General Motors — Draining Fresh-Water Cooling System
Maintenance
From a General Motors owner's manual covering: Carb 5.7L, MP 5.0L, MP 5.7L, MP 6.0L. Check it applies to your exact model before use.
Procedure
- Remove drain plugs to drain coolant: heat exchanger, fitting on bottom of exhaust manifolds, risers, and cylinder block (one each side).
- Remove the large hose from the engine block water circulating pump, or the drain plug on the circulation pump.
- Remove drain plugs to drain raw water: oil cooler, heat exchanger, and fuel cooler canister (returnless fuel system only).
- After the system has drained completely, coat all drain plugs with PerfectSeal (or equivalent) and reinstall in the proper locations.
- Reinstall the hoses on the water circulating pump and exhaust manifolds and tighten the clamps securely.
Source: General Motors owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.