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Draft—DEX-COOL 2007, Part 1: Revising A Less-Than-Accurate Report
by John R. Hess with additions from Mole Snoopster
To appear in March 2007 Cool Profit$ Magazine
© 2007 All Rights Reserved
Back in early 2001 (within Cool Profit$ Magazine #41), I first detailed specific DEX-COOL® contamination problems as part of a review of a presentation at the MACS 2001 Convention. The presenters were from General Motors and Equilon. (The latter, GM’s supplier of DEX, after a stint as ChevronTexaco, is now Chevron Corporation.) Within the first two paragraphs of that piece, I praised the two companies for their candor. I believe I even described their session as refreshing.

In my third paragraph, I carried more corporate water by pointing out that only specific vehicle models had contamination problems. Doing so nicely highlighted their argument that DEX, therefore, could not be the contaminating culprit: If DEX was bad, ALL vehicles using it should have suffered uniformly. Okay, well now I’m taking a lot of it back; please modify the title of the article in your magazine. Instead of MACS 2001: GM and Texaco “Bare All” about DEX-COOL®, change the “Bare All” to “Bare Little.” It could also say “Hide A Lot” or “Ignore The Obvious.”

Above: Rusty coolant leaks can be easily traced from the left coolant port of the IMG (Intake Manifold Gasket) into the center of the GM 3.1L/3.4L V-6 engine.

But that still leaves the logical question: if DEX isn’t the problem, why are all of those DEX charged vehicles coming to your shop with fouled cooling systems? Are the owners doing something so wrong to cause that amount of contamination? The clear answer in 2007 is: it’s probably not their fault.

Above: The same rusty coolant as seen above but when it's covered by engine components and still very difficult to see. (Especially by the vehicle owner.)


Back in #41 again, I described the GM Service Know-How video, Understanding Radiator Cap and Cooling System Contamination Issues, as a “must see.” I actually said: “Without this information, your cooling system service knowledge of late model GM vehicles is severely limited. Seriously!”

Well, yes, that 's true. However, if GM had originally installed the proper overflow tank in the correct location, and dittos for the pressure cap, plus properly designed intake manifold gaskets, maybe so many GM cars and trucks wouldn’t have become contaminated. I’d continue on that line but I’m getting ahead of myself, more on the video later.
4.3L: Hard to tell what type of radiator cap it is, but it and the fill tank are filled with rust and sludge.
Above: 4.3L V6. It's hard to tell which type of radiator cap it is, but it and the radiator fill tank are loaded with rust and sludge.

Next, as a description of the presenter's personal observations, I wrote that they advised to now start filling the overflow bottle of affected GM S-10 Blazer series vehicles to the Hot level. I would hope that at the factory, important factors like that would be more thoroughly tested. While I didn’t respond to it then, I will now. Fill it to Hot because filling it to the Cold level doesn’t keep enough coolant in the system. How come? (Not an intelligent question, but effective.)

Now here’s the real killer in that piece: “The coolant problems found in this survey were caused by system contamination, and not due to the breakdown of DEX-COOL.” Wait a minute, am I wrong or does that sentence conjure up the makings of a Johnny Carson-Jack Web “Copper Clappers” routine? Better yet, it could be a new, technically revised version of Abbott & Costello’s classic burlesque skit, “Who's On First?”:

Lou Costello: “If the contamination wasn’t due to the breakdown of DEX, where did the contaminants come from?”

Bud Abbott: “Well, see, the iron oxide (rust) component, it came from the upper engine block and heads. When the coolant level dropped too low, they became uncovered "beachheads," then overheated and rusted.”

Lou Costello: “Why did the coolant level drop?”

Bud Abbott: “For some vehicles, when the contamination blocked the pressure cap from sealing properly, the cooling system was less than properly pressurized. The coolant then evaporated at a lower temperature. The plugged cap also restricted the cooling coolant from returning to the radiator. (And the overflow reservoir may have overflowed too. It should have been a little larger, or mounted higher, or both.)

For other vehicles, when the intake manifold gasket failed it allowed coolant from a coolant channel to get sucked into an intake port.”


Lou Costello: “All that contamination came from rust only?"

Bud Abbott: “Some of the inhibitors themselves probably "dropped out of solution." Since the acidic inhibitors in DEX seemed to have caused the lower intake manifold gaskets to swell and crack, maybe some of the nylon degraded into the mix. Plus, some of the inner rubber hoses were seen severely gelled or cracked and degraded.”

Lou Costello: “But look, if the coolant level got low, how did the contamination get up high enough to plug the radiator cap.”

Bud Abbott: “Well, different from “green” coolant where contaminants sink to the bottom, in DEX they tend to float to the top. And maybe the wrong cap was chosen for the job.”

Lou Costello: “But if the coolant level was low in the radiator, I still want to know how the contaminants got high enough up in the system to foul the cap?”

Bud Abbott: “Maybe some of the contamination floated to the top before the coolant level started to drop. It could have been that when the car was still new, within the first few miles, sealer pellet material (that didn’t get along with the new coolant chemistry) combined with the other contaminants and floated to the top. Again, the rubber radiator hose material could have “gelled up
,” mixed with the other contaminants, and helped plug up the cap too. We don’t know.”

Different from the performance of world-class entertainers, this bit will never make the Baseball Hall Of Fame in Cooperstown. It does however, illustrate what a lack of crucial information, or maybe even misdirection, can do to the accurate and complete solving of problems.

Moving further along in Issue #41, I willingly passed along the advice that everyone should change the existing caps over to the Stant “Drop Center,” Models 10230 or 11230. Why? Because those caps are not supposed to foul as easily. Too bad they didn’t do that before putting out a few million of them.

Note: We believe GM went through a radiator cap vendor changeover that coincided somewhat with the DEX changeover. It is possible that engineers could have tested the new cap for pressure and temperature opening and closing accuracy, life cycling, etc., without subjecting it to the severe contamination it would end up enduring. Of course, the first probably wasn't checked to that level of fouling either.

About the 5.7L
On page 22, I restated what I was told, that CK Series 5.7L V-8’s had also suffered intake manifold gasket failures, but DEX was never found to be the cause. Not found by who? Nevada's John Bell thinks differently; Click Here to find out why.

The last paragraph of that article reminds readers the Stant cap is the best for the ST Blazer, where the cap is mounted at an angle on a radiator tank. Back to initial testing, you'd think someone would have checked that a little better during testing? Oops, during testing they kept the system full to Hot. This kept the contaminants building up in the DEX which meant no “beachhead rusting” of heads and block, and no plugging of the cap. Okay, I've beat that angle to a bloody pulp; I'll back off now.  $$$

End of Part 1.
Click for DEX-COOL 2007, Part 2
Click for DEX-COOL 2007, Part 3
© 2007 All Rights Reserved

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