Owners' Troubles: The N63 BMW Thermostat Leak Debacle and How to Sidestep a $6k Repair Nightmare

You know, there's something truly special about the sensation of sliding into the driver's seat of a meticulously engineered machine. The purr of the engine, the delicate balance of power and precision — it's a symphony of man and machine in perfect harmony.

But what happens when that harmony turns into a cacophony?

Enter the 2017 N63-powered BMW G11 750i xDrive.

Sleek, powerful, and, on the surface, the epitome of German engineering. Yet, as with many complex masterpieces, there are sometimes flaws that lurk beneath the surface.

Imagine the surprise of our customer when they tried to awaken the beast within this N63, only to be met with a defiant "Drivetrain Malfunction: you can continue driving" message.

It's akin to Beethoven's Symphony No. 9 suddenly going mute right before the crescendo.

The audacity! And, as if the sting of a non-compliant engine wasn't enough, there's the small matter of the car's inconvenient position in the middle of our parking lot, thanks to our ever-so-thoughtful tow truck driver.

Now, I have my qualms with post-2010 BMWs — and don't get me started on the lack of an emergency neutral release for the automatic transmission. But this was a puzzle that piqued my interest.

But I digress.

With my trusty ICOM Next in hand, I dove into the labyrinth of the BMW's electronic brain. What emerged was a tale of a characteristic map thermostat, a sneaky leak, and a trail of coolant with a penchant for destruction.

But fear not, dear reader.

For every problem, there's a solution (or in this case, a deep dive into the inner workings of a modern marvel gone awry). So, strap in, and let's journey together into the world of the N63, its quirks, and the remedies to keep it purring. Because while a $6k repair bill might be a hard pill to swallow, knowledge? That's priceless.

What Happened?

As our reluctant 750i took center stage, the ISTA did its rendition of a medical scan, peering into the G11's very soul.

And like a seasoned physician, it confirmed the grim diagnosis: the right DME module was giving us the silent treatment.

Now, with any other BMW, my instinct would guide me towards a routine check of the voltage supply and PT-CAN.

But there's nothing 'routine' about this situation.

You see, the N63 and I, we share some history. It's like an old jazz tune you've heard a thousand times — you know exactly when the saxophone's going to hit that high note. The N63's unique "characteristic map thermostat" is its signature solo, and in this case, it played a discordant note.

Imagine a dam with a tiny leak. Over time, that leak can flood entire landscapes. Similarly, our thermostat's inconspicuous leakage was enough to send coolant coursing through the engine wiring, right up to the DME.

And the finale? A silent DME, robbed of its ability to sing.

But one mustn't jump to conclusions.

A good maestro never blames his instrument without a thorough examination.

So, with a sense of grim anticipation, I delved into the DME's connectors. What greeted me was the aftermath of a silent war: the corrosion, the haunting blue of coolant traces, the telltale signs of a burned connector and its fallen pins.

It was a scene straight out of a crime novel (photo evidence provided below, for the curious).

Yet, hope springs eternal.

With the N63's unique duality — two identical DMEs, each governing a bank of cylinders — there's an opportunity. A quick swap, post a cleanup act, was all it took to confirm our suspicions. Alas, the DME had sung its last note.

It was time for an encore, but with a brand-new star.

In Their Own Words: BMW's Official Stance on the N63 Dilemma

Ah, the illustrious service bulletins — the official scrolls from the automotive gods. It's the company's way of saying, "We heard you, we see the issue, and here's our take."

So, what does BMW have to say about our dear N63's muted performance? Let's unravel the mysteries of their official directive.

In a revised service bulletin, dated July 2016, titled "N63R Map Thermostat Faults", BMW acknowledges the issue, and here's a distilled rundown:

The Situation:

Our beloved 'Service Engine Soon' light might shine bright with an array of fault codes, ranging from a clamped thermostat to short circuits and even alarming messages like "Engine too hot! Drive gently." The most severe of symptoms? A complete radio silence from the DME, akin to a maestro turning his back to the orchestra.

The Culprit:

It seems the N63's map thermostat is a tad leaky, letting coolant slip past its electrical connector. It's like a secret passage for coolant, leading straight to the heart of the engine's electronics.

