2007, Part 3a:
General Motors DEX-COOL Memos
by John R. Hess with
additions from Mole Snoopster
To appear in March 2007
© 2007 All Rights Reserved
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Class Action lawsuits
filed against General Motors have produced the expected ton of evidence.
Among that stack, however, are several internal, documents that appear
to be from GM's own Quality Control groups. For some reason, these
somewhat embarrassing papers not only ended up as evidence, but evidence
in the public domain.
help ameliorate the sliding confidence in DEX at the service shop and
technician level, GM began reaching out 2001 to auto service
organizations, like NARSA.
At meetings with cooling system technicians, they recommended specific
parts and procedures to help stem the tide of severe problems in certain
DEX-charged vehicles. Below are evidentiary quotes from behind the
scenes efforts that undoubtedly led to that outreach. Mole and I believe
them to be valuable to both cooling system service technicians and
vehicle owners. Much of misinterpretation and confusion about DEX
problems can be corrected by reading the contents of these documents.
They are in no particular date order.
From a March 2000 meeting presentation titled:
Cooling System Corrosion S/T, and subtitle: Dex-Cool Field Action
Proposal, GM Brand Quality - Truck, 3-17-2000
Here's GM's own determination of "Contributing Causes":
" Root cause appears to be operation of the vehicle (usually
20,000 miles) with an underfilled (sic) cooling system.
An underfilled radiator leaves portions of the engine exposed to air
and coolant vapors on the cool down, therefore prone to corrosion.
S/T Plants (especially Moraine) had been underfilling systems. (JD
Power sufficiency plan item led to a PAD change on 8-31-99)
This action does no address prior customer concerns
Unlike green coolant, corrosion particles float and rise to the top
Radiator Cap design/durability is suspect
Radiator cap orientation promotes air entrapment and inhibits
Minimal capacity of the recovery system
High underhood temperature of S/T products
Little customer warning to condition
S/T products are a high lease demographic"
Cynicism at GM:
Apparently, from one of these meetings' presentations, a somewhat
cynical employee had prepared two slides comparing what Ford was just
going through with their Taurus-coolant debacle to what he/she didn't
want to see happen to GM in the next year or two.
"What We Don't Need
Automotive News 3-00 (March 2000)
"Ford throws cash as gasket"
Buys back damaged vehicles
Ford Taurus also had
"What We Don't Need
Automotive News 3-02 (March 2002)
GM Throws Cash at Dex-Cool
S/T Corrosion Issue Escalates
150,000 miles not feasible
Buybacks, Reimbursements increase
Back to Green Coolant"
This presentation panel pointed out some fairly strong customer
dissatisfaction. As "Regional Service Managers Input,"
it's coming from their own people!
" S/T Coolant Corrosion
is one of the major customer dissatisfiers (sic) currently in the field
Administration of expense varies due to lack of uniform direction
Service businesses and dealer loosing faith in Dex-Cool as a
One slide contains 3 bulleted thoughts on the financial burden DEX laid
on GM's Warranty Plan: two define the problem and one delivers a
"General Motors Protection Plan
Financial warranty staff request to allow payment for coolant flush
outside of the warranty period for vehicles with Dex-Cool.
Both MIC and the Financial staff did not forecast this expense in
their accruals and consequently they don't want to have it added to
their respective accounts.
My suggestion would be to expedite a customer satisfaction policy to
provide this service to all customers. That includes all customers,
provide the correct dealer and customer notification and clearly define
the coverage and procedure for the dealer."
Speaking of Customer Satisfaction Policy above, how about a $23.2M
"Proposed Action" to handle a Full Recall for just '98-'99 S/T
"1998-1999 S/T equipped with 4.3L Engine Preventative Worst Case:
Proposed Action: Issue Customer Satisfaction Recall now. Inspect for
full coolant, top off as required.
1998 = 421,146 Vehicles
1999 = 364,000 Vehicles (Est)
x $28.71 (0.2 hrs X 56.87 National Ave Labor
$22,541,541 Rate + 17.34 Cap and Coolant
19% Top Off Reqd:
x $4.35 Material
$22,541,541 Inspection Cost
648,924.30 Top Off Cost
Here's one from a June 29, 2000 Project Summary that explains rust in B
Model car cooling systems.
"Determine what's affecting other
models and why:
1996 Model B cars (Impala, Caprice, Roadmaster):
Coolant recovery bottles and system architecture were altered for the
1996 model year coincident with the introduction of DEX-COOL. Poor
design de-aeration bottle, location of coolant return line in the heads,
and a change to the de-aeration line design to increase heater
performance, all combine to create iron oxide contamination on the 1996
These models went out of production at the end of the 1996 model
Here they mention that all contamination is not the same in makeup, but
it's created by the same condition.
"Determine what's affecting other models and why:
W/U equipped with 3.1L/3.4L V6:
The 3.1L and 3.4L engine families that use a Sundram drop center cap
mounted at an angle, and a non-pressurized coolant recovery bottle (W
cars and U vans) also exhibit coolant contamination of the radiator cap
and radiator neck.
The makeup of the contaminant is different than the S/T model.
Ten samples from W/U models were analyzed in 2 separate GM labs. The
results do not indicate any strong correlation between samples.
The root cause is determined to be the same as the S/T: operation for an
extended period of time with a low level of coolant."
They must be fairly sure that the pressure cap will alleviate the
"Evaluate cooling system modifications to achieve a permanent
repair to the S/S issue:
A Stant spring center cap appears to provide the most cost-effective
recommendation to address the S/T contamination issue given lead times,
relative risk and product lifecycles."
Here's more on the pressure cap situation. Plus, they're giving good
advice to their test lab personnel.
Discontinue use of Sundram drop center radiator caps mounted at an
Modify durability test cycles to incorporate vehicles running lifecycle
with low level of coolant in radiator.
Develop backup plan to replace DEX-COOL in the event marketplace
perception deteriorates further.
Discontinue use of stopleak pellets in GM plants."
Internal survey results show a startling amount of contamination on the
Survey: A random survey of 343 1996 and 1997 4.3L equipped S/T trucks
was conducted in the last 6 months of 1996. Percent of vehicles with
Low/Moderate contamination or greater, as measured on radiator cap:
Moraine Facility: 1996 = 37%; 1997 = 36.2%
Linden Facility: 1996 = 17%; 1997 29%"
11. More of the same, but it eliminates the mystery of how the coolant
get low in S/T Blazers.
"Determine the "red X" on S/T w/4.3L:
When a Sundram Drop center design radiator cap is mounted at an angle,
the design is sensitive to allowing debris to get under the valve and
keep it open. Once this occurs, the valve will fail "open" and
additional coolant will be lost more rapidly.
Iron oxide as the result of extended operation with a low level of
coolant and a failed "open" radiator cap, is the root cause of
the S/T coolant corrosion issue."
There's more, but I may not add it until this next print edition of Cool
Profit$ Magazine is published. If I add material, I'll notify subscribers
to the free goHTSN.com newsletter.
End of Part 3b. Check this site often as it is still a work in
progress. Here's links to the follow-up DEX-COOL articles:
(Read first, please)
2007, Part 1: Revising A Less-Than-Accurate Report
2007, Part 1a: 5.7L V8 Engine Sludge and Gasket Change
2007, Part 2: Revising Continues, But What's 2-EHA?
2007, Part 3: Now Its All Up To The Judges and Juries
¤ DEX 2007, Part 3a: General Motors DEX-COOL Memos
© 2007 All Rights Reserved
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