Yanmar 4TNE88 — Checking the thermostat and thermoswitch
Testing & diagnosis · Thermostat / thermoswitch
For the Yanmar 4TNE88, from the Yanmar service manual.
Applies to: Yanmar 4TNE88, Yanmar TNE series engine
Procedure
- Put the thermostat into water in a container and heat while measuring water temperature.
- Make sure the thermostat functions at 69.5-72.5 C.
- Put the thermoswitch into antifreeze or oil and heat while measuring liquid temperature.
- If the tester shows continuity at 107-113 C, the thermoswitch is acceptable.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Thermostat 69.5~72.5 C; thermoswitch ON 107~113 C
Full service-parts list: Yanmar 4TNE88 →
Source: Yanmar 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.