Description
Product Overview
The 904-7904 Crankcase Ventilation Breather Filter is a direct replacement for the Cummins ISX 11.9L diesel engine. Designed to filter crankcase blow-by gases and prevent oil mist from entering the intake system, this breather filter maintains engine efficiency and reduces emissions. Compatible with Kenworth T680, T800, T880, W900 and Peterbilt 365, 567 models equipped with the ISX 11.9L engine.
Key Features
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Direct OEM Fit: Drop-in replacement for Cummins part number 904-7904, also replaces 3685528, CV50617, CV50634
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High Filtration Efficiency: Captures oil mist and particulates from crankcase gases, keeping your intake and turbocharger clean
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Heavy-Duty Construction: Built for the extreme operating conditions of Class 8 trucks — high mileage, high heat, and continuous duty cycles
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Emission System Protection: Clean crankcase ventilation reduces carbon buildup on EGR valves, DPF filters, and turbocharger components
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Easy Installation: Bolt-on replacement — typically 15-20 minutes with basic hand tools
Compatibility
| Engine |
Make/Model |
Years |
| Cummins ISX 11.9L |
Kenworth T680 |
2010–2024 |
| Cummins ISX 11.9L |
Kenworth T800 |
2010–2024 |
| Cummins ISX 11.9L |
Kenworth T880 |
2013–2024 |
| Cummins ISX 11.9L |
Kenworth W900 |
2010–2024 |
| Cummins ISX 11.9L |
Peterbilt 365 |
2010–2024 |
| Cummins ISX 11.9L |
Peterbilt 567 |
2013–2024 |
Specifications
| Specification |
Value |
| Part Number |
904-7904 |
| Cross References |
3685528, CV50617, CV50634 |
| Filter Type |
Crankcase Ventilation / Breather |
| Engine Application |
Cummins ISX 11.9L Diesel |
| Material |
Synthetic Media with Metal Housing |
| Replacement Interval |
Every 100,000 miles or annually |
Why Replace Your Crankcase Breather?
A clogged or failed crankcase breather filter leads to excessive crankcase pressure, oil leaks from seals and gaskets, turbocharger oil contamination, and increased oil consumption. On ISX engines, a failed breather is one of the most common causes of rear main seal failure — a repair that costs $2,000+. Replacing this $30 filter on schedule is the cheapest engine insurance you can buy.
Installation Tips
- Locate the breather housing on the passenger side of the engine block (mid-engine, near the air compressor)
- Remove the breather housing cover bolts (typically 4 bolts, 10mm)
- Remove old filter element — note orientation for new filter installation
- Clean housing interior with shop rag to remove accumulated oil residue
- Install new 904-7904 filter element in correct orientation
- Replace cover gasket if worn or damaged (sold separately)
- Torque housing bolts to OEM specification (typically 18 ft-lbs)
Frequently Asked Questions
Q: How often should I replace the 904-7904 crankcase breather?
A: Cummins recommends replacement every 100,000 miles or 12 months, whichever comes first. For trucks operating in severe dust, high idle time, or extreme temperature conditions, consider replacing every 75,000 miles.
Q: What are the symptoms of a clogged crankcase breather?
A: Common symptoms include: oil leaks from front/rear main seals, excessive blow-by from the oil fill cap, increased oil consumption, oil in the turbocharger inlet, and in severe cases — the dipstick popping out under crankcase pressure.
Q: Does this fit my Peterbilt 389 with ISX?
A: Yes, if your Peterbilt 389 has the Cummins ISX 11.9L (not the ISX 15L or X15), this filter will fit. The ISX 11.9L was used in many vocational and regional haul configurations from 2010 onward.
Q: Is this the same as the Cummins OEM part?
A: This is an aftermarket replacement manufactured to meet or exceed OEM specifications. It provides the same filtration efficiency and durability as the Cummins-branded part at a fraction of the cost.
Q: Can a bad breather filter cause DPF issues?
A: Yes. Excessive oil mist from a failed breather enters the intake tract, contributing to carbon buildup in the EGR cooler, DPF, and turbocharger. This increases regeneration frequency and can lead to premature DPF failure.
Related Products
Blog Resources
Learn more about maintaining your diesel engine's breather system — check out our iFJF Diesel Maintenance Blog for installation guides, maintenance schedules, and diagnostic tips.
