Product Description
Interstate-McBee M-3963991 – VGT Turbo Coolant Line Sealing Washer (2007.5–2018 6.7L Cummins)
Direct-replacement sealing washer used on the variable-geometry turbo (VGT) coolant hard-line connections on 6.7L Cummins ISB engines. Restores a proper, leak-free seal at the coolant banjo/line interface. Sold individually.
- OE-style fit: Matches the size and profile specified for VGT coolant line joints.
- Leak control: Helps prevent coolant seepage after turbo or line service.
- Service-friendly: Ideal to replace whenever a coolant line is removed or re-torqued.
- Value: Interstate-McBee quality as an aftermarket replacement for Cummins reference 3963991.
Specifications
| Brand | Interstate-McBee |
| Part Number | M-3963991 |
| OEM Cross | Cummins 3963991 (sealing washer) |
| Application | VGT turbocharger coolant hard-line connections |
| Sold As | Each (1 sealing washer) |
Vehicle/Engine Fitment
Always verify by engine serial number (ESN) when possible.
- Ram 2500/3500 with 6.7L Cummins ISB
- Model Years: 2007.5–2018
- Turbo Type: VGT (HE351VE/HE300VG and related)
- Other on-highway 6.7L Cummins ISB applications using Cummins 3963991 at VGT coolant joints.
What’s Included
- (1) Sealing washer, P/N M-3963991
Recommended/Related Parts
- VGT coolant hard-line(s) and banjo bolts (as required)
- Fresh coolant compatible with Cummins specifications
- New sealing washers for any other disturbed coolant/oil line joints
Install Notes
- Do not reuse old sealing washers—replace anytime a joint is opened.
- Clean mating surfaces; no debris, nicks, or corrosion at the seat.
- Lightly oil the washer, align line and joint squarely, and torque fasteners to factory spec.
- Bleed/prime the cooling system and check for leaks after warm-up.
FAQs
How many washers do I need?
Quantity depends on how many coolant line joints you open at the turbo. Order extras to cover both sides of the disturbed connections.
Will this fit my 2012 6.7L Cummins?
Yes—this washer is used on 2007.5–2018 6.7L Cummins VGT coolant line joints. For absolute confirmation, verify by ESN.
Is this an OEM Cummins part?
No—this is an Interstate-McBee aftermarket replacement that cross-references Cummins 3963991.
