intake gaskets

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sjay

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Why are chevys having such big problems with their intake manifold gaskets?my99 malibu,my friend's 94 lumina and 2000 cavalier and brother's 2002 impala have all had to have the gaskets replaced.
 

Paul

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My opinion is thats its the Dexcool coolant.One can't leave that stuff in a cooling system for as long as Gm says or the maker of Dexcool claim.Then again I flushed a cooling system on a 96 Lumina 3.1L a few weeks ago,it had the original Dexcool coolant,and the gaskets were fine,no signs of any leaks.
 

Jim Davis

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my $.02, like Paul said its the dexcool, but I dont think the dexcool takes too well to being topped off with other coolants. again, just my opinion.
 

MikeM

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I too agree with Paul. I also have a more radical opinion, in which that stuff should be removed and flushed out right away and real anti-frz installed. But that is strictly my opinion. And many here will disagree. In which I respect their opinions strongly.
 

autodr

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The intake gaskets on that vehicle are a series of rubber o-rings molded into a plastic carrier (nylon 6,6). The nylon carrier.. or frame.. of the gasket degrades causing the rubber o-rings to shift out of place and leak. The threshold point of when the nylon degrades is about 275 degrees. The normal operating temp of the engine is 195 to 225 degrees. However, when you shut the engine off, there is about a 1000 degrees worth of heat in the metal of the cylinders and head. That is transfered into the now standing water around those areas. That causes the water in those areas to rise over 275 degrees in places (that's why it is so important to have a 50/50 mix and a good rad cap of proper pressure rating, to keep that water from boiling after shut down).

If you only have the engine off for a short period of time... like stopping to refuel and firing back up again, the extra heated water is moved to the intake gaskets and causes a little damage to the gaskets. Over about 70 or 80-ish thousand miles... you are replacing the gaskets.

Dex-cool drops the ball when it comes to protecting the gaskets. Dex-cool has no silicates in it. It is pure Organic Acid Technology (O.A.T.) protection. OATs protect metal only. They do it in a similar way that gun bluing protects a gun barrel. They treat the metal. OATs don't treat plastic or rubber. Conventional green coolants protected everything the same, metal, rubber, plastic... by "painting" everything in a layer of sand. That's also largely has to do with why Chrysler (as well as imports) don't seen to have the same problem when they use OATs also... they don't use pure OATs. Instead, they use "hybrids". A Hybrid coolant uses some silicates (or nitrites for some formulas) to provide that "painted" on layer.

It's also been found that one of the OATs used in Dex-cool... 2CHA??? something like that.

So it's not just one thing. But it seems Dex-Cool plays a big role, possibly two of them.
 

civicduty

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I'd like to express my unprofessional opinion ;D that Dexcool is often left in there too long. GM gives a 5yr or 150,000mi life for it, but people seem to only go by the 150,000 miles! (Many people who buy new cars don't keep them that long.)

I seem to recall mechanics here on BAT advise: Change your Dexcool every 3yrs or 50,000mi and it should serve fine. Also don't let the coolant level get low to introduce air into the cooling system.

autodr, thanks for the great explanation of how the nylon degrades in the heat soak, and how the proper ratio of coolant/water is so important. Would an engine with an aluminum intake be fine with pure OAT?

I'd like to ask how the silicates would protect the plastic from heat..?
 

autodr

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civicduty said:
I'd like to express my unprofessional opinion ;D that Dexcool is often left in there too long. GM gives a 5yr or 150,000mi life for it, but people seem to only go by the 150,000 miles! (Many people who buy new cars don't keep them that long.)

I seem to recall mechanics here on BAT advise: Change your Dexcool every 3yrs or 50,000mi and it should serve fine. Also don't let the coolant level get low to introduce air into the cooling system.

autodr, thanks for the great explanation of how the nylon degrades in the heat soak, and how the proper ratio of coolant/water is so important. Would an engine with an aluminum intake be fine with pure OAT?

I'd like to ask how the silicates would protect the plastic from heat..?
Actually, if you read the back of a bottle of A/C Delco brand dex-cool.... you'll be in for a surprise!

The intakes are aluminum and so are the rads of vehicles that the factory puts dex-cool in.




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civicduty

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autodr, that is something to read 2 years / 30,000 miles on the bottle! No wonder many GM vehicles end up with muddied up cooling systems. Last GM I owned was a 1986, and it got conventional green. It's radiator failed while I owned it but the rest of the cooling system was fine. It was a LeSabre with the special "high output" 3.0L that had rather low output for the vehicle weight. ;) But it was a very comfy car, especially for passengers.

Isn't 2yrs/30k miles the same as the old high silicate formula interval? I am quite sure the last GM cooling system I looked at (a 1997 Century) had 5yrs/150k written on it, but I could always be wrong!
 

autodr

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civicduty said:
Isn't 2yrs/30k miles the same as the old high silicate formula interval? I am quite sure the last GM cooling system I looked at (a 1997 Century) had 5yrs/150k written on it, but I could always be wrong!
Yep.... the 5yr/150k stuff is Texaco's idea. They invented that stuff. GM started using it. I understand it because of credits that the EPA issues for things that exceed emission's standards on a 100k mile time frame. Maint. is emissions also (that's why some engines have a 60k mile replacement interval for some states and the same engine will have 105k interval in Mass, Cali. and some others). When the manufacturer makes something that the EPA wants to fine them on, they can apply those credits from other issues toward the fine.

AC/Delco is the only one I've seen that doesn't push the 5/150 crap. They say 2/30. Its funny that they call it "extended life"... but then again, they are not the ones who started that "Dex-cool is extended life" BS. So by them saying "extended life... they don't have to mean that it IS extended life. They may say that as merely a way of identifying it to the reader as that type of coolant.
 
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