• 4387659, F00BH40308 DEF Pump Backflow (Return) Fitting
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Cummins

4387659, F00BH40308 | DEF Pump Backflow (Return) Connector | For Cummins® Engines

4387659, F00BH40308 | DEF Pump Backflow (Return) Connector | For Cummins® Engines

$46.00 USD
$46.00 USD
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Shipping calculated at checkout.
  • FAST Shipping & No Duties
  • Overnight Shipping
  • Easy Return & Warranty

We Pre-pay all Duty, Customs and Brokerage Fees !

Speak to an Expert: Call 1-587-438-8819

Shipping Policy & Expectations

Fast Shipping: We aim to ship all orders the day they are received. Shipping cut-off time is 1PM MST.

Overnight Shipping: Offered but not guaranteed. Delays may occur due to carrier or other external factors.

Shipping Carriers: We use DHL, UPS and Purolator. Delivery times depend on their operations and may vary.

Cross-Border Shipping:

We prepay all Customs duties and brokerage fees.

This simplifies delivery, reduces delays, and saves you money.

Customs inspections may still cause unforeseen delays.

Lost Packages:

If your order is lost, we’ll replace it at no cost to you.

Need Help? Contact our customer support team if you experience delays or have any concerns. We’re here to help.

Warranty & Return Policy

Returns:

  • 7-day return window from the date of delivery.
  • Parts must be unused and in original, unopened packaging
  • No returns after 7 days.
  • You may be subject to re-stocking fees.
  • Shipping charges, duty fees, brokerage fees are non refundable.
  • If your part fails under warranty, we will provide a replacement, not a refund.

Warranty:

  • 1-year warranty on all parts installed by qualified professionals where procedures applicable are followed. We may require documented proof of installation procedure.
  • Shipping costs are not included in the warranty coverage.
  • If a part fails under warranty, we offer a repair or replacement first. If a replacement isn’t possible within a reasonable time, we will refund the part’s cost.
  • DEF Pump warranties require documented proof of maintenance (cleaned tank, replaced filters, and verified installation by a technician). The vast majority of pump failures are due to poor maintenace and contaminated fluid.
  • If your part fails under warranty, we will provide a replacement, not a refund.

Liability:

  • We are not liable for incidental damages (downtime, labor, lost revenue, etc.).
  • Buyers assume responsibility for proper installation by a qualified professional. Simply replacing parts without a full understanding of the nature of the original failure typically leads to subsequent failures.

Read the full warranty policy Here

Call / Chat with an Expert

Customer Support: For any questions or support, reach out to our dedicated customer service team via email at support@aftertreatmentparts.com or call us at +1 (587) 438-8819.  We provide support early in the morning, all day - and even during the evenings, if someone is available.  

Product Overview:
DEF Pump Backflow (Return) Connector PN 4387659 (Bosch F00BH40308) is a replacement return-line fitting for Bosch-built DEF supply modules (dosing pumps). It installs in the backflow/return port of the pump and connects the DEF return line back to the tank. Per Cummins Technical Service Bulletin TSB150089, 4387659 is the existing backflow connector used with Cummins DEF dosing pumps 4387657 (12V) and 4387658 (24V).

Key Features:

  • Direct Replacement: Replaces Cummins 4387659 and Bosch F00BH40308.
  • Wide Cross-Reference: The same Bosch return connector is listed under Cummins, CAT, Hino, Volvo, John Deere, Nissan, Perkins and Case IH part numbers (see below).
  • Sold Individually: One backflow connector.

Compatible Connector Numbers: Cummins 4387659, Bosch F00BH40308, Dinex 5EL016, CAT 423-3253, Hino S17M0E0031, Volvo 24204464, John Deere RE549605, Nissan 20456LC40A, Perkins T400381, Case IH 47364249

Fits DEF Pumps: Cummins 4387657 (12V, Bosch 0 444 042 134), Cummins 4387658 (24V, Bosch 0 444 042 137)

Installation Notes:

  • Torque the connector to 4.5 N·m (40 in-lb). Do not over-tighten.
  • Cummins TSB150089: pumps 4387304 (12V) / 4387305 (24V) use the revised backflow connector 4387302 instead. Confirm which connector your pump and application require before ordering.
  • CAT describes 423-3253 as a backflow connector with an integral filter and check valve. Please verify your part number when replacing a CAT connector.

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