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timloewe1

Sprinter diesel overheating issues

My 2006 Mercedes Sprinter diesel is overheating The temperature gauge is climbing and it takes an age to warm up I suspect a defective map thermostat but I'm no expert Could this also be related to the water pump temperature sensor coolant system cooling fan or perhaps even a coolant leak Any insights are greatly appreciated

Summary of the thread

A 2006 Mercedes Sprinter diesel was experiencing overheating issues, with the temperature gauge climbing and the engine taking a long time to warm up. The initial suspicion was a defective map thermostat, but other potential causes included the water pump, temperature sensor, cooling fan, or a coolant leak. After consulting with a workshop, it was confirmed that the map thermostat was defective, and replacing it resolved the overheating problem.

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4 comment(s)

johnbaumann4

That does sound concerning The symptoms you describe are indeed indicative of a thermostat issue though other components in the coolant system could contribute While your mileage is relatively low for a vehicle of that age time can still degrade rubber and plastic parts I had a similar problem with my Ford Focus albeit with a petrol engine The engine took ages to warm up and occasionally ran hot I initially suspected the water pump but a diagnostic check revealed a faulty temperature sensor Have you performed any diagnostic checks to read error codes from the ECU This could help pinpoint the source of the problem more accurately It might be worth checking the cooling fan operation too Ensure it kicks in when the engine temperature rises beyond the normal operating range If the fan isn't working correctly it could exacerbate overheating issues

timloewe1 (community.author)

Thank you for the detailed response Regarding diagnostic checks I haven't performed any yet I was hoping to get some informed opinions before potentially wasting money on unnecessary tests You mentioned a temperature sensor issue in your Ford Focus Was the sensor faulty or was there an underlying problem causing it to report incorrect readings Also how did you eventually resolve the overheating issue

johnbaumann4

In my case the temperature sensor itself was defective causing it to send erroneous data to the ECU which in turn affected the cooling fan operation and fuel mixture It's certainly possible that a faulty sensor is the root cause of your overheating problem However given that your engine is also slow to warm up I would still lean towards a thermostat issue The thermostat regulates coolant flow to maintain optimal engine temperature A defective thermostat can either remain open causing the engine to run cool or remain closed causing overheating While you can attempt to diagnose the problem yourself with a multimeter and wiring diagrams I would advise seeking assistance from a qualified technician Given the potential for further damage to the engine it's best to have a professional examine the cooling system thoroughly They can perform pressure tests check the water pump and inspect the thermostat housing for leaks

timloewe1 (community.author)

I appreciate your advice I've decided to take it to a trusted workshop They confirmed the map thermostat was defective and replaced it for 35000€ The engine now reaches operating temperature quickly and the overheating issue is resolved Thank you again for your help

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MERCEDES

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SPRINTER