Product Description
Stop seepage at the thermostat housing and keep your 5.9L 12-valve running at the right temp with the MAHLE C31421 Coolant Thermostat Gasket. This molded-rubber OE-style seal restores a leak-free interface between the thermostat and housing on 1989–1998 Dodge Ram Cummins trucks—perfect for fresh installs or maintenance refreshes.
Fitment
- 1989–1998 Dodge Ram 2500 / 3500 — 5.9L Cummins 12-valve (6BT)
Cross-Reference / Alternatives (Mahle on CPP Diesel only)
- MAHLE C31858 — Coolant Thermostat Gasket (2003–2007 Cummins 5.9L)
- MAHLE VS50416 — Valve Cover Gasket (2003–2005 Cummins 5.9L)
Notes
Clean both sealing surfaces and inspect the housing for corrosion or warpage before installation. Lightly lube the gasket, align carefully, and torque the cover to spec in a criss-cross pattern.
FAQ
Will C31421 fit my 1994–1998 12-valve?
Yes. C31421 is designed for 5.9L Cummins 12-valve (1989–1998) thermostat housing applications.
Do I need sealant?
Generally no—this is a molded-rubber OE-style gasket. Follow factory service information for your specific housing if corrosion is present.
How should I prep the surfaces?
Remove old material completely, wipe with a non-residue cleaner, and ensure a smooth, dry, oil-free surface before installing the new gasket.
Specifications for Mahle C31421
| Attribute | Value |
|---|---|
| Brand | MAHLE |
| Part Number | C31421 |
| Engine Compatibility | 1989–1998 Dodge Ram 2500/3500 — 5.9L Cummins 12-valve |
| UPC | 757522711272 |
| GTIN | 00757522711272 |
| Shipping | Calculated at checkout |
| Prop 65 | This product can expose you to chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Learn more |
