Kohler — Test Crankcase Vacuum
Testing & diagnosis · Crankcase breather
From a Kohler service manual covering: CH18, CH20, CH22, CH23, CH25, CH620, CH640, CH670, CH680, CH730, CH740, CH750. Check it applies to your exact model before use.
Applies to: Kohler CH18, Kohler CH740
Before you start
- Carbon monoxide can cause severe nausea, fainting or death. Avoid inhaling exhaust fumes.
Procedure
- Insert rubber stopper into oil fill hole and connect manometer tube; leave other tube open.
- Start engine and run no-load high speed.
- Open clamp and note water level; engine side should be minimum 10.2 cm (4 in.) above open side.
- Close pinch clamp before stopping engine.
- If low/no vacuum or pressure, check breather, seals, gaskets, piston blow by, or restricted exhaust.
Tools required
- Water manometer or vacuum/pressure gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Crankcase vacuum should be minimum 10.2 cm (4 in.) of water
Full service-parts list: Kohler CH740 →
Source: Kohler service 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.