I have a 92 vette with the LT1 engine. I'm going to flush the radiator or have it done. The manual says to to add six cooling system sealer pellets when refilling after after the flush. Do these pellets seal the system? I guess they are really necessary.

 

I put some in my Cadillac to seal the head gaskets and they worked great. Picked them up at the GM dealer for about 6 bucks. You gotta crush them up too.

 

It's been since the 90s that I worked for an AC Delco shop, but if memory serves, those things are made out of almond shells and some other stuff and GM highly recommends you put them in every system after servicing.

 

Sealer pellets ? I hope these aren't like the stop leak junk they sell at the parts stores. Those things will plug up a leak and plug the heater core while they're at it. Must be something different. I used to sell auto parts 10 years ago as a kid and the bars leak and all of the ones we sodl were murder on the heater core.

 

my tank seam weeped after a flush and 1 of the pellets cured it.
i dont know if i would use 6 of them though.
theres tons of opinions on the things,and gm no longer uses them.
i think they were necessary in early 4100 caddy engines and a pretty good thing to add to an lt1 (or any cast block/aluminum head engine) but thats only my opinion.
try and find the GM pellets though,dont use bars leaks or alumiseal or risk core plugging problems as stated earlier.
(theres other products with the same makeup of the gm pellets but i cant remember what lol)

 

I had great luck with Bars Leak and it lasted for the 12 years I owned the car (85 and 88 Z51's). Bars Leak is used by all factories if there is a leak before leaving the factory.

 

Does the manual say six? Or two?

The FSM for my '89 states to add TWO pellets.

If you do proceed, use the same type of coolant for the refill
- do not change between glycol and Dexcool. Use distilled water
for the mix, not tap - if someone else is performing the work, buy
a couple of gallons of distilled (not mineral) water at a pharmacy
to take to the appointment - then they have no excuse. (Once
a shop used water from their staff room drinking bottles in response
to my request that they use distilled water.)

The p/n for the cooling system tablets that GM recommends is
#3634621 for a pkg of 6 pieces. Get these from a GM dealer or
ACDelco outlet.

Going forward, change coolant at least every two years for best
results from the additive package.

.

 

GM issued a tech bulletin a few years ago that said to discontinue the use of the cooling system pellets in C4 systems. Apparently the excessive use of the tabs can eventually clog up the cooling tubes in older radiators and actually reduce the cooling efficiency of the radiators.

Definitely use distilled water for the refill step in a cooling system flush. You may even want to use distilled water as the final flush step. The service manual recommends flushing the system 3 times - drain old coolant, refill with water, run motor for a few minutes, drain and repeat.

Remove the plastic overflow tank from the car and clean it up to make sure you get any junk from the bottom of it. It gets reinstalled later.

To get all of the old coolant or flush water out, you do need to pull the knock sensors from the bottom of the block. There is one on each side and a 22mm socket is needed to remove the sensor. There is a small metal cover that must be removed to get to the sensor. Don't use any sort of teflon tape or liquid teflon on the threads when re-installing. The threads provide the electrical ground for the sensors.

The LT1 systems uses 16 quarts of coolant. With the system empty, pour in 2 gallons of ethlyene glycol (green) concentrated coolant. Make sure the two bleed valves are open (one is on the thermostat cover, the other is on the lower corner of the throttle body on the driver's side).

Then begin to add distilled water. When there is a steady stream of coolant coming out of the bleed valves, close them and finish filling to the base of the filler neck. Don't allow the coolant to drain down over the OptiSpark!! Place towels under the bleed valves or form some aluminum foil to let the coolant drain away from it.

Start the engine and let idle. Watch the coolant temps carefully. When the stat opens, add more water to the tank and fill to the base of the neck. If the coolant temps get too high (240+) shut the motor off and let it cool before restarting.

Once you have the water level staying at the filler neck, replace the cap, reinstall the overflow tank and add a 50-50 mix of coolant and water to the COLD line.

The service manual also recommend that the engine should go thru 3 complete cycles of coolant temp ranges (cold to operating temp and back to cold) before any full-throttle opeatrion. This insures that any air pockets left in the system will bleed out. Check the coolant level in the overflow tank and add as needed.

 

If the car isn't leaking, I won't use them or anyother sealer.

 

What GM recommended in the past for Cadillacs was the Bar's Leak Conditioner tablets. I put them in my 95 VERT regularly (every 15000 miles) as a conditioner. Recommended in the 84-96 101 things to do for your vette. Good to flush the system every 30000 miles or so and replace with clean green

 

For some of us, 30,000 mi could easily mean well over five years
between changes.

The electrolytic reaction takes places regardless of miles accumulated.
My vote is still to change on a 2 year (max) cycle. If major new
aluminum components (rad, heads, intake) are added, I've decided
to change the fluid again within months of the swap as I've learned
that the new components accelerate consumption of the coolant
additives.

.