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" One day your engine starts to rumble a little more than usual. Or was that just a passing airliner? Over the next few weeks the sound becomes a steady drone -- and then you notice a faint smell of exhaust lingering inside your car. Even minor leaks in the exhaust system need to be addressed right away -- before the kids start nodding off, mid-video game, in the back seat. Although safety is the biggest issue, it&amp;#039;s not the only one. Fuel economy also can suffer: Your Check Engine light may come on because the oxygen sensor downstream of the exhaust leak is picking up extra O2, forcing the engine computer to order more fuel from the injectors. Fortunately, replacing a failed crossover doesn&amp;#039;t have to be a job for the shop. It&amp;#039;s basic plumbing, and if you&amp;#039;re not intimidated by the need to remove rusted fasteners, this may be a job to attempt yourself. The exact procedure isn&amp;#039;t worth recounting here -- basically, it&amp;#039;s a straight remove-and-replace job. But we can give you some pointers. Not Your Father&amp;#039;s Crossover Just to be clear, we&amp;#039;re not talking about a performance crossover pipe -- what is commonly called an H-pipe (or Y-pipe on a rear-wheel-drive vehicle). We&amp;#039;re talking about the exhaust crossover pipe that routes hot exhaust gases from the front cylinder bank of a transverse V6 or V8 to the rear cylinder bank. It travels from the front manifold above the transaxle to the rear mani\u00ADfold, where it connects to the rest of the exhaust system. Paying the Price The engine and manifolds expand and contract as they warm up and cool off, and the crossover needs some type of flexible joint to keep from cracking, either a flexible metal bellows (as here) or ball joint, spring-loaded flanges at either end. The latter tend not to seal as well, which is probably why our &amp;#039;98 Ply\u00ADmouth 3.3-liter V6 (and the gazillion others that Chrysler built) used a more costly bellows. We mention this only because our replacement pipe was not available in the aftermarket. It was a dealer-only piece and cost upward of $500. Yikes! So be prepared to shell out if you&amp;#039;re forced to do a similar job. Change Is Good And don&amp;#039;t think you can get away cheap by trying to patch, weld or braze your busted crossover pipe -- or, for that matter, any other part of the exhaust system. The intense heat and the repeated heating/cooling cycling mean that a welded repair of almost any part of an exhaust system is probably going to fail. A quick fix may work initially but there&amp;#039;s no telling how long it will last before you&amp;#039;re eating fumes again. Don&amp;#039;t ask how we know this. Plus, buying the correct replacement part means you&amp;#039;re likely getting an upgrade. We noticed two obvious differences between the old and new parts (one improvement solved a flaw for which Chrysler had originally issued a Technical Service Bulletin in 1998): 1. A problematic bracket that supported the middle of the origi-nal crossover pipe has been eliminated. (Ours had already failed at a welded joint.) 2. The flexible metal bellows have been improved by switching from a multipart crimped design to more robust, one-piece swaged bellows. Our exhaust leak originated at several failing crimps in the middle of the old pipe. You can see the trail of black exhaust gases in the photo on page 141. That seemingly small leak made our minivan sound more like a garbage truck. Handling the Hardware Because of its location high up in the hot engine bay, away from moisture and road salt, the exhaust crossover pipe leads a pretty good life. For that reason, the old one shouldn&amp;#039;t be much of a chore to remove. Or so we thought. What was supposed to be a morning project turned into an all-day affair when only three of the four flange bolts threaded out readily. There&amp;#039;s always that one rusted bolt way in the back, up against the firewall, where you can&amp;#039;t reach it easily. We worked on the bolt from hell for more than an hour with every manner of socket, extension and flex handle -- all to no avail. We finally wound up grinding off its head with a cutoff wheel, and attacking it from above and below. Here are some of the aforementioned tips for exhaust work. First, before even getting started on the project, douse every fastener you&amp;#039;ll be working on with penetrating oil while the engine is hot. Then do something else for a spell while that soaks in. Next, remember that stubborn hexhead fasteners require six-point sockets. Don&amp;#039;t use 12-points -- they tend to round off bolt heads. Plan to replace any exhaust hardware that you remove. After a few years in service, nuts and bolt heads are invariably undersize -- corrosion literally etches a few thousandths from the outside of these fasteners. Also, the threads corrode and become difficult to turn. A couple of bucks invested in new bolts, nuts and washers will make short work of reassembly. Use correct hardware from the auto parts store, not the stuff left over from that swing set you assembled last summer. Here&amp;#039;s one trick we learned years ago from an old Volkswagen mechanic: If a nut won&amp;#039;t unthread when you attempt to remove it, try to tighten it. Most smaller fasteners will simply fail. Larger bolts (like the 10mm hardware on our manifold) will take a lot of muscle to twist off. In the toughest cases, we&amp;#039;ve resorted to using a cold chisel to split a nut open across one of the flats, which lets it spin readily. Another tip applies to any assembly that requires multiple bolt holes to line up simultaneously, like the flanges on the ends of the crossover pipe. Always run in the threads halfway on all the bolts before finger\u00ADtightening them. This lets each bolt line up and start easily. We like to use antiseize compound when reassembling new or used exhaust hardware. Guess who is probably going to be the next person to disassemble that part.  1] Hidden under all that stuff is the old, leaking crossover pipe. We removed the air cleaner and battery to improve access.     2] First, soak all the hardware in penetrating oil, preferably for a few hours.     3] This bolt on the rear manifold proved tough to turn. Eventually, we cut it off.     4] Once we got the old part off, it took only a few minutes to snake the new one into place and start all the fasteners a few turns. Odds are, you&amp;#039;ll need new bolts and nuts.     5] Fingertighten the bolts first, then tighten properly with a socket. We used antiseize compound, in case we ever need to remove them.     "^^<http://www.w3.org/2001/XMLSchema#string>
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