VW Bug Exhaust Leak Symptoms

Written by richard rowe
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VW Bug Exhaust Leak Symptoms
(Image by Flickr.com, courtesy of Till Krech)

With its air-cooled cylinders, sturdy boxer construction and over-engineered rotating assembly, it's small wonder the VW Bug is known as one of the most reliable cars ever produced. However, no matter how well built they were from the factory, a fair number of VWs are as old as many of their current owner's grandparents, so it comes as no surprise that maintenance on these machines may be required.

Exhaust System

For having such a simple engine, the VW's exhaust system can be horribly convoluted, offering many opportunities for leakage. Whether designed for stock hatchbacks, minibuses or Baja racers, all VW headers share the same common weakness: they dangle behind and often beneath the car, and thus are constantly inundated with all the water, salt and trash the wheels can kick up.

Exhaust Weaknesses

The average VW Bug tubular exhaust is well supported on all sides, which is good because the welding on some stock and aftermarket exhaust pipes is sub-par at best. The most notoriously weak exhausts are those produced in Mexico, which are known to crack and leak around the collector. GT-style exhaust systems often allow water to enter through straight exhaust tips and become trapped in the bottom of the muffler, rusting it from the inside out.

Muffler Leak

A muffler leak will allow higher frequency sound to exit and will make your VW sound like a smaller displacement engine. This can be differentiated from a leak further up in the system by the fact that the exhaust drone coming through the car is out of proportion to the extra sound emitted.

Collector Leak

This will make your car louder overall. The difference between a collector leak and a muffler leak is that in the case of the collector, the exhaust note sounds essentially the same, but is much louder. In this sort of leak, you may actually be able to feel minute vibrations coming through the floor-pan or steering column.

Primary Leak

Unlike other kinds of leak, this leak occurs on only one cylinder, where the primary tube meets the exhaust port on the head. This type of leak can be distinguished from the others, since only that cylinder will be louder, creating a distinct and rhythmic popping sound that increases with rpm.

Finding the Leak

When you start the car in the morning, dump a glass of soapy water over all the joins and welds in the system, including the pipe-to-collector, pipe-to-muffler and primary-to-head joins. The escaping gases will cause the water to bubble up, making it easy to locate the source of the leak. This should only be done when the engine is cold, however; splashing water on a hot tubular exhaust can damage the system.

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