Rein CTN0074 Engine Coolant Thermostat

OE Quality Thermostat Insert for BMW Cooling Systems

The Rein CTN0074 engine coolant thermostat is an OE-quality insert built for precise temperature control and consistent cooling system response. It is a direct-fit solution for select BMW models, including 1985-1993 BMW 325e, 325es, 325i, 325iX, 524td, 528e, 535i, 635CSi, 735i, and 735iL applications.

With a silver finish, included gasket or seal, and an 80-degree start-to-open temperature, this thermostat supports stable engine operating temperature in classic BMW cooling systems. Rein CTN0074 is engineered for fit, calibration, and service life that align with OE expectations.

Key Features

• OE-quality thermostat insert for BMW cooling system service
• Start to open temperature: 80 degrees
• Gasket or seal included for installation
• Silver finish
• Built with high-quality metals and components for durability
• Temperature-calibrated for consistent coolant flow response

Detailed Description

Rein Automotive CTN0074 is an engine coolant thermostat insert designed for direct replacement in select BMW applications. It is produced to meet or exceed OE material standards and is calibrated to respond at the specified opening temperature, helping maintain proper engine temperature control. This part cross-references BMW 11531265085 and 11531710953 for the same application. For drivers and technicians servicing BMW 325i, 535i, or 735i cooling systems, the CTN0074 offers a straightforward OE-style replacement path.

What This Thermostat Helps Address

• Engine running too cool or too warm due to thermostat wear
• Delayed coolant circulation from a sticking thermostat
• Temperature fluctuation during normal driving
• Cooling system service on aging BMW engines
• Replacement of a thermostat insert with degraded sealing surfaces

Installation Notes and Tips

Install the thermostat insert in the correct housing orientation and verify the sealing surface is clean before assembly. Replace the thermostat when servicing the cooling system if the original unit shows signs of sticking, corrosion, or inconsistent temperature control. Confirm vehicle application by year, make, and model before installation. Fits 1987-1993 BMW 325i, N/A; Fits 1986-1993 BMW 535i, N/A; Fits 1986-1992 BMW 735i, N/A; Fits 1988-1992 BMW 735iL, N/A; Fits 1988-1991 BMW 325iX, N/A; Fits 1986-1989 BMW 635CSi, N/A; Fits 1985-1988 BMW 528e, N/A; Fits 1985-1987 BMW 325e, N/A; Fits 1986-1987 BMW 325es, N/A; Fits 1985-1986 BMW 524td, N/A.

Quality Assurance

Rein Automotive positions this thermostat insert as an OE-quality replacement built with durable metals and components and calibrated for precise cooling-system performance. The design focus is consistent fitment, dependable sealing, and service life aligned with original equipment expectations.