BMW, Porsche, Mini, Mercedes-Benz, Volkswagen, Audi. You’re probably familiar with these brands, but how familiar are you with their parts?

European vehicles need repairs just as often as American or Asian vehicles, if not more often. They also boast an extremely strong following among tuning enthusiasts. You’re almost guaranteed to find modified VWs, Audis and BMWs at just about any car show or meet you pull up to.

So, what is it that sets these vehicles apart from the rest? Let’s take a look at what makes these vehicles so desirable to owners, and what we as parts pros need to know in order to help them buy the right parts for their needs.

German Engineering

Yes, that’s a reference to Volkswagen’s advertising campaign from the mid-2000s. These commercials capitalized on the popularity of automotive TV shows like “Pimp My Ride” and “Overhaulin.” They were cheesy, over the top and downright funny.

All jokes aside, there’s something special about the phrase “German engineering.” German automakers have long led the industry with pioneering and innovative technology. The Benz Patent-Motorwagen (“patent motorcar”) was built in 1885 by the German Carl Benz, so you could say that cars were invented by the Germans – but it didn’t end there. Nearly every modern automotive system has been influenced or refined by German engineering and innovation: everything from seat belts to air bags, adaptive cruise control to antilock brakes and traction/stability control. The list goes on and on.

There’s another trait that I associate with German engineering (and all European vehicles), but it comes in the form of an expression: “10 pounds of stuff in a 5-pound bag.” While it seems that cars aren’t getting any bigger, automakers are finding ways to fit more and more systems, parts and control modules into them than ever before.

If you’ve ever looked under the hood of an Audi S6 or S7 with the 4-liter turbocharged V-8 engine (pictured above), you’ll know what I’m talking about. These engines don’t look like any other V-8 engine in the world, and they’re a good example of how creative automakers have to be in order to fit their powerplants into modern vehicles.

Complexity

There are, of course, a few drawbacks to this sort of innovation and creativity: namely, complexity. Complex systems tend to utilize more individual parts, and this means that they may be more vulnerable to part failures. What we mean by this is the more hoses, pipes or connectors automakers add to vehicles, the more likely it is that any of these parts could leak or fail and need to be replaced.

Let’s look at an example of this complexity: the cooling circuit from an S55-powered BMW M3 or M4 (Fig. 1). This diagram shows the number of hoses, pipes and heat exchangers that are needed to cool the engine, the incoming charge air and the engine oil. While this system is designed to hold up to a lot of abuse, a single faulty connection or leaking hose could cause a breakdown.

Lightweight Materials

Plastics and composite parts are replacing steel and aluminum parts in the interest of weight savings and fuel economy. Unfortunately, this sometimes comes at the cost of durability. The turbocharged 1.8-liter and 2-liter engines found in modern VWs and Audis feature radiator hoses with plastic connectors on either end. These connectors are known to become brittle and crack after years of heat-cycling under the hood. You might find that the lower radiator hose on these same engines has a coolant-temperature sensor built into the connector in the interest of saving space.

Plastic isn’t the only lightweight material being used by modern automakers. The bolts that secure the thermostat to the water pump on the N54-powered BMW 335i are aluminum and cannot be reused once they’re removed. Aluminum bolts also are used to secure the transmission pan on the Mercedes-Benz 722.9 seven-speed automatic transmission.

As parts professionals, it’s our responsibility to always “sell the whole job” to our customers. If a customer comes in for a radiator because the original one cracked, you should suggest that they replace other parts such as the hoses, since they may be just as brittle as that radiator was when it failed. If your customer is replacing a component that’s secured with aluminum bolts or hardware, be sure to sell it to them so they have everything they need before they start the repair.

Remove and Discard

Let’s dive deeper into hardware, because it’s especially important on European vehicles. Torque-to-yield (TTY) fasteners are far more common on these applications, used everywhere from suspension points to drivetrain mounts, and everything in between. TTY fasteners are torqued to extremely high values. This literally causes the bolts to stretch nearly to the breaking point, but in exchange it’s able to apply the maximum clamping force possible. Since these bolts are stretched out when torqued, they should not be reinstalled, as they could snap when tightened.

Fasteners with locking splines or nylon locking rings, or pre-applied threadlocking compounds, help to prevent them from loosening. These types of fasteners are rather common in European applications, and most cannot be reused once installed.

It’s always a good idea to check your parts catalog for suggested hardware, and then pass that information to your customer. If you come across a repair in which you needed to replace the hardware, share that experience with your co-workers. Sharing your combined experiences will only benefit you, your team and your customers.

Double Vision

I’d like to conclude with a unique example I found while working on a 2017 BMW M4 with the S55 inline-6 engine. The vehicle was in for a boost-tap install so the customer could monitor boost pressure from a gauge mounted in the A/C vent. The boost tap was a billet aluminum spacer that mounted between the MAP sensor and the intake manifold. A hose connected the boost tap to a gauge inside the vehicle. The customer had installed the boost tap, but it was only reading boost pressure, not engine vacuum.

During a visual inspection I quickly spotted the problem: The boost tap had been installed into the wrong location. There are actually two MAP sensors on this engine: One is located on the charge-air cooler on top of the engine, and the other is mounted on top of the intake manifold.

The MAP sensor on top of the intake manifold is almost impossible to see because the charge-air cooler is in the way, but it’s the only one capable of reading engine vacuum since it’s located after the throttle body. This was a quick and easy fix, but it’s a good example of how easy it can be to miss something obvious in such a busy engine compartment.

Redundant sensors can be common in European vehicles like the M4 from this example. So, be sure to ask your customer the right questions and really get to the bottom of what it is that they’re working on, and what they need to fix it right the first time.