Zippy gets a new exhaust system

Zippy's old muffler and heat exchangers had been in bad shape for years. But since we really only drive on sunny days with the top down it was never a priority to deal with. If we had to put the top up, we might have suffocated. The exhaust was leaking into the heat exchangers, and that was just one of the problems.

Once I got the 911's sunroof subdued (allowing me to park it out in the rain safely), Zippy got into the garage & up on the Quickjack for some serious TLC.

Hot take? There is nothing as rusty as an old Bug's exhaust system. It is truly amazing how bad they can get.

I will die on this hill.

I bought a muffler, a pair of new tail pipes, both heat exchangers and all of the clamps, gaskets and hardware I might need to survive this journey. Most of the parts are very inexpensive. The heat exchangers and muffler will run several hundred dollars though.

If you haven't had the pleasure, the heat exchangers are really the exhaust manifolds which then have a housing over them where air is blown over them to heat it up which provides heat/defrost to the passenger compartment1. The exhaust manifold has a pipe in the front of the engine and another in the rear. Then the muffler connects to the two heat exchangers, and finally you install the iconic chromed tailpipes into the muffler. Easey peasey? Not really.

Parts:

Muffler (year & market specific). The 1974 US market one I bought has a bung for an EGR valve (which this car never had) so I had to buy a special bolt to block that off. Luckily your corner auto parts store will probably have these in the right size. This one needed an M16-1.5 plug which is also a common oil drain plug size.

Tail pipes x 2

Muffler hardware (clamps, gaskets, nuts & bolts) - often sold as kits.

New exhaust stud kit (optional but a good idea to have on hand)

Heat Exchangers (L & R)

Opt - new cabin heater hoses, heater hose gaskets (rubber surrounds), heater cable pivots, various tin pieces, tin screws

Tools:

S-shaped wrench to get to remote nuts on heat exchanger

Open end & box wrenches for exhaust nuts

1/4 & 3/8 socket sets with wobble extentions, adjustable heads.

(basically pull out all your trick tools)

Torch or bolt blaster (or don't even try this)

Needle noise pliers, screw drivers, etc. for all the odd small parts & clips.

Basic order of operations

1. Remove the air hoses in the engine bay

2. Remove the engine tin (lots of little screws, and several different pieces large and small.)

3. Remove the clamps & bolts holding the muffler on to the heat exchangers, if you can.

   1. If you can't, you may need to saw it off. You should be prepared to do exactly that.

   2. My muffler clamps were broken or gone and the muffler had rusted to the heat exchangers.

4. With the muffler out of the way, try to remove the 4 nuts on each heat exchanger without breaking the studs.

   1. There are 2 on the front side and 2 at the rear. They will be very rusty and you should use heat & penetrating oil (or wax) to gently work them loose so they don't just shear.

5. Remove the heat exchangers, disconnecting them from the heater cables and cabin air pipes

Installation is just the reverse, but may not be easier.

The trick with penetrating oil - or wax - is when you heat the fastener up, it will wick the fluid into the threads which will lubricate them. An old candle can work quite well if you don't have penetrating oil handy. The heating/cooling cycles also weaken the rusted fastener as it grows and shrinks.

If you are missing any of the engine tin, this is a good opportunity to replace it. The various pieces are available from several sources and mostly fit well. You may need to tweak them here or there, but it's 100% worth it to get this right. Aircooled engines depend heavily on proper airflow to stay at a safe operating temperature. The 1600cc Beetle engine carries only 2.5 quarts of motor oil which also has to both lubricate & cool the engine using a rather tiny oil cooler under the fan shroud. The tin at the rear is helping to protect the engine bay from the heat of the exhaust. The tin on the bottom of the engine is ensuring proper airflow over the cylinders and out the rear of the car.

Lets dig in:

I chose violence. The bolt blaster really works, can’t recommend it enough! And when it’s still not enough, there is always the hacksaw.

I started out by removing the air hoses and then removing the tin:

The 2 outer air ducts are from the head exchangers. The inner one on the RH side is added on to send warm air into the air cleaner in cold weather.

More rust than fasteners here. The pre-heater pipe (foreground) bolts to the muffler through the tin. I had already cut the lower part of the muffler off here; soon I would cut off these little air boxes to get better access to the exhaust manifold nuts. It was a rusty mess. 20/20 hindsight I should have ordered new pre-heater pipes. They’re inexpensive.

After Penetrating oil and the Bolt Blaster. Magic. I was able to get 7 of the 8 off without damage.

Penetrating oil and heat got this apart nicely, believe it or not!

This one stud sheared off. At least it is at the rear of the engine so there’s room to drill it out.

the right side studs came out nicely once the threads were chased. I’ll replace all the studs when I pull the engine to rebuild it.

Zippy was missing some key tin bits (the sheet metal that guides air around the engine to keep it cool) and here the heat exchangers are both off of the car. Cleaning this all up and installing the tin was an important step. It was pretty nasty down there and hard to even tell where the oil was coming from. It has several leaks.

Test fitting a new heat exchanger here. The replacement exhaust stud kit came with brass nuts to help avoid rust in the future.

I used plenty of copper high temp never-sieze to help protect against corrosion.

Once the heat exchangers are in, the lower tin screws into them and you can clamp on the muffler and heat pipes. Leave everything a bit loose as you go, it will need jiggling and convincing to fit.

Fancy new tailpipes, finally!