Reische Performance FORD-4D 170° Performance Thermostat

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Reische Performance FORD-4D 170° Performance Thermostat
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The Ford-4D thermostat is hand assembled from components made by your OEM supplier. It also has the same size diaphragm and proper bypass control so you are guaranteed maximum efficiency from your cooling system. 100% made in USA.

Whether you are using an aftermarket radiator or not, this thermostat will provide the best possible heat dissipation from your setup and even deliver better overall performance than our competitor's 160° thermostats. Reische believes the 170° opening temp is the ideal balance for high performance engines, providing high flow to your radiator by mid-180 temps along with good all season performance. With proper fan settings your coolant temps in cool weather will be in the 170s and in hot weather the 180s, giving those running high levels of timing and/or boost added protection against engine-damaging detonation as well as maximum hp.

All Reische Performance thermostats ship with a new O-ring and are backed by a 5 YEAR WARRANTY.


05-06 Mustang 4.6L

96-98 Cobra 

99-04 Cobra/Mach1


Fan ECT1 High On: 190°
Fan ECT2 High On: 190°
Fan High Off: 186°
Fan Low Off: 182° (shuts off @180°)
Fan Low On: 184°

Low Fan Speed: 186° (shuts off @178°)
High Fan Speed: 190°

Ideally the fan settings in your tune should be lowered to see the best possible heat dissipation from your cooling system. Otherwise a low temp thermostat will only be effective when the vehicle is moving because heat cannot be removed unless there is air passing through the radiator. However, there is not a handheld programmer available at this time capable of modifying fan settings in most of the new Ford engine management systems. The fan speed tables will need to be adjusted through a custom tune (available through Lethal Performance) or via tuning software. These new systems estimate coolant temps based on readings from a dry head temp sensor. However these ‘inferred’ ECT values can be more volatile and may read as much as 8-10° hotter than actual coolant temps. This means that a vehicle using our 170° thermostat could see ECT anywhere between 165-205°, depending upon conditions and fan settings. We rely on your feedback, so please let us know if you become aware of any new developments in managing the fan settings for these applications.

More Information
Condition New
Warranty 5 Years
Manufacturer Reische Performance
Manufacturer Part No RP-FORD-4D
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