Cummins/Onan QST30 — Cooling Fan Drive Belt Adjustment - Back Side Idler System
Adjustments
For the Cummins/Onan QST30, from the Cummins/Onan owner's manual.
Applies to: Cummins/Onan G-Drive, Cummins/Onan QST30, Cummins/Onan QST30 engine
Before you start
- Do NOT tighten the inner jam nut excessively; the spring retainer will bend and the control rod will fail.
- The fan belt idler is under tension. Do NOT allow your hands between the idler and belt or fan hub.
Parts for this job
- ST669 Belt Amazon eBay $204.59
Part numbers from the service-parts list for Cummins/Onan QST30. Verify against your serial number before ordering; some links are affiliate links.
Procedure
- The fan belt must be installed and under fan idler arm spring tension.
- Turn the adjusting screw until the end of the slot on the lower control rod end touches the spacer.
- Note that one of the nuts has left-hand threads.
- Hold the adjusting screw and tighten the two jam nuts.
- For control rod with spring, turn the inner jam nut until spring retainer washers touch the cylinder.
- Hold the inner jam nut and tighten the outer jam nut.
Tools required
- Socket and breaker bar Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Fan idler control rod capscrews 90 N-m [65 ft-lb]
Full service-parts list: Cummins/Onan QST30 →
Source: Cummins/Onan 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.