ZTech  |  SKU: 36523641234525

ZTech Engine Thermostat Volvo VNL/D13 | 21613426 21412639

$79.99
Shipping calculated at checkout.

RETURN & REFUND

You have 30 calendar days to return an item from the date you received it. To be eligible for return all parts must meet the following conditions:
• The item must be new, unused, and uninstalled;
• The product must be in salable condition, with no signs of installation (e.g., grease, scratches, or missing components);
• Original packaging is required, especially for branded parts;
• Any item that has been installed, modified, or misused is not eligible for return;
• Unacceptable returns may be shipped back to the customer upon request, at the customer's expense;
• Your item needs to have the receipt or proof of purchase.
We have a Restocking Fee which applies for return items with damaged package. Restocking Fee is 25%-50% of initial purchase.
• Do not tape the original packaging box — Restocking Fee will apply;
• Do not stick any shipping label/sticker on the original packaging box — Restocking Fee will apply;
• We recommend using stretch film to wrap the original packaging box. Use an additional shipping box or envelope to return the item.
You will be responsible for paying your own shipping costs for returning your item. Shipping costs are nonrefundable.

SHIPPING INFO

Standard Shipping — rates calculated at checkout (3-5 business days)
Express Shipping available at checkout (1-2 business days)
Guaranteed Overnight Shipping available at checkout — order before 2 PM PST (Monday–Friday)
International shipping available to Canada and EU — rates calculated at checkout.
All orders processed within 1 business day (excluding Sunday and holidays).

ADDITIONAL PRODUCT INFO

The ZTech Engine Thermostat (21613426 / 21412639) regulates coolant flow in Volvo VNL trucks with D13 and Mack engines, controlling engine warm-up time and maintaining optimal operating temperature. A stuck-open thermostat causes slow warm-up, poor fuel economy, and increased emissions. A stuck-closed thermostat causes rapid overheating and can result in head gasket failure within minutes. ZTech thermostats are calibrated to OEM temperature specifications for reliable operation in heavy-duty diesel applications.

Q: Which trucks and engines does this thermostat fit?
A: Fits Volvo VNL trucks with D13 engines and compatible Mack trucks. Replaces OEM part numbers 21613426 and 21412639.

Q: What temperature does this thermostat open at?
A: Calibrated to OEM D13 temperature specifications — consult product specifications for exact opening temperature rating.

Q: How do I know if my thermostat has failed?
A: A stuck-open thermostat keeps the engine cold and reduces fuel economy. A stuck-closed thermostat causes rapid overheating — both require immediate replacement.

Q: Is this OEM or aftermarket?
A: ZTech aftermarket thermostat calibrated to Volvo D13 OEM temperature specifications.

Q: Should the thermostat housing gasket be replaced at the same time?
A: Yes. Always replace the thermostat housing O-ring or gasket when replacing the thermostat to prevent coolant leaks.

Description

OEM Part Number: 21613426
Also fits / cross-references: 21412639

Fits: ZTech Engine Thermostat Volvo VNL/D13.

This ZTech part regulates engine temperature by controlling coolant flow to the radiator. Replace at the first sign of failure to prevent damage to connected components and maintain vehicle reliability and uptime.

Not sure if this fits your truck? Provide your VIN and we'll verify compatibility before you order.

What's included: One unit — ready for installation.

Why ZTech: ZTech is a quality aftermarket brand built to match OEM form, fit, and function at a value price point — a smart choice for high-mileage and fleet maintenance.

Installation note: Professional installation recommended. Torque all fasteners to manufacturer specification.

Local to Southern California? Same-day in-store pickup at our Irvine, CA location (ready in 4 hours). Local delivery within 50 miles on orders $1,000+.

Returns: 100% refund on unused items returned in original undamaged packaging within 30 days.

Buying for a fleet? Contact us for volume pricing.

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ZTech Engine Thermostat Volvo VNL/D13 | OEM 21613426
ZTech

ZTech Engine Thermostat Volvo VNL/D13 | 21613426 21412639

$79.99

OEM Part Number: 21613426
Also fits / cross-references: 21412639

Fits: ZTech Engine Thermostat Volvo VNL/D13.

This ZTech part regulates engine temperature by controlling coolant flow to the radiator. Replace at the first sign of failure to prevent damage to connected components and maintain vehicle reliability and uptime.

Not sure if this fits your truck? Provide your VIN and we'll verify compatibility before you order.

What's included: One unit — ready for installation.

Why ZTech: ZTech is a quality aftermarket brand built to match OEM form, fit, and function at a value price point — a smart choice for high-mileage and fleet maintenance.

Installation note: Professional installation recommended. Torque all fasteners to manufacturer specification.

Local to Southern California? Same-day in-store pickup at our Irvine, CA location (ready in 4 hours). Local delivery within 50 miles on orders $1,000+.

Returns: 100% refund on unused items returned in original undamaged packaging within 30 days.

Buying for a fleet? Contact us for volume pricing.

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