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Restoring an M Roadster Back to New Condition

Over the last 15-plus years I’ve had the pleasure of owning and restoring a variety of S52 M Roadsters. Some have had as little as 3,000 miles and needed nothing more than diagnosing and fixing a faulty seat harness. Others have required a very lengthy and comprehensive overhaul to address a leaking transmission and differential, dry hoses, frozen brake pistons, loose seat rails, rattling glove box, etc.

No matter the miles and the condition, what has proven to be true time and time again is that the M Roadster’s S52 engine and drivetrain are remarkably durable, straightforward to maintain and in most cases can be restored to perform back to near new running condition through some basic service and maintenance. Regardless of if you currently own one of these cars or if you’re thinking about buying one, you can either address items one at a time as your schedule and budget allows, or you can tackle everything all at once since many of the services overlap and you could save on labor. Either approach can potentially require an extensive amount of time and funds to be performed properly, so it’s understandable that many owners hesitate to take the leap, especially if they are having to pay their shop to perform the service at an average hourly rate of $125 or more.

To shed more light on where to start and the benefits and the costs, I’ll use the example of the recent restoration of a 1998 Estoril Blue M Roadster which I undertook this spring. This car was serviced and restored over a two-month period and required a combined investment of roughly 80+ hours of labor, which I performed over several weekends. Remember, you don’t have to tackle everything at once and you can chip away at items as you have time.

The car I restored has had two owners, the latest one owning the car since the year 2000 and averaging about 3,000 miles a year. The car was adult owned and used for driving around town and always garaged indoors. Once a year it would receive it’s annual maintenance service and a detail. With just under 60k miles on the clock, the car presented well, but it did need a refresh. The most immediate issues with the car were old brake fluid, a bad thermostat, blown seat bushings and a soft suspension. These are not uncommon issues with a car that’s 18 years old and hasn’t been driven much. But most importantly, the car was in good overall condition, completely stock with no accident history or major cosmetic issues.

After driving the car for nearly 500 miles, I had a good idea of what the car needed. I’ve listed most of the issues below, along with the service performed to address each one.

Issue: Dome light wouldn’t turnoff and factory alarm system wouldn't function. The driver’s door wouldn’t always close tight on the first try.
Solution: Replaced the driver’s side door striker, which addressed all three issues. This job can easily take 2-3 hours of labor due to how the striker wiring is connected to the car under the carpeting behind the driver’s seat. Some plastic panels need to be loosened or removed to gain access.

Issue: Both seats rocked back and forth during acceleration and braking.
Solution: Replaced seat bushings on both seats, which addressed this issue. Fixing this problem requires removing the seats from the car by removing the four bolts, disconnecting the seatbelt bolt, then unplugging the 3-4 wiring harnesses from underneath. Once the seats are out, the seat rails are removed from the bottom of the seats to access the damaged bushings. From start to finish this job takes an average of 2-3 hours to perform for both sides.

Issue: Engine has trouble reaching operating temperature at higher elevation or in cold weather.
Solution: Replaced thermostat, water pump and coolant. The thermostat was broken and stayed open, not allowing the engine to reach normal operating temperature. The previous owner had serviced the coolant recently, but I replaced it just to be safe. The water pump was in perfect condition, but most likely original so it was replaced. Both the existing and replacement unit had metal impellers. Total labor is 2-3 hours, and maybe more depending on how long it takes to bleed the system.

Issue: Squeaking noise from front of engine, especially at idle.
Solution: Replaced three belt rollers and the main and accessory belts.  This solved the squeaking problem. It’s best to perform this service while also replacing the water pump and thermostat. Total labor is about 2 hours.

Issue: Car rides soft and doesn’t handle rough roads well. The body squats under hard acceleration.
Solution: Replace stock suspension with Bilstein struts and shocks. Replace control arm bushings.  Also, upgrade stock springs to H&R units to improve handling and slightly lower car, improving its look. As a result, the car’s ride and handling are vastly improved. While performing this job, it’s also a good idea to upgrade the rear shock tower mounts, as they are prone to wearing out and popping out. Replacing the front struts requires the use of a spring compressor. Replacing the rear shocks requires accessing the shock tower mounts which are located behind the roll bars, under the interior carpeting just below the rear window. Removing and installing the control arm bushing requires special tools, otherwise this job is very time consuming. Performing these jobs takes 5-6 hours of labor.

