Product Description
Cummins 3957912 — Valve Stem Seal (Top Hat Style) for 5.9L 12V 6BT
MPN: 3957912 | Also Known As: valve stem oil seal, “top hat” seal | Qty Required: 12 per engine (sold individually)
Why This Part
- ✓ OE sealing to control oil at the valve stem and reduce oil consumption.
- ✓ Top-hat design helps prevent the seal from riding up under boost.
- ✓ Direct-fit for 5.9L 12V 6BT with top-hat style seats/retainers (see notes).
- ✓ Sold individually so you can order exactly 12 for a complete set.
Quick Specs
| Type | Valve stem seal (intake/exhaust), top-hat style |
|---|---|
| OE Part # | 3957912 |
| Engine | 5.9L 12V Cummins 6BT (automotive), plus 4BT/6BT industrial—verify by ESN |
| Qty Required | 12 per engine (sold individually) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1993 | 5.9L 12V 6BT | D/W 250/350 |
| 1994–1998 | 5.9L 12V 6BT | Ram 2500/3500 |
Industrial/Off-Highway: Common on 4BT/6BT (B-Series). Always confirm by Engine Serial Number (ESN).
Compatibility Notes: Many OEM 12V heads originally used an older seal design. Top-hat seals may require updated retainers/rotators or light machining. If your head already has top-hat seats, these are direct-fit. Always verify by head casting and component style.
Often Paired With
- Set of 12 seals (order quantity 12 for a complete engine)
- Valve retainers/rotators (upgrade when needed): 3957913 (retainer), 3957914 (rotator)
- Valve collets/locks: 3900250
- Valve springs/valves if wear is present
What’s In The Box
- (1) Genuine Cummins Valve Stem Seal (3957912)
- Sold individually; order 12 for a complete engine set.
Install Tips
- Use proper valve-spring compressor tools; protect valve stems during install.
- Lightly oil the seal lip; press squarely onto the guide until fully seated.
- If converting from old-style seals, confirm retainer/rotator compatibility or machine per shop guidance.
FAQ
WILL THIS FIT MY 1989–1998 5.9L 12-VALVE?Yes—3957912 is the OE top-hat style valve stem seal for 5.9L 12V 6BT applications. Verify head/seal style before ordering.
HOW MANY DO I NEED?Order 12 seals for a complete engine (one per valve). Sold individually.
DO THESE FIT BOTH INTAKE AND EXHAUST?They’re commonly used on both when the cylinder head is set up for top-hat style seals. If your head is still the early style, an update may be required.
DO I NEED TO MACHINE THE HEAD?Only if you’re converting from the original early seal style. Many aftermarket or updated heads already accept top-hat seals.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 3957912. We also carry quality aftermarket equivalents if desired.
