Replace the Exhaust System on a 75‐to‐78 VW Bus

If you own a bay window – 1968 to 1979 – VW Bus or camper, a large part of the health of the vehicle, from heating the interior to your engine running smoothly, depends on the health of your exhaust system. For many of those model years, the options are wide and varied, however, for Buses sold in the U.S. for model years 1975-1978, the exhaust system poses a number of problems. The differences with those models and the limited U.S. run and a complicated muffler system combine to make the perfect storm of issues for owners looking to keep their VWs running right. Replacing a shot exhaust is a must. The standard system for performance and everything else unless you are doing serious tuner engine work is the stock system VW originally installed. However, it may be difficult to find several essential pipes for the 75-78 exhaust system.

Steps

  1. Consider what kind of exhaust you have.
  2. Inspect the existing system. Look over your stock system. Is it in good shape or maybe needs something simple, like replacing a hanger or tailpipe? Either leave it alone or do minor repairs. If it is stock, what you have is better than anything on the market.
  3. Place cardboard under rear of vehicle where you will be working. You might be able to do the work without jack stands or ramps. The cardboard will keep any crud that comes off the old system from getting on your driveway while protecting the new system from getting scratched up – scratches through the paint can make it rust faster.
  4. Remove the old system. This may be as simple as removing the bolts at the flanges, then removing the hangar bolts and lowering it to the ground. Some penetrating lubricant on the nuts may help loosen them up. A number of areas are a bit difficult to get to with the old system in place, so don’t be afraid to cut the soon-to-be discarded pipes to make getting at bolt faces easier. Make sure the old exhaust is supported as you unbolt it to keep it from torquing the heat exchangers or anything else it may be attached to.
  5. Now that the old system is gone, take a good look at your heater boxes. Are they in good condition with no dents, major rust or other serious defects? If they are, then go ahead with the installation. But if your boxes are damaged, then replace them with a model that is compatible with replacement stock exhausts and use that exhaust configuration instead.
  6. Look at the flange surfaces for the heater boxes and the new exhaust system. Make sure they are smooth and flat. Crud can build up on the heater box side, especially if there were exhaust leaks through the old gaskets. Also, hold the replacement system in place to make sure the flanges are at least close to meeting up. A quarter inch offset is fine, but some of the kits being mass produced are coming out with flanges that are not even close. These need to be sent back. For minor defects in the mating surfaces of the flanges, either smooth them out yourself or take them to a machine shop and have them do it. Smooth surfaces are essential to preventing exhaust leaks.
  7. While supporting the new exhaust in place, on the end opposite the tail pipe, put the first bolt, with washers, etc, through the exhaust flange, gasket – or two if necessary – and through the heater box flange and hand tighten.
  8. On the opposite end of the system, behind the tail pipe, try to get the holes to line up. Don’t worry if they don’t meet exactly. If they come up short, take two garden shovels, placed the handles in the new exhaust system intake pipes and pry outward to make up some of the difference. They may still not align exactly, but should be close enough that you can place a big screwdriver through the exhaust flange, gasket and heat exchanger flange bolt hole and use it to gently leverage everything into place long enough to get the first bolt on that side. Then add the rest of the bolts through the flanges on both sides, hand tightening each.
  9. Tighten everything up. Now tighten the bolts the rest of the way down. The new exhaust should be secure to the heat exchangers. Now, tighten up any bolts for the hangers. Some of these are designed to allow some movement in the system, so don’t over-tighten any of those.
  10. Check your work. Visually inspect the installation and wiggle the new exhaust to make sure it is not loose from the heat exchangers anywhere. With the van in neutral, the parking brake on and the wheels blocked, crank the engine and let run for a few minutes. Before the engine gets too hot, feel around where the flanges meet. If you have any leaks, you should be able to feel the exhaust blowing through them. Bolts may need to be tightened up at the flanges to compress the gaskets right. If that does not work, take the new system off and make sure again that the gaskets and mating surfaces are aligned right and smooth, with no defects. Again, sometimes you might have to use two gaskets to get a good seal with aftermarket exhaust systems.
  11. Reinspect everything a day later and then a week later. Exhaust systems heat and cool, plus they vibrate. This can loosen bolts and fasteners. It is a good idea to check that everything stays tight. After a week, it is a good idea to go over most areas like this every month or so to make sure nothing has come loose. It also does not hurt to keep an ear on your motor. Given the distinctive sound of the VW air-cooled engine, it’s usually easy to ear if you have even a relatively minor exhaust leak.

Tips

  • Performance exhausts. Some of these work, some don’t. For example, an EMPI-type four-tip Monza exhaust is a simple install and will solve undercarriage exhaust leaks, but it also can release exhaust out in the center of the rear of the bus, creating the “station wagon” effect with the fumes. Also, having four, spiked tail pipes sticking out at shin height below the rear hatch can result in bruises and burns. A chrome, quad monza exhaust looks out of place on a VW camper.
  • Other bolt-on performance exhausts for these model vans may work better, but there is usually a trade-off somewhere, often in ground clearance.
  • As replacement options go, there are only a few.
  • Replace the heat exchangers. Can be expensive, but changing the exchangers to a different model year can be done with minor modifications. If your heat exchangers are shot and also have to be replaced, that would be the way to go.
  • Find used parts. Used parts for vans are great – especially when it comes to keeping camper interiors as original as possible. However, any used exhaust part should be considered suspect. Even if you get one that works and does not leak, how much life is there really left in it?
  • Buy a complete replacement exhaust system. This is a single welded unit that has a horizontal muffler and tailpipe and replaces everything aft of the heat exchangers. It has all the hanger parts in the right places, fits nicely under the van with plenty of clearance and looks relatively original. It also spits the exhaust off to the side so it does not end up getting sucked back into the Bus. This is the best bet.

Warnings

  • NOTE: Some states, like Alabama have very lax emission rules. If you live in California or other places with more stringent requirements, make sure you install a system that meets your state’s regulations. Also check the law to see if your vehicle is covered under a grandfather clause that would exempt it from strict emissions rules.
  • WARNING: Exhaust systems are hot – especially in air-cooled VWs – and can hit several hundred degrees quickly while the engine is running. Be careful not to burn yourself while working on an exhaust system and allow adequate time for everything to cool off before attempting repairs or adjustments.
  • WARNING: Damaged exhausts can leak carbon monoxide under the frame or directly behind the Bus. This can also happen with some performance exhausts and is dangerous because of the “station wagon” effect, where the flat back of the vehicle creates a vacuum as it goes down the road and can suck the exhaust back into the passenger compartment.

Things You'll Need

  • Replacement exhaust system, whether a complete kit or a performance set up. Make sure it has the triangular flanges that are oriented for a stock system and are designed for a bus. There are some other mounting systems for performance systems and other air-cooled VW models that use different triangular flanges
  • Gaskets. Make sure your new parts come with the necessary gaskets that fit your model. There are metal and asbestos-like fiber ones out there – you might have better luck with the fiber ones though. Also, if they are not provided, just order an extra set. They are handy to have on hand and in some cases, you can use two of the fiber gaskets to get a good seal
  • Mounting hardware – six bolts, washers and nuts (three sets for each flange), plus any additional bolts necessary for the hangars if they are missing.
  • Tools – a good flat box wrench, or two, and a socket wrench and set. Generally the bolt sizes are 13 mm heads and the hangar bolts had 12 mm heads. Also, one long, heavy-duty Phillips screwdriver
  • Lubricant – some kind of penetrating oil like WD40 or Breakfree
  • Big sheet of cardboard

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References

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