Four Seasons 91587 HVAC Heater Core

Four Seasons 91587 Heater Core Overview

Four Seasons 91587 is a copper/brass HVAC heater core built for direct-fit replacement in select Ford and Mercury applications. It is engineered to meet or exceed OEM requirements and is sized for the factory heater core location in compatible vehicles.

This heater core is listed for 1977-1978 Lincoln Versailles and 1975-1978 Mercury Monarch with A/C. If you are replacing a leaking or restricted heater core in a Mercury Monarch or Lincoln Versailles, Four Seasons 91587 provides the correct core dimensions and tube sizing for the application.

Key Features

• Copper core material with copper/brass heater core construction
• Meets or exceeds OEM specifications
• Core dimensions: 7-3/4 in. length, 6 in. width, 1-7/8 in. thickness
• Tube sizes: 0.625 in. and 0.625 in.
• Direct replacement HVAC heater core for factory-style service
• Four Seasons Heater Core line for HVAC repair applications

Detailed Product Description

Four Seasons 91587 is a replacement HVAC heater core designed around the original equipment dimensions for select classic Ford-platform vehicles. The copper/brass construction supports efficient heat transfer, while the compact 7.750 in. x 6.000 in. x 1.875 in. core size helps ensure proper fit in the heater case. This part cross-references Anchor 9017 for the same application.

Use Four Seasons 91587 when servicing the heater system on 1977-1978 Lincoln Versailles or 1975-1978 Mercury Monarch, including Mercury Monarch models with A/C. The part number 91587 is also referenced across multiple aftermarket listings, making it easier to match the correct heater core during HVAC repair.

Common Problems This Part Can Address

• Coolant leakage from a damaged heater core
• Weak or uneven cabin heat output
• Restricted coolant flow through the heater circuit
• Fogging or sweet coolant odor inside the cabin
• Corrosion-related heater core failure in the HVAC system

Installation Notes and Tips

Verify the heater core dimensions, tube diameter, and vehicle fitment before installation. Confirm the application for 1977-1978 Lincoln Versailles and 1975-1978 Mercury Monarch, especially Mercury Monarch models with A/C, to ensure the correct HVAC heater core is selected. Inspect hoses, clamps, and the heater case for wear or contamination before reassembly.

Because heater core replacement often requires access through the HVAC housing, take care to drain the cooling system properly and check for leaks after installation. Match the tube orientation and case fit to the original part before final assembly.

Quality Assurance

Four Seasons lists this heater core as meeting or exceeding OEM requirements, supporting OE-style fit and function for the intended applications. The Four Seasons 91587 heater core is built for replacement service in the factory HVAC system and is backed by the brand’s heater core product line standards.