 Overhead camshaft (OHC) engines have become the dominant engine design over the last decade. With this design, a longer drive mechanism, usually a belt, is required, due to the increased distance between the crankshaft and camshaft(s). Compare this to an overhead valve (OHV) layout. Timing belt failures were quite common with the early belt designs. Recommended change intervals were usually 60,000 miles, but advances in materials have significantly increased the service life of timing belts. In fact, timing belt failure does not occur nearly as often as it did in the past. Recommended change intervals for timing belts on today's vehicles are as long as 105,000 miles (check the appropriate service manual).
Timing belts are used in several Chrysler Group engines. Among these are the 2.0L 4-cylinder SOHC used in the Neon, the 2.4L 4-cylinder DOHC used in the PT Cruiser and Sebring/Stratus models, and the 3.5L V6 used in the LH models.
Even with the engineering advances that have improved the quality of timing belts, timing belts still fail. And replacement can be tricky with transverse engines mounted in small engine compartments, such as those found in the Dodge Neon or PT Cruiser. The simple fact of the matter is that there just isn’t a lot of working room under the hood.
The timing belt replacement job in the LH models is a bit easier than in other vehicles for a couple of reasons. First of all, the engine compartment is larger and there is more working room than in the smaller cars. Second, the V6 is not transverse mounted, allowing you to work from the front of the vehicle. With this in mind, let's take a look at timing belt replacement with the hope of making this potentially tough job a bit easier. Our focus, though, will be on the transversemounted, 4-cylinder engines.
Timing Belts, Water Pumps and Other Considerations In addition to driving the camshaft(s), the timing belt also drives the water pump. On OHV engines, the water pump is an external component with a separate drive mechanism. Not so with an OHC design. The modern water pump now resides inside and is driven by the timing belt. This is significant because whenever a water pump or timing belt is replaced, the other component should also be replaced. Due to the time and effort required to access the timing belt and water pump, replacing both at the same time only makes sense.
Figure 1 shows a typical timing belt arrangement for an OHC engine. The water pump is component number 4. Note the teeth on the pump pulley, where the timing belt is fit in order to drive the pump.
In some cases, you might not want to replace the timing belt when the water pump fails. For instance, if the pump fails after a relatively short service period, the belt is probably OK. Also, if you know that the belt has recently been replaced, there’s no need to replace it. If you’re not sure, inspect the belt. Look for cracks, missing teeth, signs of peeling and abnormal wear (see Figure 2). Any of these conditions indicates that the belt should be replaced.
 As a last consideration, timing belt replacement should be performed at the recommended interval to prevent possible engine damage. Several DaimlerChrysler engines do not have free-wheeling provisions. In other words, if the timing belt fails, an ascending piston(s) can strike a valve(s) in the open position, causing extensive and expensive engine damage. The 1.6L SOHC, 2. 0L SOHC, 2.0L DOHC and the 3.5 V6 all fit into this category. The 2.4L DOHC, used in the minivans, PT Cruiser and Sebring/Stratus, however, is a free-wheeling engine. A broken timing belt will just leave you on the side of the road with no additional engine damage. The 2.4L is a free-wheeling engine when it comes to piston to- valve clearance. However, the valves may hit each other should the timing belt break.
Timing Belt Replacement
The timing belt replacement procedures outlined here have been generalized, but are taken from those specific to the 2.4L 4-cylinder DOHC engine installed in the PT Cruiser. For any deviations, check the specific service manual for the particular vehicle you are servicing. The first step in any timing belt replacement job is to disconnect the negative battery cable.
Next remove the timing belt covers. In many cases, that's much easier said than done. In our example, the upper front cover is removed after the upper torque strut is set off to the side. If the PT Cruiser is turbocharged, the A/C system lines must be disconnected at the junction block near the upper cover.
To remove the lower front cover, the following components must be removed or disconnected in the following order: (1) right front tire/wheel assembly, (2) right splash shield, (3) accessory drive belts, (4) crankshaft damper, (5) lower torque strut, (6) exhaust system at the exhaust manifold, (7) A/C pressure switch, (8) A/C lines at the coupling block, (9) upper torque strut, (10) torque strut bracket, (11) upper radiator closure panel, (12) power steering pump and bracket, (13) right engine mount through bolt, and (14) engine support bracket.
It’s easy to see all the additional work that must be done when replacing a timing belt on a transverse-mounted engine. Now you can understand why it is recommended that the water pump be replaced at the same time.
After the timing covers have been removed, you now have access to the timing belt. Before the belt is removed, however, the camshaft timing marks must be aligned (this must be done on all engines). Rotate the crankshaft sprocket until the TDC mark on the oil pump housing aligns with the TDC mark on the crankshaft sprocket (see Figure 3). Next, loosen the timing belt tensioner lock bolt and insert a 6 mm Allen wrench into the hexagonal opening on the top plate of the belt tensioner pulley. Rotate the top plate clockwise until there is enough slack in the timing belt for removal. Remove the timing belt.
Before installing the new belt, set the camshaft timing marks so that the exhaust cam sprocket (on the left as viewed looking toward the front of the engine) is 1/2 notch below the intake cam sprocket. Install the timing belt counterclockwise, starting at the crankshaft sprocket and going around the water pump sprocket, idler pulley, cam sprockets and tensioner. After the belt is installed, rotate the exhaust cam sprocket counterclockwise to align the timing marks and to take up any slack in the belt.
Tighten the tensioner by rotating the top plate counterclockwise. The tensioner pulley will move against the belt, and the tensioner setting notch will start to move clockwise. While watching the movement of the setting notch, continue rotating the top plate counterclockwise until the setting notch is aligned with the spring tang (see Figure 4). Tighten the tensioner lock bolt.
Manually rotate the crankshaft clockwise two complete revolutions to seat the timing belt. Reposition the TDC marks as described earlier. Check the alignment of the setting notch and spring tang. These marks should still be aligned. If not, repeat the procedure outlined in the previous paragraph. Reinstall the timing covers and all those components that were removed to gain access to the timing belt, and you’re all done.
Note: You should always refer to the appropriate Service Manual before attempting any repair. Pay particular attention to any notes, cautions and warnings.
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