Originally Posted by OdinsRage
Some say northstars should have this also...
I use Bars Leak in my N* ('98 Eldo).
Though I would recommend that you add the pellets/BarsLeak through the radiator hose and not the surge tank. GM recommends the lower hose but I've had no difficulty adding it through the top hose.
I believe the aim is to have the material in the radiator.
The surge/expansion tank, while part of the pressurized system, is not in the flow. Rather it is located at the highest point in the system, above the engine and plumbed with smaller hoses to allow the escape of air (cavitation) produced by pump activity.
There is a great deal of info about this at Cadillacforums.com. The site is very similar to this one and just as easy to navigate. Do a search and you will find a great deal of info.