Sierra 18-2587 Transmission Oil Cooler, Replaces Mercruiser 99356A2 Power Steering Cooler

The Sierra 18-2587 is a replacement power steering and transmission oil cooler built for Mercruiser applications, directly replacing Mercruiser part number 99356A2. It is designed to dissipate heat from power steering fluid circulating through the system, with a rated capacity of 4 GPM maximum for power steering fluid and 25 GPM maximum for the raw water side that cools it.

The cooler features a 6 inch tube bundle with an overall length of 8 inches, and a water inlet and outlet sized at 1 1/4 inches (31.8mm) to match standard hose fittings. It ships bare metal with a machined exterior finish, leaving it ready for the installer to apply primer and factory paint to match the surrounding engine components.

This cooler is intended as a direct fit replacement wherever the original Mercruiser 99356A2 power steering cooler is specified, making it a straightforward swap for a failed or corroded factory unit.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2587
• Product Type: Transmission Oil Cooler / Power Steering Cooler
• Replaces (OEM): Mercruiser 99356A2
• Water Inlet/Outlet: 1 1/4 inches (31.8mm)
• Tube Bundle Length: 6 inches
• Overall Length: 8 inches
• Power Steering Fluid Flow Rate: 4 GPM maximum
• Water Flow Rate: 25 GPM maximum
• Finish: Bare metal, machined, ready for primer and factory paint
• Weight: 1.37 pounds
• UPC: 808282243630

Fitment

Designed as a replacement power steering cooler for Mercruiser applications.

Replaces (OEM)

• Mercruiser 99356A2

Frequently Asked Questions

What does the Sierra 18-2587 replace? The Sierra 18-2587 replaces the Mercruiser power steering cooler with OEM part number 99356A2, making it a direct swap for that factory part.

What is the overall length of this cooler? The Sierra 18-2587 has an overall length of 8 inches, built around a 6 inch tube bundle.

What size are the water inlet and outlet? The water inlet and outlet on the Sierra 18-2587 are sized at 1 1/4 inches, or 31.8mm.

What flow rates is this cooler rated for? It is rated for a maximum of 4 GPM of power steering fluid and a maximum of 25 GPM of water flow on the cooling side.

Does the Sierra 18-2587 come painted? No, it ships bare metal with a machined exterior finish, ready for the installer to apply primer and factory paint to match the engine.

How much does the Sierra 18-2587 weigh? The Sierra 18-2587 transmission oil cooler weighs 1.37 pounds.

Is this a power steering cooler or a transmission cooler? It functions as a power steering cooler for Mercruiser applications, cooling power steering fluid using raw water flow through the tube bundle.

Will this fit my Mercruiser? The Sierra 18-2587 is built as a replacement for the Mercruiser 99356A2 power steering cooler, so it fits wherever that original part is specified.

What is the UPC for this part? The UPC for the Sierra 18-2587 transmission oil cooler is 808282243630.

Is the Sierra 18-2587 an OEM or aftermarket part? It is a Sierra-branded aftermarket replacement engineered to match the fit and function of the OEM Mercruiser 99356A2 power steering cooler.