Auto Service World
Feature   October 1, 2006   by Auto Service World

Countertalk: Knowledge Building: Understanding Dex-Cool

Dex-Cool, the General Motors-licensed long-life coolant, has been around for a few years now.

In that time it has come under fire as the purported cause of everything from premature water pump wear to outright gasket failures.

Engine builders, and those selling gaskets for in-bay engine work, should be aware that despite the argument from countless lawsuits south of the border, and the threat of lawsuits north of the border, General Motors and the coolant supplier ChevronTexaco remain adamant that the Dex-Cool coolant used in much of GM’s fleet is not responsible for the intake manifold gasket failures, as discussed at length in the July issue of Jobber News.

As such, GM remains insistent that only approved virgin or recycled versions of the Dex-Cool product be used to cool any GM engine made in 2005 or before.

In fact, the company has stated that should the use of non-approved virgin or recycled Dex-Cool or deviations in the form of alternate chemicals be in play could jeopardize the system.

GM has stated that other, non-tested products could certainly degrade the integrity of the cooling system, and as such, the use of an unaffiliated coolant could actually place the coolant system warranty into question.

Therefore, the following are the only current licensed and approved sources for virgin Dex-Cool and Dex-Cool inhibitor packs used in the recycling process.

It is very important to understand that products advertised as “compatible with” or “recommended” for use with Dex-Cool have not been tested or approved by GM, and it is the position of the company that these coolants play a role in the early degradation of the system. They are not considered by the company to be a full warranty (five-year, 240,000 km) product.

Approved providers, i.e. those who have been evaluated by the company and meet all specifications, are: GM Vehicle Care, AC Delco, ChevronTexaco, Shell, and Prestone.

Recycling Dex-Cool

The recycling system for Dex-Cool is currently quite small, but is being evaluated by GM and will likely be expanded as demand increases. Currently, Recycled Fluid Technologies is the only licensed provider of recycled Dex-Cool that meets all of the company’s requirements, meaning that if another recycler were used, the warranty would likely be voided.

Seal Tabs

It should be understood that seal tabs should not be used as a regular maintenance item, as they tend to cause a discolouration of the coolant liquid itself if they are used in excess. This has a tendency to happen if tabs are used repeatedly over the maintenance life of the vehicle. In short, seal tabs should only be used when diagnostics have failed to repair a small leak in the cooling system.

Water Quality

The overall integrity of the coolant system is highly dependent on both the quality of the coolant itself and of the water used with it. While GM insists that Dex-Cool has both enhanced protection features and extended life capabilities, they claim that these can both be jeopardized by poor quality water. It is important that any water mixed with coolant is either distilled or de-ionized.

“Pink” Dex-Cool

A common complaint regarding the Dex-Cool product is that it may change in colour, from its original orange colour to a pinkish one. This is reportedly caused by slight inconsistencies in the mixing of the dyes, and GM claims that it has no effect on the efficacy of the product. In fact, it maintains its full warranty. This particular coolant was dyed orange initially to easily distinguish it from other coolants. GM is also reportedly working on a solution to stop this colour shift from happening at all.


Mixing conventional green coolant with this product will degrade the system, and affect the warranty if not corrected immediately. It is suggested that if conventional fluid is inadvertently mixed in, the shop should conduct a double flush, replacing the old fluid with a 50/50 mix of new coolant and clean water.

At the end of the five-year or 240,000 km suggested interval, the coolant should be exchanged. Assuming there is no history of contamination from other coolants, the newly replaced Dex-Cool can be expected to last the same five-year interval.

Suggested Equipment

The standard method suggested for this work is a coolant exchanger. An exchanger can replace nearly all of the old coolant with new product with virtually no spillage, and can actually facilitate waste collection. These machines can also be used to perform more routine maintenance on the system, as an exchanger can be used to lower coolant levels. It is highly recommended that you use an exchanger with a vacuum feature, which allows the tech to remove trapped air from the system. It has been noted that the use of an exchanger provides substantial time savings to the shop over the traditional method of thermocycling and simply topping off the radiator.

Special thanks to the AERA-Engine Rebuilders Association for information used here.

Ticking Noise in Ford Engines, 2001-2006

Some Ford Duratec engines can suffer from a troublesome ticking noise.

According to the Automotive Engine Rebuilders Association, some 2001-2005 Taurus/Sable, 2001-2006 Escape, and 2005-2006 Mariner vehicles built prior to January 2006 and equipped with the 3.0L 4V Duratec engine have been known to exhibit this ticking noise. Usually, this can be identified as coming from the left bank cylinder head when the engine is at normal operating temperature.

Shops or engine builders seeking to identify this issue should run the engine until warm (normal running temperature), and use a mechanic’s stethoscope to determine the location of the ticking. If the noise is coming from the left hand intake camshaft at cylinder number 6 (figure 1), refer to the following service procedure listed below.

1. Remove the left bank valve cover.

2. Rotate the engine clockwise until cylinder number 6 intake cam lobes are pointing up and the valves are fully closed.

3. Remove all of the left-hand intake cam caps individually and reinstall them finger-tight.

4. Note: The camshaft caps must be completely lifted off and then set back into place. Loosening and re-torquing the bolts is insufficient.

5. Torque the bolts in the sequence shown in figure 2, to 72 in/lbs, excluding cam cap number 8L, toward the exhaust side of the cylinder head.

6. Using a screwdriver on each side of cam cap number 8L, apply hand pressure and shift cap toward the exhaust side of the cylinder head.

7. While holding cap in the shifted position, torque fastener number 9 (inboard) first to same as others, then torque fastener number 10, also to 72 in/lbs (figure 3).

8. Reinstall the left hand camshaft cover.

9. Fully warm the engine to normal operating temperature and verify the repair.

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