A GM Engineer who used to post on this site and is extremely knowledgeable posted this a while back: (The initial conversation was about DexCool, but he went on to talk about sealants)
"I personally always recommend the use of the GM coolant supplement pellets ( or the equivalent BarsLeaks products HDC ) to ensure against any internal coolant leaks into the oil. An engine like the 4.3 can leak coolant internally if a gasket starts to fail or something so the coolant supplement/sealer is good insurance against this. It is/was factory installed in that system and needs to be replenished over time and/or as the cooling system is refreshed. I would add 6 of the coolant supplement pellets to ensure a positive seal of the system. It causes no harm and will be perfectly benign unless there is a leak somewhere.
in Cadillac forum:
The GM coolant supplement pellets and the BarsLeaks "golden seal" are the same material. The company that manufactures the cooling system sealer supplies GM with the material in pellet form and also sells under the BarsLeaks brand name.
You can usually find the BarsLeaks "golden seal" powder in the clear tubes at WalMart or ACO stores or most any decent hardware store. The BarsLeaks product that is in the various jars and bottles with brown liquid is acually the same sealant material it's in a kind of "rabbit food" sized pellet that is in the bottom of the jar. It is the same stuff - just soaked in the brown soluable oil material that is obstensably used to "lubricate the water pump". Sounds good. Totally unnecessary. As a last resort the stuff in the brown liquid will work, the pellets or powder without the oil is better.
Under no circumstances should you use the stuff that looks like aluminum or metal shavings. Nasty stuff that will plug heater cores and most anything. Check the BarsLeaks website for more information.
The material is just a sealer to guard against nuisance leaks in the cooling sytem. With aluminum engines it is not too uncommon to get some seepage due to porosity in castings and such and the sealer guards against such leaks that might occur over time as porosity and coldshuts in the castings open up with the thermal cycling of the engine. The supplement/sealer does nothing but seal leaks. It does not protect the engine in any way other than against leaks. The sealant works with both DexCool and conventional green coolant.
You might check the post in the "general Cadillac - non-model specific discussion" category above regarding the coolant supplement. Crushing the pellets is completely unnecessary. That instruction is a carry over from the 4.9 engine where the supplement was introduced into the radiator itself and there was not room in the end tank (due to the oil cooler inside the tank) to get a full sized pellet in. Just pop the pellets into the radiator hose whole and reconnect the hose. They will have turned to mush in the coolant before you have the clamp tightened.
With the Northstar the supplement (pellets/powder) must be installed in the radiator hoses to introduce the material into the bulk flow of the coolant to ensure it is distributed through the sytem. More confusion occurs because people put it into the pressurized surge tank and then run into problems with it plugging the hose from the surge tank to the water pump. This makes them think that they need to crush the pellets. There is little or no flow through the surge tank so putting the material in there will not distribute it through the sytem (so it will not work and they think it is ineffective) and/or it can clog the hose to the water pump because the material just lies there in a lump and does not disperse. The material does not "dissolve" in a classic sense - it stays whole and in suspension in the coolant and is just dispersed as minute particulates through the sytem. So, if there is insufficient flow to get it dispersed it can cause local problems if it is not installed in the radiator hose correctly.
I recommend that you put 6 of the large GM supplement pellets into a 4.9 engine or a Northstar engine. The service manual calls for 3 of the large pellets for the Northstar since less leak protection is needed with the Northstar since it cannot leak coolant into the oil. 6 will provide extra protection from seepages long term and 6 is the recommended dose for the 4.9 engine as the 4.9 CAN leak coolant into the oil so the extra dosage is required to maintain the adequate leak protection.
If you use the BarsLeaks golden seal powder - two tubes in a Northstar. The BarsLeaks pellets that I have seen are about half the size of the GM pellets so I would recommend 10-12 of them.
The stuff is just an organic material. Ground up ginger root. It works because it shrinks when wet and expands when dry. It will "clot" in a leak area and then expand on the "dry" side to seal the leak. That is why it wont clog heater cores. There is no air on the backside of the orifice for the material to expand.
Pellets, powder, crushed, not crushed, top radiator hose, bottom radiator hose. All Okay. Either radiator hose (whichever is easiest to get to) will work the same as the bulk flow of the coolant goes through both to disperse the material through the system. Put it into the radiator directly of the 4.9 so you don't have to disconnect a hose.
The factory puts the sealer/supplement pellets into each new cooling sytem for the Northstar and they don't take the time to crush each of them up! The factory install was discontinued for a few years but is being reinstated due to the low but persisent cases of nuisance seepages and leaks."