Cummins/Onan — Charge Air Cooler Leak Check
Testing & diagnosis
From a Cummins/Onan owner's manual covering: 4B3.9, 4BT 3.9, 4BTA 3.9, 6B5.9, 6BT 5.9, 6BTA5.9, B5.9-160, B5.9-175, B5.9-190, B5.9-210, B5.9-230. Check it applies to your exact model before use.
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Procedure
- Remove inlet and outlet hoses from cooler. Remove CAC.
- Install cap over outlet side. Install pressure gauge and shop air supply to inlet side.
- Apply 276 kPa [40 psi] air pressure.
- If pressure drop is 35 kPa [5 psi] or less in 15 seconds, cooler is okay.
- If greater, repair or replace. Leak tank can locate leak.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 276 kPa [40 psi]
- 35 kPa [5 psi] or less in 15 seconds OK
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.