Detroit Diesel — Checking of Thermostat
Testing & diagnosis
From a Detroit Diesel service manual — check it applies to your exact model before use.
Before you start
- Do not ever use a welding torch or soldering gun as a source of heat.
- Make sure the thermostat is not touching the sides of the container.
Procedure
- Hang the thermostat by a wire inside a container filled with water.
- Heat the water with a suitable heating element, stirring occasionally.
- As temperature climbs to around 75°C, slow the rate of heating to about 1-2°C per minute.
- Check the main valve has started to open at 81-85°C (177-185°F).
- Check the main valve is fully open at 95°C (203°F).
- Check the main valve minimum lift of 8 mm (0.3 in.).
- Check the short circuit valve is fully closed at 92°C (198°F).
- Check the short circuit valve minimum lift of 6-7.5 mm (0.24-0.295 in.).
- Replace the thermostat if any of the values is not met.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Main valve starts to open 81-85°C (177-185°F)
- Main valve fully open 95°C (203°F)
- Main valve minimum lift 8 mm (0.3 in.)
- Short circuit valve fully closed 92°C (198°F)
- Short circuit valve minimum lift 6-7.5 mm (0.24-0.295 in.)
Source: Detroit Diesel 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.