Was told bt a GM mechanic that one thing that keeps her busy with head gasket repairs iis people who insist on adding regular coolant to Dexcool. Also, not runnning enough water with Dexcool.
ok4450,
A cars cooling system is supposed to be a closed loop system. In a closed loop system the fluid that is first put in may have some oxygen. That oxygen may attack the surfaces within the closed loop until all the oxygen is used up. At that point the fluid will be de oxygenated, and no further corrosion will take place if there is no means of new oxygen to enter.
I suspect those cars that go several years beyond there recommended antifreeze change, and the coolant still looks perfect is because that car by chance had a tight system.
I suspect car antifreeze has additive to naturalize oxygen up to a point until the additive is all used up. At which point everything brakes down and corrodes into a big mess.
As for pressurized reservoir bottles that act as expansion tanks. You don’t have to look any farther then a 3rd generation Taurus to know what a disaster that was. That system turned the coolant into brown mud, and that was with normal green antifreeze.
I cringe at any car that uses a pressurized reservoir setup, because there are to many possibilities for the system to breath, especially through the PSI cap on the resivoir bottle.
So in theory if a car manufacture produced a true closed loop cooling system. That being a reservoir/expansion tank with a air bladder (not a air gap), air tight clamps, hoses, intake manifold gaskets, and radiator. The antifreeze would be just that, and would last a life of the car. No Oxygen no corrosion.
Have a 2002 Silverado, not head gasket problem that I can see, yet I am pouring coolant in more than I have in any other vehicle I have owned (1st Dex-cool). No puddles to be found around truck. Also just had tune up done fall of '07, Fuel injector system replaced '08, and now, not even 40,000, replaced cap,rotor, and plug wires. Plugs are fine. Any idea?
As stated previously
"It seems from my reviews that a bad radiator cap can cause the problem, It is not air and fluid but air, fluid, and engine heat."
Sounds like an manifold intake gasket leak. My mechanic found a little coolant in the oil of my 2000 Blazer after draining it and that was his diagnosis. The dealer confirmed it and did the repair. The only symptom was a slow drop of the coolant level in the reservoir. There were no visible leaks or puddles.
Ed B.
Since GM refuses to stop using DexCool, perhaps it would be good to simply take a new GM vehicle and get rid of the DexCool and replace with green antifreeze after a thorough flushing. The other coolants are supposed to meet warranty requirements.
GM is so very slow at correcting problems.
DexCool is not related to headgasket failure,it is related to upper and lower intake manifold gasket failure and sludging the cooling system.
The intake manifold gasket leak is plain, and simply caused by a bad designed gasket that has nothing to do with dex cool anti freeze.
However, it does cause sludging issues. Green coolant does not, even if the radiator cap is not airtight.
Thanks to you for a little sense of relief, we have had 1 page of comments because I forgot a comma, and 1 page attacking my best guess, I don’t really care as I have gone universal, and am willing to hear any other exlpanations, but this has gone on 2 pages long for nothing and would think it is time for it to fade away.
My 2000 Impala LS 3800 engine with 102,000 miles still running Dexcool with no coolant issues. It has had two coolant changes sense new.
Sure I had over 100k with dex cool and no problem, we are not talking about those with no problem. aargh
You are likely fortunate enough to have a system that is airtight and stays topped off via the overflow bottle which you no doubt maintain between the min and max lines. Even GM has stated that a system that doesn’t stay topped off is more likely to sludge…kinda putting it off on the consumer for poor maintenance. Even though that is probably true, GM should switch to a different coolant that is more tolerant of poor maintenance which is probably more widespread than the automakers think. They apparently don’t try to idiot proof their systems as much as they should.
I don’t think anyone gets my point yet.
The system in many GM cars uses 2 styles of plastic tanks. One a simple overflow tank and the other a pressurized one.
On the pressurized ones some air is normal and MUST be in place. The tank is designed to have an airspace in it. Every time that cap is loosened or releases, fresh air will be admitted.
Coolant composition and heat could be at fault but I don’t see air being an issue at all. As I type this I’m at my son’s house in CO. Bringing up this discussion caused my son to mention that there was half a jug of Dex Cool in the garage. It was sitting there when he moved in several years ago and remains unused.
Not one iota of sludge in it.
These pressurized tanks are nothing rare either. They’re used on many types of vehicles and have been for many decades. SAAB, Ford, Lincoln (my Mark has one), Corvette, etc, etc, etc. My 83 SAAB Turbo even has one.
And I agree with Americar; DC is not behind the gasket failures. Crummy design. It would be a great design except for that annoying habit of rubber not maintaining its shape and elasticity.
I understand your point exactly. The simple overflow tank will put water in the overflow tank if the system builds up too much PSI, and siphon it from the tank back into the system when the system cools down, and goes into a vacuum.
The pressurized tank is a expansion tank because the air gap in the tank will allow for expansion and contraction of the coolant because a gas can be compressed and liquid cannot. What I think you may not understand is the fact that the air gap in the expansion tank only has a small percentage of oxygen (the air we breath is only a small percentage of oxygen). The oxygen in the expansion tank air gap will eventually get used up. Then there will most likely only be nitrogen and other inert gasses left in the reservoir tank if the system is totally air tight.
My suggestion is not to open the cap on the pressurized reservoir tank unnecessary because it will allow oxygen back into the system.
This system will work perfectly if 100% air tight. The problem is if it becomes not air tight.
Since she is an excellent mechanic I’ll stick with what she said.
ok4450,
Her is another thought. Fish will die in a fish tank if the air pump is turned off do to lack of oxygen even thou the top of the tank is NOT sealed. The water pump in a automobile makes a great agitator to mix oxygen into water if air can gets in.
I hear what you are saying, but you are singing to a crowd that is not listening.
You need oxygen to survive, if you didn’t you could live forever. That was quote from one of my teachers a long time ago
This UIM/LIM job cost me $1800 and of course I cannot find the paperwork for the job done 2 years ago . BTW the transmission in that car had to be rebuilt at 42K miles even with PM at 25K miles . No more big 3 vehicles for me except for the 3/4-1 ton diesel trucks I need for work . I really like my Honda and Toyota .