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Renault Master Overheating Issue

Hi, I'm hoping someone can offer some insight. I'm having an issue with my 2007 Renault Master diesel. Recently, the engine's been overheating, and the check engine light keeps popping on. I've noticed it seems to happen mostly in stop-and-go traffic. I took a look and the radiator fan isn't kicking in. I've checked the fan itself by hotwiring it to the battery, and it spins, so the motor isn't dead. I suspected the thermal switch, but I'm getting a reading from it. Could it be the speed sensor causing this? The van has 161363 km on the clock. Has anyone experienced this before?

4 comment(s)

Whoa, sounds familiar! I had almost the exact same thing happen last year with my old Vauxhall Astra – overheating in traffic, engine light blazing. Fan wouldn't spin either. Like a broken heart that keeps on beatin' but just won't listen! You say you checked the thermal switch… how did you check it? With a multimeter? 'Cause those things can be sneaky. Sometimes they read okay when they're cold, but flake out when they get hot. Is the fan making any weird noises before it completely gives up?

Good point about the thermal switch. Yes, I used a multimeter, but only when the engine was cold. I didn't think about checking it when hot. The fan isn't making any strange noises at all; it's completely silent, which makes me think it isn't getting the signal to kick in. You mentioned your Astra did something similar. What ended up being the cause in your case?

Aha! Symptoms sound like you are chasing the same gremlin. It turned out to be a faulty speed sensor. The ECU (engine control unit) needs that signal to tell the fan to kick in, especially at low speeds. I spent ages troubleshooting it! Honestly, save yourself the headache and get it to a workshop. They'll have proper diagnostic tools to confirm it and replace the sensor. It might be cheaper in the long run than buying a bunch of parts you don't need. BTW: I would call this 'symptom' a 'canary in a coal mine'.

Thanks a lot for the advice! Sounds like the speed sensor is the most likely culprit. I'll take your advice and get it to a workshop to get properly diagnosed. Turns out it was indeed a defective speed sensor. They replaced it, and the total repair cost was 250€. No more overheating! Thanks again; you saved me a lot of time and frustration.

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