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Removing a Diablo Muffler

There are a number of times when one may wish to remove the muffler from a Lamborghini. Almost any major engine repair for example will require the muffler to be removed. Fortunately this is relatively easy to do in most of the cars. I will illustrate it here with a Diablo. I will also outline how to go about repairing the muffler box if one of the catalyst attachment bolts gets broken. This is common on older (often rusted) cars. 

First a few obvious points. Make sure the car engine is cold. It often helps to put reagents that loosen rusted nuts on them as few hours beforehand. The nuts used to attach the catalyst to the muffler box reach high temperatures. They are often difficult to open in older cars and can snap off (see below).   The muffler box itself is quite heavy. Since you have to bend over the car to get it out. Watch your back and/or get a friend to help lift it out.

The whole process is really quite simple. I will illustrate most of the steps with pictures.  First remove the rear section (and wing) of the car. This exposes the silver heat shield that covers the hot muffler box (fig 2).  Next get under the car and open the two bolts on the two C-clamps that attach the catalysts to the engine (fig 3).  Remove the 3 nuts on the bolts that attach each catalyst to the muffler box (fig 4). Take care with these nuts they can break easily.  Figure 5 shows the two catalyst units removed. Note you can actually get the muffler box out without removing these two catalysts. However the whole unit is quite heavy and difficult to get out.   Next remove the two nuts on the side of the muffler box that attaches it to the frame of the car (fig 6). Next remove the rear mounts of the muffler box.  There is no need to open the large bolt containing the spring.  Just open the 4 attachment screws as shown in figure 7. Finally remove the two c-clamps under the muffler box that hold the tail pipe in place (fig 8).  Then lift the muffler box out of the car taking care not to scratch anything.  Figures 9 - 11 show the removed muffler box, catalysts and tail pipe.

While you have the tailpipe out, you may wish to spray it with (black) high temperature paint as shown in figure 11. You might also wish to brush the rust off the various c-clamps and spray them as well. This prevents them form rusting in the future.

What if you shear off a nut.
Even with the best care one can shear off a muffler box bolt when they are old or rusted.  This happened to one of mine as shown in figure 12.  Fortunately this is easy to repair. First cut the broken bolt down to the surface of the box (fig 13). Then drill out the old nut as shown in fig 14. Use a drill bit one size smaller than the bolt.  Then with a treading die (available in most hardware stores)  re-do the treads as shown in figure 15.  Remember Lamborghini cars use metric measurements. You need a 8 mm tread in this case.   Figure 16 shows the new treaded box. Screw in a new bolt with a nut attached as sown in fig 17. Then cut the extra treads above the nut as shown in figure 18.  Then screw off the nut.  (You attach the nut first so you reform the start of the tread as you screw the nut off).
Reattaching the muffler
Reattaching the muffler is simply a reversal of all of the above. Place the muffler box back into the car. Start first by attaching the two catalyst units through the c-clamps to the engine. Then attach the catalyst units (3 nuts each) to the muffler box. Them tighten down the two side nuts that hold it to the frame of the car.   There is one trick in attaching the rear muffler box spring mounts.  Use a "Vice grips" to press the attachment bracket to the frame of the car so you can then screw in the 4 small nuts (fig 7).  It is important to start with the c-clamps at the engine, then catalyst then box mounts. If you d it in any other order things may not line up properly. It is difficult for one person to attach the tailpipe by holding it in place and at the same time attaching the c-clamps. A trick I found helpful is to string the tailpipe up with a cord as shown in figure 21 and then maneuver it into position with the c-clamps.

Start the engine up in a well, ventilated area and check all joints are tight.  If there is a leak, you will hear it or feel the exhaust blowing against the back surface of your hand. Try tightening nuts further and/or open a joint and put one of the many muffler sealing pasts on a joint.  If you are careful you should not have broken the gasket that seals the catalyst units to the muffler box. If you did pick two up at any muffler bringing yours with you.  Replace the heat shield and rear section of the car and you are done.


Fig 2. Muffler box exposed Fig. 3. Remove engine c-clamps Fig 4. Remove catalyst bolts
Fig 5  Catalyst removed from car Fig 6   Remove side bolts Fig 7  Remove screws holding rear spring
Fig 8.  Remove c-clamps holding tailpipe


Fig 9. Muffler box Fig 10. First set of catalysts
Fig 11 Tailpipe


Fig 12 Broken muffler stud Fig 13 Cut stud level with surface
Fig 14 Stud cut to surface


Fig 15 Drill out old stud Fig 16 Tap in new 10 mm treads
Fig 17 New treads complete


Fig 18 Insert 10 mm bolt with nut Fig 19 Cut bolt above nut
Fig 20 Finished new stud with nut


Fig 21 Strapping up tailpipe during attachment


This page was last modified on 03/12/2014

This page was last modified on 09/06/2014