Engine noise is a common complaint on 1991 and newer Dodge Caravans and Chrysler minivans with 3.3L and 3.8L V6 engines. A variety of things can cause engine noise on these vehicles, some of which are a relatively minor concern while others may indicate a need for major repairs. Common engine noise complaints on these minivans include tapping, ticking, clattering, rattling, knocking, rapping, buzzing, whistling, squealing and groaning sounds from the engine compartment. In some cases, the noise is only noticeable immediately after starting the engine. Other times, the noise comes and goes, changing with engine speed or vehicle speed. With some minivans, the noise has always been there (for years!) but has never gone away. Of most concern is ANY noise that suddenly occurs. If your engine has been relatively quiet but is not making a strange noise, it should be investigated without delay. Normal Engine Noise or Abnormal Engine Noise? Chrysler dealers often tell minivan owners that some of these sounds are "normal" and are nothing to be concerned about. Even so, ANY unusual noise coming from the engine compartment should never be ignored. If a Chrysler dealer won't address the problem, take your minivan to an independent repair shop for a second opinion. To date, Chrysler has never admitted to having an engine noise problem with their minivans, nor have they published any technical service bulletins on diagnosing or repairing engine noise on these vehicles. It's as if the problem doesn't exist! But according to many Dodge, Plymouth and Chrysler minivan owners who have the 3.3L and 3.8L V6 engines, noise IS a problem. 3.3L & 3.8L V6 Engine Noise Issues The 3.3L and 3.8L V6 engines in Dodge, Plymouth and Chrysler minivans are older style pushrod engines (not overhead cam engines as is the case with the 3.0L and 3.5L V6 engines). Both engines have cast iron blocks and aluminum cylinder heads. The 3.3L engine has been in production since 1990, and the 3.8L engine since 1991. Over the years, these engines have been revised and improved somewhat with changes to the cylinder heads, valvetrain and cam drive. In 2000, they changed the cylinder heads to incorporate an EGR (Exhaust Gas Recirculation) valve for lower emissions. In 2001, they revised the cylinder heads again, changing the design of the rocker arms and rocker shaft to improve reliability and reduce noise. The earlier style stamped steel rockers were replaced with welded rockers, and the 4-bolt rocker shaft was replaced with a much stronger 7-bolt rocker shaft. The older 4-bolt shaft was less rigid and prone to cracking the shaft support stands in the cylinder head. In mid-2002, the former aluminum intake manifold was dropped and replaced with a lighter (cheaper?) plastic intake manifold, and in 2004, the stamped steel valve covers were replaced with plastic covers (to dampen valvetrain noise?). In 2004, the camshaft gear was changed to accommodate and new engine computer and camshaft position sensor. The following year, Chrysler changed the cam drive again to a narrower (quieter?) gear and chain. In mid-2007, Chrysler went to slightly smaller (quieter?) roller valve lifters. Engine Valvetrain Noise One of the most common engine noise complaints on the older 3.3L and 3.8L V6 engines is ticking, tapping or clicking noises from the area of the valve covers. This is typically valvetrain noise caused by excessive lash (clearance) between the pushrods, rocker arms and valves. Hydraulic valve lifters use oil pressure to take up slack in the valvetrain. When a cold engine is first started, oil pressure fills up the plunger cavities inside the lifters. This pushes the pushrods up tight against the rocker arms to remove any clearance (lash) between the rockers and the tops of the valve stems. This allows the valvetrain to operate quietly with zero lash. It also allows the lifters to compensate for changes in valve lash that occur as a result of valve and cam wear. But if oil pressure is slow to reach the lifters, or the little holes that allow oil to enter the lifters are plugged or restricted, the lifters may be slow to pump up or not pump up at all. The leaves too much clearance between the rocker arms and valve stems, resulting in ticking, tapping or clicking noises from inside the valve covers. Several underlying conditions can cause this type of noise. One is using the wrong oil filter or a cheap oil filter that does not have the correct anti-drainback valve. The anti-drainback valve inside the oil filter prevents oil from draining out of the oil galleys when the engine is shut off. This allows oil pressure to increase more rapidly the next time the engine is started. If the anti-drainback valve allows the oil to dribble back into the engine, it will take longer for oil pressure to increase the next time the engine is started — which can result in valvetrain noise until oil pressure builds up. Valvetrain noise that continues after the engine has been running more than a minute