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Video | Will the Cheapest BMW M5 Ever Be Finished? A Bottomless Pit of Repairs

When I bought a very broken 2007 BMW M5 for only $6,500, I knew it was going to be a challenge to get back on the road, but I didn’t think it would be this bad. After nearly doubling my purchase price in parts and repairs, my mechanic, the Car Wizard, cannot wizard his way out of this basket case — and he has given up. So my first drive post-Wizard consisted of bringing my still very broken M5 from one repair shop to another — and I can’t help but question whether this car was worth dealing with in the first place.

The first red flag was buying it from a Honda dealer, who took the M5 on trade and was desperate to get rid it for well under wholesale value. Obviously, if someone is switching from a 500-horsepower European super-sedan to any kind of Honda, it’s going to be for a very good reason. A failing transmission, which has a dealer replacement cost of well over $10,000 — along with enough strobing dashboard warning lights to induce a seizure — is certainly a good reason. My mechanic estimated to take care of all the issues, and going with a used transmission if needed, would cost $8,000 to $11,000. For some stupid reason, I thought it would be a good idea to start fixing it anyway, but as we got started on the repairs, there was actually some reason for optimism.

The first lucky break was finding a complete used, low mileage SMG transmission, along with an oil cooler to fix the massive oil leak, for only $2,700. This took all of the guesswork out of fixing whatever was causing problems on the transmission, which would have involved throwing on a bunch of random expensive parts, blindly hoping it would solve the issue. Having everything from a working wrecked car made things much simpler. Another major savings came after a good result from an oil analysis, which didn’t detect any evidence of copper in the oil from worn rod bearings. This meant I didn’t need to have the engine torn apart for this expensive preventive repair anytime soon.

Installation of the transmission and oil cooler went well, with the only surprise being a randomly failing air conditioning condenser — and with the car up on the lift, I was able to shift through the gears easily. Unfortunately, just touching the brittle plastic paddle shifter to downshift the transmission broke it off from the steering wheel — but the wizard was able to glue that back together. After buttoning up everything up underneath the car, we were finally able to take in on a test drive, and everything seemed great — at first.

For normal cruising, the M5 drives really well. Gone is the jerking transmission, and the dazzling array of warning lights, as the V10 engine burbles along. Unfortunately, though, nobody buys a 500-hp M5 to drive it like they are transporting someone home after hernia operation — and the moment I try to use this super-saloon as intended, things go horribly wrong.

Despite a redline of over 8,000 rpm, my M5 acts like it hits a wall at 4,500, bonging in anger as warning lights begin littering the dashboard — and the engine immediately goes into limp mode. Turning the car off and on again returns the car to normal operation — but if I dare rev it above the middle of my tachometer, the computer backhands me in the face every time.

Unfortunately, the Car Wizard doesn’t have the ability with his scan tool to look deep inside the M5’s engine computer to figure out what’s happening. He’s only able to see some vague codes referring to communication errors with the crank sensor, along with misfires, which could be caused by a number of different things. Since he doesn’t want to guess at fixing the problem with very expensive parts, the Car Wizard has suggested I take it to a BMW specialist for a more in depth diagnosis. This is the first time I’ve ever seen him admit defeat.

Thankfully, I know a BMW specialist, who also owns an M5 like mine — but even with the proper BMW scan tool, he’s still not sure exactly what’s causing it. Tomorrow, he will try installing new crank sensor, which is a cheap part — and if that doesn’t solve the problem, he suggested doing the spark plugs and coils. From there, things get very expensive, with possible issues ranging from clogged catalytic converters to bad throttle actuators — or maybe even a bent disc on the flywheel. This part gives the crankshaft sensor readings for the engine revolutions — and if that’s the problem, poor Car Wizard will have to pull the transmission again to replace the flywheel.

For those thinking this project obviously isn’t worth the trouble, I’m not quite ready to agree with you yet. 500 horsepower is still a very impressive figure for a sports sedan, and the styling of this beautifully flared body and interior has aged really well. I tend to bash BMW reliability a lot, but a 10-year-old Audi S6 and Mercedes-Benz E63 AMG has their fair share of very expensive common failures as well. If I didn’t buy the cheapest, and often worst examples of these cars, my ownership experience would probably be a lot more positive.

So far, I’ve spent $4,516 in repairs, bringing my total investment with the purchase price to a little over $11,000. Most M5 examples on Autotrader with similar mileage to mine are listed between $13,000 and $15,000 — so I still have a few thousand to spend before I’m upside down on my "investment." Unfortunately, that’s not much of a cushion considering the expensive cost of M5 parts — so there’s a very good chance I’ll end up losing badly. Unlike a gambling problem though, at least I’ll have something to show for it at the end: A shiny, red, M-badged monument to my stupidity.

MORE FROM OVERSTEER:
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