Issue: Steering wheel vibrated slightly under braking. Brake squeak from rear during braking.
Solution: Replace all four rotors and pads, which addressed the issue. Upon inspection, front rotors were not warped visibly, but showed signs of uneven wear on surface.  There was also some surface rust around the center hub. Calipers were removed to replace rotors, all components were cleaned to remove brake dust, reassembled and then the brake fluid was flushed. A brake job on these cars typically takes 3+ hours depending how much time you want to invest cleaning parts. A proper brake fluid flush, including removing fluid from the brake reservoir, takes less than an hour if the wheels are already off.

Issue: Slight oil seepage from transmission. Not dripping, but noticeable oil residue when inspecting the car from underneath.
Solution: Identified the source of the leak at the transmission shaft seal (located at the top rear end of transmission). The seal is only $5, but the labor involved in replacing it can be very costly. This job can be done without having to remove the transmission from the car; however it requires extensive experience and patience, especially because properly removing the seal can be very difficult from underneath the car. Because this car had the original clutch, I decided to remove the transmission and perform a clutch service while also replacing the shaft seal. This is also a good time to replace the drive shaft flex disc, which had cracks on this car. The transmission mounts and driveshaft flex disc should also be replaced if showing signs of wear. Once the transmission was back on the car and installed, I performed a transmission fluid flush. The clutch service easily consumes 7-8 hours and removing the transmission seal can add another 1-2 hours depending on how easily the seal is removed.

Issue: Drivetrain feels a little sloppy or loose under spirited driving. It could be more responsive.
Solution: Replaced engine mounts, driveshaft flex disc (performed while transmission was out), and the shifter linkage/mechanism components. The difference was very noticeable and immediately the car felt much more connected and precise under acceleration. The engine mounts can take 1-3 hours to unbolt, wrestle out and replace. The driveshaft flex disc by itself can be replaced in an hour. The shifter mechanism linkage can only be replaced with the transmission out and requires about half an hour of labor.

Issue: Engine noise from front of engine at 3k rpm or higher.
Solution: Rebuilt VANOS system by replacing the VANOS seal, bearing ring, and the VANOS diaphragm. As a result, the engine was noticeably quieter and felt more responsive. This procedure requires special tools and the cooling system will need to be purged once done, as some of the hoses need to be disconnected. A realistic labor estimate is 8-10 hours, depending how easily you can lock in the cams once the engine is at top dead center. Also, while the valve cover is out, you might as well replace the valve cover gasket and possibly the spark plugs as well. For this car, it was also an opportunity to further detail the hard to reach places in the engine bay.

Issue: Original rear plastic window is foggy and starting to show cracks on corners.
Solution: Replaced rear window with new unit. Total labor is easily 2 hours, but could be less with a second body to help. This requires a lot of patience and some finesse to complete correctly.

Last, but not least, the car received a professional detail to make it look new again. While I could have performed the detail myself using my rotary buffer and my increasing inventory of detail products, I opted to have a professional perform the detail so that they could also treat the plastic headlights and taillights, which can get foggy after a few years. They also thoroughly cleaned and detailed the engine bay, wheels, wheels wells, door hinges and the interior. By having the plastic parts, leather surfaces and paint surfaces cleaned and sealed, the car will not only look like new again, but it will also be protected from the elements for at least a year, if not more.

In the end, with some investment of time and money, these very unique BMW Motorsport cars can be brought back to near new condition and enjoyed for years to come.

Daniel N.


Michael Williams
Monday, June 6, 2016 9:09:47 PM

Looks great. I've got to tackle some of those same issues in a similar car. Thanks for the tips and incredible web site!

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Jon Martin
Fort Collins, CO