Flushing Coolant

[Chetzki]

I've drained my radiator and reservoirs (at least most of the upper reservoir), but how do I get all my coolant out of the engine and the rest of the lines? I only drained out less than 2 gallons and I see my thermostat housing is still full to the brim.

Do I have to fill with water, let it heat up until the thermostat opens with the heater on while draining and running water in the upper reservoir to get a true flush, or is that too risky? Is there another way to get everything out? The sections I've drained are less than 1/2 the total coolant capacity.

Yes, this is "The Evil Red Stuff" and I'm going back with the Red Stuff. I'm not sure, but the gaskets and materials chosen that touch the coolant may have been selected assuming the additives in Dexcool would always be present. A mechanic explained that was true for my 1996 GM truck. I was willing to experiment with the truck so I switched to the green stuff after the intake manifold gasket sprung a leak (this is a common leak and rumour has it that that leak is caused by the Red Stuff). Now, about a year later, my water pump went out (age or coolant??? I wonder and the world my never know).

The good news about my car though, the fluid was clear but the lower overflow reservoir had a lot of solid deposits. When I disconnected the coolant lines to the TB, they were caked with deposits on the insides of the hose reducing the ID of the hose to about 1/2 of what it is. I'm assuming that is because the velocity through those lines are not high enough to prevent deposition. The TB is by-passed now, so I don't care.


Thanks,
Chetzki

[c4cruiser]

The coolant in the block has to be drained by removing the knock sensors on either side of the block just above the oil pan rail. On the right side, look for a small metal heat shield just in front of the starter. Two nuts hold the shield to studs on the oil pan rail and it's easily removed. The left side one is just as easy. Remove the wire to the knock sensors and use a 22mm socket to pull them out. Expect a LOT of coolant to come out!

When the old coolant drains out, screw the sensors back in and snug up. Open the bleed valve on the thermostat housing and fill the system with water. Close the bleed valve when a steady stream comes out the bleed valve. Start the motor and let it get to around 200 degrees to open the thermostat. Stop the motor, let it cool and drain again. If your system is fairly dirty, do this 2 more times. While you're doing this, remove the expansion tank from the right side fender well, clean it and re-intall. Don't refill yet.

Once the knock sensors go back in for the last time, apply a light coat of anti-sieze compound (Don't use teflon tape!). Add 2 gallons of Dexcool directly into the surge tank. With the bleed valve open, use distilled water to fill the rest of the system. When the coolant comes out of the bleed valve, close it and finish filling. Start the engine and run to operating temp. Watch for the stat to open and keep a close eye on the temp guage. Don't let it hit 250 or above. When the coolant is flowing in the surge tank, top off to the base of the filler neck and replace the cap. Add about 2 quarts of a 50-50 mix of coolant and distilled water to the expansion tank.

[Chetzki]

Got it done. Thanks for the help!
Chetzki