My transmission cooler, which is integral to the main coolant radiator, developed a leak about 6 months ago. I couldn't stump up for a new rad at the time so I fitted an aftermarket external transmission cooler up behind the front grill. Since then my gauge stays closer to a 1/4 rather than up at 1/2. It fluctuates a lot depending on the driving, going vertical on big climbs, but then dropping down. Is the transmission oil temp important to the equation or is this a thermostat issue. All received wisdom welcome! I can borrow a laser thermometer, I also have an OBD reader. I'm unclear what to point it at to get the readings to test the thermostat other than the intake hose, where do I go for the second reading, will the ODB give me the second, i.e. where is the the temp sensor in the flow sequence?
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