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SKU:
NLT1X00429
Ships for free in 2–4 business days.
Cummins 5.9L 12-Valve Tappet Pushrod Cover 3990737 3990738 3990730
$89.99
In Stock
$89.99
Sale price
$89.99
Regular price
This tappet and pushrod side cover replaces Cummins 3990737, 3990738, and 3990730 on compatible 5.9L 6B and 6BT 12-valve diesel engines.
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Compatible Models
We do our best to list all compatible models. Although this may be the part you need, your exact model may not appear below.
Compatible equipment / model
- Cummins 6B 5.9L 12-valve engine using 3990737, 3990738, or 3990730
- Cummins 6BT 5.9L 12-valve turbo engine using the listed cover
- 1989-1998.5 Dodge Ram 5.9L 12-valve applications only when the cover configuration matches
- Industrial and agricultural 6B-series installations with the listed references
Product Overview
Oil running down the side of a 12-valve block is often blamed on the oil pan or front cover when the tappet cover gasket is actually leaking higher up. A warped, cracked, or corroded cover can keep a new gasket from sealing.
The cover closes the side opening used to access the tappets and pushrods. This is a mechanical cover—not a 12-volt electrical part. Compare breather provisions, bolt pattern, contour, gasket surface, and interference with the injection pump and accessories.
Key Features & Performance
- Side tappet / pushrod access cover
- Crosses to three Cummins references
- For selected 5.9L 12-valve 6B/6BT engines
- Replaces a bent, rusted, or cracked cover
- New aftermarket cover
Replaces Part Numbers
- 3990737
- 3990738
- 3990730
Common Uses
- Repairing an oil leak from a distorted cover
- Replacing corrosion around the gasket rail
- Servicing tappets or pushrods when the original cover is damaged
Technical Specifications
- Product Type: Engine Tappet / Pushrod Cover
- Primary Application: Cummins 6B and 6BT 5.9L 12-valve engines
- Package Quantity: 1 cover
- Condition: New
- Replacement Type: Aftermarket
- References: 3990737; 3990738; 3990730
- Engine Family: Cummins 6B / 6BT 5.9L
- Valve Configuration: 12-valve
- Location: Engine block side
- Condition: New aftermarket
Installation & Fitment
- Clean the engine and confirm the leak source
- Remove interfering components according to the service manual
- Straighten or clean mating surfaces and use the specified gasket and sealant
- Tighten evenly to the low cover-fastener torque and inspect after a full heat cycle
Compatibility Notice
Northline Parts does its best to list all known compatible models, but the correct part may fit an application not shown.
Model, production date, serial number, connector, dimensions, installed options, and previous repairs can affect fitment. Compare the original component and reference information before purchase.
Frequently Asked Questions
Q: Is this an electrical 12V part? A: No. In the title, 12-valve describes the engine cylinder-head configuration, not electrical voltage.
Q: Can a new gasket seal a warped cover? A: Often not. The flange must be flat and undamaged or the leak can return.
Q: How do I confirm this is the correct part? A: Match all reference numbers, 12-valve engine, bolt pattern, cover depth and contour, breather or port provisions, gasket shape, and accessory clearance.
Q: Is this supplied by the original equipment manufacturer? A: No. This is a new aftermarket item. Brand, model, and part numbers are used only to identify compatible applications.
Part Summary
keywords: Cummins 3990737 tappet cover, 5.9 12 valve pushrod cover, 3990738 side cover replacement, 6BT engine oil leak repair, Cummins 3990730 cover
Brand names, model numbers, and reference part numbers are used for identification and compatibility purposes only. Verify the original component, dimensions, and application before purchase.