Thanks guys.. this topic seems trivial but I really want to do it right. The original coolant was in there for 10 years and 100,410 miles. Had it flushed at the local Buick dealer in 2007 and Dex-cool put in. I let it go WAY too long (10 yrs) and 7,000 miles later had an intake failure at the back (driver side) of the plenum, with coolant leaking down onto the trans-axle housing area. GM did a good job in replacing/sealing upper and lower manifold but it was expensive. To hold costs down, I opted to put the coolant back in the motor instead of another "coolant exchange." That was in 2009.
It's been five years and I want do another coolant change according to FACTORY procedure at minimum. Have called several shops and stopped by a few more. Am in discussion with a Chevrolet dealer, with the Asst. Serv. Mgr. and they are using a
MOC coolant machine and will put Dex-cool back in. Adding gold Supplement pellets which I saw at the nearby Delcoline wholesaler last week (6-cyl takes two tabs from pack of five, Caddies take all five?) is still up in the air.
See the scans below from 97 Riv Owners Manual. The first view defines the change interval, and the second view defines using the supplement/sealer for a "
complete coolant change." This makes sense to me, because a couple shops have said there's been trouble flushing older cars where leaks and other issues develop.
So adding sealer tabs is still up in the air, as one reply above advises. If the manual is specifying sealer, then it can't hurt any? huh? and I believe the small shops that describe trouble after flushing older engines. I'd like to avoid another engine gasket job and/or corrosion of dissimilar mating surfaces.
- Edit -
Here are the Seal Tabs, 10-108. They look like packed fine gold granules.
-Ed