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Caddyinfo's Cadillac How-To Section

Cadillac Sealant Confusion

Subject : RE: Sealant Confusion?
MessageDate : 9/11/2002 1:00:23 PM
Posted By : bill
Cadillac Year : 2003
Cadillac Model : DeVille
Message : I think there are several ways the confusion exists....but I don't in any way sense that this is a means of avoiding warranty expense...??? If GM stops putting the sealant in at the factory (which was done around 97-98) why would there be a reason to ignore a warranty claim if the dealer did not put it in...???

If anything, the elimination of the colant supplement has driven up warranty as minor porosity seepage and an imperfect gasket surface that would functionally seal and never seep with the coolant supplement will now show up and be repaired/replaced under warranty. The arguement could be made that elimination of the colant supplement proves that the sealing integrity is dramaticlly improved on the engines and the customer will get service on any sealing imperfection as they will now be high lighted by the lack of the factory installed supplement.

The implementation of DexCool and the elimination of the coolant supplement for the factory fill of coolant occurred at roughly the same time in history....just a coincidence.....but many people took this as a sign that the coolant supplement was not compatible with or was not required with DexCool. In fact, there is nothing with DexCool that negates the need for the supplement nor is there any reason not to use the supplement with DexCool.

There were some cases with the 4.3 V-6 engine in specific where the cooling systems would act up if the system was run low with DexCool. The uncovered iron surfaces in the engine (due to low coolant) would develop surface rust and then that rust would wash into the system as coolant sloshed around in the engine. As the DexCool built up red rust particulates it would foul the sealing surface of the radiator cap and cause it to unseat and exacerbate the low coolant condition with overheating due to loss of pressurization. Unfortunately, the coolant supplement was viewed as a detriment to this particular failure mode as the fibers (that would normally seal a leak) would coagulate with the red rust particulates and make the cap seal unseat even worse. For this reason the coolant supplement/sealer was eliminated at the factory first on the 4.3 V-6. As a result of successful deletion of the supplement and the ongoing improvement in seals and gaskets and casting integrity the move was made to eliminate the sealer from all engines in GM's lineup a number of years ago.

This chain of events creates ANOTHER source of potential confusion because, even though it is technically correct to say that a 2000 Northstar does not get and does not need the coolant supplement, the change was NOT RETROACTIVE to previous models. Unfortunatele, when most of the field organization and mechanics in general see that the supplement is no longer being used they stop using it period, even on the older model engines PARTICULARILY THE 4.X ENGINES which still require it.

The sealer is absolutely mandatory and will continue to be mandatory for the 4.x engines as there exists the possibility for an internal coolant leakage/seepage into the engine oil in that engine design. Many engines by many manufacturers have this situation so sealer in the cooling system is recommended for any of them!! Particularily as the 4.x engines age/mileage increases the potential for a gasket failure due to fatigue, corrosion, or just old age becomes greater and the need for the insurance provided by the coolant supplement becomes much greater. Coolant into the oil, even in small amounts over time, can lead to oil depletion and catostropic engine wear at cam lobes on non-roller lifter engines and at the distributor gear drive on all engines.

The Northstar engine is designed such that an internal coolant leak into the oil is highly unlikely, even with a failed gasket. Only in the most catostropic gasket failures can coolant get into the oil and by then that is the least of the concerns!!! So the need for the supplement is dramaticlly reduced or eliminated on the Northstar of all years. The sealer is still recommended for insurance of good cooling system integrity against any external leaks. It is a very effective product (if the correct stuff is used correctly) and will even help protect against leakage of coolant into the combustion chamber if a head gasket does start to get weak or fail. Any Northstar with high miles/age can start to suffer from gasket fatigue and corrosion and even on newer and low mileage engines some casting porosity can open up over time leading to a leak or seepage that is harmless and cured by the coolant supplement. I still recommend it's use but it has been discontinued at the factory on the newer engines.

Another reason for the coolant supplement is leakage at the water pump seal. The tiny fibers in the coolant supplement act to microscopically "scrub" the surface of the water pump seal to keep it clean and seated. Impurities on the seal surface can unseat the seal and cause seepage. Use of the supplement will help prevent this in any engine.

BTW.....the coolant supplement is just a sealer. It is the product of the company that markets under the BarsLeaks brand and is made up of ground up ginger root and walnut shells.... The supplement or sealer has nothing to do with controlling the pH of the coolant, corrosion inhibitors or anything like that. It will not "protect" gaskets from corrosion or failure. It is just a sealant. The tiny fibers of the sealant collect in a leak path and swell when exposed to air on the "leak" side thus plugging the leak. The fibers get chopped up over time by the water pump vanes and become less and less effective thus the supplement needs to be replaced/replenished with time. This is also the source of the "mud" or sludge sometimes observed in the tanks of radiators in high mileage engines. The supplement is just carried in suspension in the coolant. It does not dissolve the way salt dissolves in water. That is why the supplement needs to be added to a radiator hose or radiator tank where it can be exposed to the bulk flow of the coolant rather than be poured into the pressurized surge tank of a Northstar or the coolant recovery bottle of a 4.x.

Hoefully this sheds some light on the subject and is maybe a good item for the FAQ.


I keep hearing (third-hand of course) that Dealers are not generally putting in the coolant sealant supplement required in the manuals. They think there was a later TSB that cancelled the sealant supplement.

I wonder if they are getting confused by document 742292, DEX-COOL Engine Coolant Information #00-06-02-006, which says:
Sealing tablets are not used at the assembly plant for most models. Sealing tablets are generally not necessary and should not be used as a regular maintenance item after servicing an engine cooling system. The use of sealing tablets can, in some cases, produce contamination of the cooling system and/or severe discoloration of coolant.

Which is probably fine for the iron engines, but does not apply to the aluminum engines. Here is the shop manual warning for the Northstar:
This engine uses DEX-COOLŪ and GM coolant supplement (sealant) P/N 3634621 specifically designed for use in aluminum engines. Failure to use the engine coolant supplement (sealant) and the approved coolant antifreeze could result in major engine damage. When refilling the cooling system, add three pellets of the engine coolant supplement sealant GM P/N 3634621 to the lower radiator hose.

Any chance that the Techlink or other info sources could make this clearer to the Dealers? Clearly some are confused.

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