Inner air filter (safety element) with part number 4W6691 from the REDX offer. It is a safety cartridge, mounted inside the main filter, dedicated to classic Caterpillar (CAT) B-series backhoe loaders (e.g., 428B, 416B). The filter has a rubber gasket ensuring perfect tightness and protects the engine in case of outer filter damage.
REDX filters are designed for maximum engine protection. The safety cartridge features denser filter media that traps the finest dust particles that could pass through the main filter.
| Machine Type | Models |
|---|---|
| Backhoe Loaders | 416, 416B, 426, 426B, 428, 428B, 436, 436B, 438, 438B |
Filter dedicated to older CAT models. Check the dimensions of the old cartridge before purchasing.
Filter 4W6691 is an inner cartridge. It works together with the outer (main) filter. We recommend replacing both filters simultaneously in case of heavy contamination of the safety element.
The inner (safety) filter must not be cleaned or blown out. If it is dirty, it means the main filter has failed. In this case, you must replace both filters with new ones immediately to avoid engine seizure.
Filter 4W6691 is the engine's last line of defense against dust.
📞 Can't find the part you're looking for?
No worries. Our website features only a few thousand of the over 60,000 parts we have in stock. Contact us – we likely have what you need readily available!
No. Safety (inner) filters are never washed or blown out. Their structure is too delicate and dense. Always replace with a new one.
Usually not. C-series machines (e.g., 428C) often had modified filter housings. Always check the part number. This filter is typical for A and B series.
CAT B-series backhoe loaders, which this filter fits, were introduced in the early 90s. They were groundbreaking thanks to the introduction of the curved excavator boom (banana boom), which made digging deep trenches and loading dump trucks easier.
Do you have doubts or need confirmation to avoid costly downtime? Call us. Our experts will help you select the right part to get your equipment back to work as quickly as possible.
Data sheet
Specific References
Manufacturer
Responsible person
See also similar products



Suitable for CAT 416, 416B, 426, 426B, 428, 428B, 436B machines

















