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juliuslehmann1

BMW 4 Series Diesel Overheating & Limp Mode Crisis Alert

Coolant level low

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Check engine light on

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Overheating

Hey all! Having trouble with my 2017 BMW 4 Series diesel (154k km). The engine's running hot, gone into limp mode, and throwing multiple warning lights. There's coolant leaking and I suspect it might be a control module issue. My last mechanic visit wasn't great, so I'm looking for advice. Has anyone dealt with similar symptoms? What was the actual problem and did you find a reliable mechanic to fix it? Thanks in advance for any help!

4 comment(s)


felixfuchs3

Had a similar issue with my 2014 BMW 5 Series diesel last winter. Started with the same symptoms, limp mode, warning lights, and coolant leak. Turned out the control module's cable connection was corroded, causing faulty readings and system malfunctions. Found a good specialist who diagnosed it properly. The coolant leak was actually coming from where the control module connects to the cooling system, the connection had deteriorated. The mechanic replaced the wiring harness and cleaned up the corroded pins. Not a massive repair, but definitely needed expert attention to diagnose correctly. Would suggest getting it checked soon though, these symptoms can lead to bigger problems if left unchecked. My car's running smooth since the fix, no issues in the past 8 months. Just make sure whoever looks at it knows BMW diesel systems well. My previous mechanic missed this entirely and kept replacing other parts.

juliuslehmann1 (Author)

Thanks for sharing your experience! That's really helpful as I'm facing these exact same symptoms. The specialist you found seems to have nailed the diagnosis. Quick question, do you remember roughly how much you ended up paying for the repair? Also, has everything stayed completely problem-free since the fix, or have you noticed any other small issues pop up? Just want to know what I might be looking at cost-wise and if I should expect any follow-up problems.

felixfuchs3

Hey there! Happy to give you an update. The repair ended up costing 95 € to fix the cable connection, pretty reasonable considering how much trouble it was causing. The mechanic found the control unit communication error and sorted it right out. And you'll be glad to hear that since getting it fixed, my BMW's been running like a dream! No more warning lights, no limp mode, and definitely no more coolant issues. It's honestly such a relief after all that hassle. Makes me wish I'd found this mechanic sooner instead of wasting time with the first guy who couldn't spot the problem. I know BMWs can be tricky, but seems like this was one of those cases where it was a relatively straightforward fix once you get the right mechanic looking at it. Really glad I could help point you in the right direction with this one. Haven't had a single issue pop up since the repair, and it's been great to get back to enjoying the car without worrying about every little noise or light on the dash. Hope you get yours sorted just as easily!

juliuslehmann1 (Author)

Just got back from the mechanic and wanted to update you all! Took my BMW to a specialist who diagnosed the exact same issue you mentioned, corroded control module connections. Got it fixed today and the total came to around 110 €. Bit more than what you paid, but still way better than what I was fearing. The whole experience was night and day compared to my last mechanic. This guy knew exactly what he was looking for after I described the symptoms. Opened everything up, showed me the corroded bits, and explained the whole repair process. Really appreciated the transparency. Car's running perfectly now, no warning lights, engine temperature's normal, and that worrying coolant leak is gone. Took it for a good test drive and it feels like new. Thanks so much for the advice, you really helped me avoid what could've been an expensive wild goose chase with the wrong mechanic!

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