Camshaft failure is a major repair for any type of engine design, whether it be overhead valve (OHV) or overhead cam (OHC). It doesn’t matter if the engine is a rear wheel drive (RWD) vehicle or one that is front wheel drive (FWD), this job is going to take some time. In addition, the camshaft follower(s), depending on the extent of the damage, may have to be replaced.
Let’s review the replacement of the camshaft and rocker arms (commonly referred to as cam followers) in the 3.6L V6 VVT engine, also known as the Pentastar® engine. This engine is used across the board in FCA US LLC’s vehicle lineup, so you’ll find it in Minivans, Chrysler 200, 300C, Dodge Challenger, Charger and even in the Jeep® Grand Cherokee and Wrangler vehicles.
This engine is a dual overhead cam (DOHC) design, utilizing unique right and left castings with four valves per cylinder. The valvetrain uses cam followers with hydraulic valve lifters. The camshaft bearing caps are made of powdered metal. The location and direction of each cap is marked on the side of the cap.
Each camshaft is made from nodular cast iron and each has a pressed on magnetic timing wheel that is magnetically coded. Two camshaft position (CMP) sensors are located between the timing wheels. Attached to the rear of the right exhaust camshaft is a centrifuge which is part of the crankcase ventilation system. Camshaft endplay is controlled by two thrust walls that border the nose piece journal.
CAMSHAFT ANDCAM FOLLOWERS REMOVAL
The camshafts can be removed without removing the cylinder heads. Remove both cylinder head covers, ignition coils and spark plugs. Remove the left and right oil control valves. While the oil control valve removal procedure is detailed in the appropriate service manual. Here’s a few important details to keep in mind.
- The engine must be rotated to the Top Dead Center (TDC) of the compression stroke in cylinder #4
- The left side cam phaser scribe lines should face away from each other; the arrows should point toward each other and be parallel to the head cover mounting surface
- There should be 12 chain pins between the exhaust cam phaser triangle marking and the intake cam phaser circle marking
- Be sure to properly mark both sides of the cam chain at the phaser timing marks with a paint pen, or equivalent
Following these marking procedures will ensure proper re-installation of the oil control valves.
Caution: The magnetic timing wheels must not come in contact with any magnets or strong magnetic fields
Rotate the left camshafts counterclockwise to position the alignment holes approximately 30º before TDC. This places the camshafts in the neutral position (no valve load). For both sets of camshafts, loosen the camshaft bearing caps in the sequence shown in the service manual. Mark the rocker arms before the camshaft is removed. Remove the bearing cap bolts, the bearing caps and the camshafts. Remove the rocker arms.
CAMSHAFT AND CAM FOLLOWERS INSTALLATION
Lubricate the cam followers with clean engine oil before installation. Position each cam follower onto the valve lifter and valve stem. Be sure the valve stem fits securely into the cam follower guides. Lubricate the camshaft journals with clean engine oil.
Caution: Do not rotate the camshaft more than a few degrees independently of the crankshaft; valve-to-piston contact can occur, resulting in possible valve damage
Install the camshafts in the correct position. The right side camshafts are installed at TDC by positioning the alignment holes vertically (Figure 1). The left side camshafts are installed with the alignment holes positioned approximately 30º before TDC. When positioned correctly, the camshafts are at the neutral position (no valve load), easing the installation of the camshaft bearing caps (Figure 1).
The camshaft bearing caps are identified numerically (1 through 4), intake or exhaust (I or E) and should be installed from the front to the rear of the engine. All caps should be installed with the notch forward so that the stamped arrows (<) on the caps point toward the front of the engine. Install the camshaft bearing caps. Tighten the bolts finger tight. Verify that the cam follower (3) is positioned over the valve lifter (4) (Figure 2). In addition, verify that the cam follower roller (2) is seated to the cam lobe (1).
Using a mirror (Figure 3), verify that the valve stem (4) is centered between the cam follower guides (3). In addition, verify that the camshaft lobe (1) is centered over the cam follower roller.
Note: If any of the rocker arms are not installed properly, loosen the camshaft bearing caps and reposition the rocker arms
Following the sequence pattern shown in the appropriate service manual, tighten the camshaft bearing cap bolts to 89 in-lbs.
Install the left and right oil control valves (variable valve timing assembly). To complete the installation, check the end play of each camshaft.
Mount a dial indicator set (C-3339A, or equivalent) to a stationary point at the front of the engine. Place the probe perpendicular against the oil control valve. Move the camshaft all the way to the end of its travel. Zero the dial indicator. Move the camshaft forward to the limit of travel. Read the dial indicator. Compare the measured end play to the specification. The end play should be in the range of 0.003″ – 0.010″.
A STAR Case bulletin, S1309000016, was released just over two years ago (March 18, 2014) in regards to the rocker arms used in the Pentastar® engine. The symptom/vehicle issue is ticking/tapping noise from the upper engine area. In addition, this failure can also set a Diagnostic Trouble Code (DTC) for an engine misfire.
Remove the components to gain access to the engine valve train. Inspect each rocker arm roller bearing for missing or worn needle bearings. Also, inspect for a collapsed valve lifter. Replace, as required. This condition is typically found on vehicles with mileage accumulation of 15,000 miles or more.