The Remedy:

BMW's approach? If it's contaminated, replace it. Simple as that. Here's a step-by-step:

1. Inspect the Map Thermostat: If there's coolant present in the engine wiring sensor harness for cylinders 1-4, the map sensor thermostat and the sensor harness need replacing.
2. Investigate the DME: If there's no coolant at the DME's harness connector, then all's well. If there is, the journey continues.
3. Deep Dive into the DME and PDM: If any of these connectors show signs of contamination, it's time to ring up the big guns at the TC DME group for parts replacement approval.

Oh, and a word to the wise: when getting a new thermostat, ensure it's of the improved version with an index number of "05" or later. Anything less, and you're back to square one.

The Logistics:

BMW graciously covers this under their New Vehicle Limited Warranty for Passenger Cars and Light Trucks or the BMW Certified Pre-Owned Program. And for those intrigued by the nitty-gritty, there are specific labor operations, part numbers, and even procedures for potential overlapping labor.

In essence, BMW's acknowledgment and the accompanying action plan serve as a testament to their commitment to their machines and the people who adore them. The maestro may have momentarily turned his back, but the symphony goes on!

Rising from the Ashes: Resurrecting the 750i

Ah, the grand return to our protagonist, the pristine white 750i. It's like returning to a riveting book, eager to see how our hero fares after facing adversity. So, where did our journey with the 750i lead us?

Diving deep into the digital realm of ISTA, the diagnosis was clear. Our Bimmer needed a heart transplant (or in automotive terms, a new DME module), a new PDM module (that's the power distribution module for the uninitiated), and a revamped engine wiring for cylinders 1-4.

But as with any epic saga, there were surprises along the way.

You see, the PDM, the very hub that powers the N63's sensors and actuators, had a connector that was not just damaged but scorched to a crisp. The kind of damage that tells tales of battles fought and lost. It was so melded, so fused that I had to resort to a bit of brute force, cracking open the PDM's armor to free the captive connector.

Now, you might wonder, "Why the theatrics for a part destined for replacement?" Well, sometimes, sheer curiosity drives one to see the extent of the devastation. And as evidence, behold the photo below of the connector, a molten mess reminiscent of a phoenix's fiery end.

With the autopsy complete, the real work began. A dance of wires, modules, and connectors ensued, lasting a day and a half. The car's nervous system rewired, its new DME and PDM installed, it was time for the final act — the software ritual.

For these modules to sing in harmony, they needed to be on the same 'I-Level' (or software version, for those less versed in BMW's lingua franca). Though this process spans nearly a full day, it's a passive wait, akin to watching clouds drift by, as bytes of data soar through the ether.

And after a bill that would make one's wallet weep to the tune of $6k, our white knight, the 750i, was reborn.

The engine, once silenced, now purrs with renewed vigor, ready to serenade the open roads once more.

An Enthusiast's Tale: A Customer's Journey to My Shop

In this dance of diagnostics and repairs, sometimes the most telling tales come not from the metal and circuits of the car, but from the people who drive them.

Enter our customer: a first-timer at my shop.

But within minutes, it was evident. This wasn't just any car owner; this was an enthusiast, someone for whom every rev of the engine tells a story, every purr resonates with emotion.

Naturally, I probed a little.

Were there any whispers, any inklings, before the 750i decided to play hard to get?

Because you see, from experience, a thermostat issue doesn't always spell doom for the DME or PDM — at least not immediately.

It's like a slow simmer, one that gradually reaches a boiling point. And this car had clearly been simmering.

His response?

A solitary check engine light, about a month prior. Seems harmless enough, right? He did what any responsible car owner would do — scheduled a service appointment. But alas, the world of car servicing can sometimes move at a glacial pace.

Two weeks!

That was the wait time just for a diagnosis.

And the diagnosis?

The thermostat, the very heart of our tale, needed a replacement.

But the saga of waiting wasn't over. Another two weeks loomed before the surgery could occur. In an interim agreement, he decided to take the car back, with plans to return for the procedure later.

But, as they say, life and 750is are full of surprises. Merely days before the scheduled repair, our 750i decided to take an unscheduled hiatus, right in the middle of a mall parking lot. A shopping trip turned into a vehicular melodrama.

And that's how our protagonist, the white 750i, landed at my doorstep. A tale of warnings ignored, delays, and an enthusiast's love for his car. The rest, as you've journeyed with me, is automotive history.

Here's the actual thermostat and the connector: