# gunk in radiator res



## 6.0goat (Sep 27, 2007)

Just bought an 06 GTO with only 8,300 miles on it. While checking the fluids, I opened the little yellow cap where the radiator resevoir is located. Pulled the stick out and was amazed to see orange clay looking gunk all over the dip stick....ugh! Took it to a radiator repaid shop and had the flush and put Dex Cool back in. Two questions, what could possibly cause the Dex Cool to break down so quick and how many go back to green coolant after the warranty is out?? I've been told by more than one mechanic that Dex Cool SUCKS.


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## GTO JUDGE (May 14, 2005)

6.0goat said:


> Just bought an 06 GTO with only 8,300 miles on it. While checking the fluids, I opened the little yellow cap where the radiator resevoir is located. Pulled the stick out and was amazed to see orange clay looking gunk all over the dip stick....ugh! Took it to a radiator repaid shop and had the flush and put Dex Cool back in. Two questions, what could possibly cause the Dex Cool to break down so quick and how many go back to green coolant after the warranty is out?? I've been told by more than one mechanic that Dex Cool SUCKS.


*I have gunk in mine. I am thinking it is a rust inhibitor. As I do some research on the Dex-Cool coolant, I am learning it is crap. http://www.sancarlosradiator.com/dex-cool.htm

I had gunk in mine from new, which leads me to believe it is a rust inhibitor, which the owner manual does not mention. It is stated in articles I am reading the DEX-COOL breaks down and gunks up. At 24 miles on a car and coolant installed at factory some 6 months before then, the coolant has not had time to break down. This leads me to believe an additive was installed to aid in corrosion prevention. I have read elsewhere an additive similar to bars leak was installed to prevent corrosion, aid in the lubrication of water pump parts, and plug any leaks a radiator my develop over time. This further leads me to believe the substance is supposed to be there. 

According to the manual:

Notice: Using coolant other than DEX-COOL may cause premature engine, heater core or radiator corrosion. In addition, the engine coolant may require changing sooner, at 30,000 miles or 24 months, whichever comes first. Any repairs would not be covered by your warranty. Always use DEX-COOL (silicone free) coolant in your vehicle.

The recommended flushing and replacement of this coolant is to be done at 150,00K miles. To read what radiator repair shops say disputes the factory recommendations and they advise getting rid of the DEX-COOL and replacing it with regular anti-freeze, which will void the factory warranty, and require sooner maintenance of every 24 moths.

Having read in the owners manual the notice, and recommendations, I personally would follow what GM requires. 

I am old school. This goes with engine oil. I have never used synthetics before purchasing this car. I will use synthetics because GM recommends it. I guess I will do the same with the coolant. *


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## 6.0goat (Sep 27, 2007)

Well, that makes me feel better...that it happened to someone else. Interestingly, the GM service dept tech had no idea what it was. He told me that the Dex Cool was breaking down. Another strange thing was that the coolant level in the res was at the bottom eyelit on the dip stick. 

I agree with you following GM recommendations. They spent months, years of development spent boocoo's of money to research what works best. Taking the word of a joe blow mechanic over GM research is like taking an herbal pill over the recommendation of your doctor. Quack science.

The first oil change on my car, the previous owner put Castrol syn 10w-30 in spite of the large oil cap that reads MOBIL 1 5w30. To make matters worse, it was exactly a quart low so I am assuming the oil change place put 5 quarts instead of 6. I am thinking it surely hasn't used a quart of oil in the time of an oil change.

The only thing I don't agree with GM and it's just my lack of faith is changing the oil approx. 3,000 miles instead of waiting for the oil change light to come on. What do you think??


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## GTO JUDGE (May 14, 2005)

6.0goat said:


> Well, that makes me feel better...that it happened to someone else. Interestingly, the GM service dept tech had no idea what it was. He told me that the Dex Cool was breaking down. Another strange thing was that the coolant level in the res was at the bottom eyelit on the dip stick.
> 
> I agree with you following GM recommendations. They spent months, years of development spent boocoo's of money to research what works best. Taking the word of a joe blow mechanic over GM research is like taking an herbal pill over the recommendation of your doctor. Quack science.
> 
> ...


*The previous owner probably figured he was getting rid of the car and didn't bother to spend the extra $$ on oil. Many cars take 4.5 to 5 qts of oil to fill so instead of looking at the proper quantity they assume, or they go to places like Valvoline and pay the cheap cost of an oil change that only includes up to 5 quarts. 

As far as the oil change light. You are to go by the change indicator to change the oil. It is not measured on miles driven but engine revolutions. The computer monitors this and is supposed to let you know when to change it. Usually about 7500 miles give or take. I change mine out at 5K regardless. 3K miles oil changes is old anymore. With new engine technology and advancements in oils, changing out at 3k anymore is premature especially with synthetics. Owner manuals will reflect this, so reading it and going by what is stated in there about it will save ya money. 

As many have stated on here, they are finding many techs don't know as much as they should know about these cars. This is scary. 

As far as the coolant issue: At factory GM installs pellets in the radiator basically to lubricate internal parts, stop up any potential leaks, and it helps with rust prevention. Residue from this ends up in the reservoir and cling to the dip stick. People panic and think the coolant is breaking down. You can flush it out but as stated it is installed for a reason. *


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## 6.0goat (Sep 27, 2007)

That all makes sense. However, my thoughts regarding the oil is that it isn't a matter of the oil breaking down at 3K miles but a matter of what's floating around in the oil. What about just changing the filter at 3K?


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## bondosGTO (Sep 5, 2007)

also the computer monitors dirty, tempratures (water, air), drive habits etc. etc. and then tell you when to change the oil. 
the ONLY one that touches my car, to work on, besides my muffler shop, been doing business, for longer than i have been driving (parents use them) tranny shop for shifter, same story. every thing else is GM. might be more expensive, but peace of mind, and extended warrenty, mine dealer gave us an extened, extend warrenty, went and extra 5K miles when the front diffent out on a burban. also amsoil says, and backs up, oil changes every 20,000 miles when using there oil and filter. all they do is an oil test with your old oil. i never done it, a friend of mine with his old mitsu eclipse turbo, used synthetic from the factory (same weight), carquest filter (wix) has over 220K.


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## GTO JUDGE (May 14, 2005)

6.0goat said:


> That all makes sense. However, my thoughts regarding the oil is that it isn't a matter of the oil breaking down at 3K miles but a matter of what's floating around in the oil. What about just changing the filter at 3K?


*Some of the better oil filters, Mobil 1, K&N boast ultra filtration. I use either or.

Floating around? During the break in process some bits of metal shavings from new gearing will flake off. This is why an oil change after a few thousand miles is recommended. After that, you may get some but it's generally negligible. Dirt is the main concern. 

If using cheap oil filters maybe changing just that out I suppose would work, but the better ones.... I'd let them do their job until a full oil change.

If just changing out the filter, I'd keep an eye on the oil level, and replace as needed. 

You would be just fine going 5K between oil changes. If you want to change out at 3K then I'd do the entire change.*


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