or so usually means something is wrong. The engine may have a problem with low oil pressure. This could be due to a worn oil pump, or worn main or rod bearings on the crankshaft. It could also be the result of one or more bad lifters (oil holes plugged up or the plunger inside is sticking), excessive wear in the valvetrain (worn cam lobes, lifters, rocker arms or the tips of the valve stems due to high chilometroage, infrequent oil changes or oil contamination), or possibly a bent pushrod. First, check the oil level in the crankcase to see if it is low as this can cause valvetrain noise (usually if the level on the dipstick is more than two quarts low). Do not assume the oil pressure warning light will come on if the oil level is low. It won't! The light only comes on if oil pressure is dangerously low, and by then it may be too late to prevent serious engine damage! If the oil level is okay, a low oil level is not the cause. The next check would be to check oil pressure at the oil pressure sending unit with a gauge. If oil pressure is low, the oil pump is probably worn and needs to be replaced. Quieting Noisy Valve Lifters Lifter noise can sometimes be fixed by adding a bottle of engine flush to the crankcase, or having the oil system professionally flushed at a repair shop. The solvents and detergents in the cleaner will hopefully loosen the varnish and carbon deposits that are causing the lifters to stick or that are blocking the oil fill holes in the lifters. If you are using a crankcase additive, follow the directions on the product. This usually involves driving your vehicle for a period of time (to give the product time to work), then changing the oil and filter. If the noise continues after flushing and changing the oil, it probably means you're looking at having one or more bad lifters replaced. This can be done without pulling the engine, but the valve covers and intake manifold do have to come off the engine. Before you spend money on repairs, you might try switching to a synthetic 5W-20 motor oil. With many high chilometroage engines, switching to a heavier viscosity oil (10W-30 or even 20W-50) often helps to reduce engine noise due to normal wear. But on these engines, the problem isn't so much wear as it is getting oil quickly to the lifters and upper valvetrain. Switching to a synthetic 5W-20 oil, which is thinner and flows more easily than 5W-30 or 10W-30 oil, seems to quiet these engines down. Broken Rocker Shaft Support Valvetrain noise on 2000 and older engines can be caused by a cracked or broken rocker shaft support stand on the cylinder head. These were the ones with the weaker 4-bolt rocker shafts and stamped steel rockers. Normally, the cylinder head has to be replaced (though some head rebuilder shops can TIG weld the cracked or broken support stand to repair the original head). A less expensive repair option that sometimes works is to drill out the bolt boss in the broken stand, install a Heli-coil insert and use a longer bolt to support the rocker shaft. Engine Cam Bearing Failure The cam bearings in the 3.3L and 3.8L V6 engines can fail if the engine has a low oil pressure problem or has contaminated (dirty) oil (usually as a result of not changing the oil and filter often enough). When the cam bearings are deprived of normal lubrication, metal can be scraped off the bearings by the camshaft. The metal particles then get into the oil stream and are carried throughout the engine. This can plug up the oil holes in the lifters or cause them to stick, and it can be very damaging to the oil pump (which pulls in unfiltered oil from the crankcase). If the cam bearings are worn, the camshaft can deflect and wobble in its bore, increasing valve lash and noise. Typically, you will hear tapping or rattling noises from the middle area of the engine. There's no easy fix for this as it requires overhauling the engine (tearing everything apart, removing the old cam bearings, checking the alignment of the cam bores, possibly line boring the cam bores, installing new bearings and putting everything back together. Engine Connecting Rod Knock A deep metallic rapping or knocking noise from the bottom area of the engine is bad news. It means the oil pump is not developing normal pressure due to wear (or an extremely low oil level) and/or one or more connecting rod bearings may be worn or damaged. If a rod bearing is failing, it will only be a matter of time until one of the bearings seizes and/or causes a rod to break. When that happens, it's the end of the road for your engine. The fix requires rebuilding or replacing the engine. A rod bearing failure usually damages the crankshaft, so the minimum repair would be to remove the engine, tear it down and have the crankshaft reground, or replace it with a reground crankshaft kit (which includes new undersized rod and main bearings). If a connecting rod broke, it would also have to be replaced along with any other damaged parts. If the engine has a …

Fonte: AA1Car.com