General Motors — Testing Coolant For Alkalinity
Maintenance · Fresh-water cooling system
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
- Obtain red litmus paper from a local supplier.
- Remove the pressure cap from the coolant filler neck and insert one end of the litmus paper into the coolant.
- If the red litmus paper turns blue, the coolant is alkaline and does not need to be replaced; if it remains red, the coolant must be replaced.
Tools required
- red litmus paper Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Replace DEX-COOL coolant every five years
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.