engine. I just changed the oil today. The old oil looked fine, nothing foamy & no water at all in the oil. I use Mobil 1 Extended & change 7500 mi. I've been using Prestone 50/50 pre-mix Red Anti freeze. I'm wondering if the rust at the radiator cap could be a condensation issue.
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1998 Suburban 1500
2014 Equinox
2007 Yukon XL 2500
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#1605510 - 09/20/09 06:58 AM Re: Rust buildup at Radiator Cap [Re: raidermark]
Boomer Offline


Registered: 09/19/08
Posts: 1814
Loc: Pennsylvania
In all seriousness, this residue is typical of Dex-Cool reacting with oxygen. The fact that you are seeing it around the cap indicates to me that you have a leaky radiator cap and air is slowly getting in. If you don't replace the cap or correct where the air is getting in, you will slowly sludge out the cooling system on your engine. Dex-Cool works OK UNDER A CERTAIN SET OF CONDITIONS but if your engine wanders outside of those, beware. And it does eat those gaskets out. Had this happen on my 1997 Chevy truck.
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2013 VW Passat TDI SE, 33,300 miles
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#1605758 - 09/20/09 01:02 PM Re: Rust buildup at Radiator Cap [Re: Boomer]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
I have run Dex Cool in at least 5 GM vehicles and 3 boats (5 engines) without any issues. On the boats however I do not flush the system but drain and replace 2-3 quarts of coolant each year. I also use prestone anti rust/anti corrosion additive in all as well. I have spoken with Prestone technical suport several times and they have advised me to stick with Dex-Cool versus changing.

One important note: use distilled water to mix your coolant to the 50-50 or get the pre mixed. Dex-Cool had an adverse reaction with some Gm intake gaskets but that was the gasket material and has since been fixed.

The anti- Dex-Cool hype on here is just that...hype. Millions of GM cars have run 100k on Dex-Cool with no issues. I have had 5 of them. Any coolant will react with a leaky radiator cap.
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#1606570 - 09/21/09 10:15 AM Re: Rust buildup at Radiator Cap [Re: Boomer]
raidermark Offline


Registered: 06/19/09
Posts: 49
Loc: Nevada,US
Thanks, I'll replace the radiator cap. That makes sense.
_________________________
1998 Suburban 1500
2014 Equinox
2007 Yukon XL 2500
Mobil 1

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