Pelican Technical Article: BMW E30 Timing Belt Replacement

This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.

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     Replacing the rubber timing belt is one of the most important maintenance tasks for the six-cylinder E30 engine. As the engine ages and mileage climbs, an old, worn-out timing belt may break, causing catastrophic engine damage. A broken timing belt typically causes the valves to hit the tops of the pistons, bending the valves and/or destroying the pistons. A broken timing belt can indeed lead to the complete destruction of the engine.

     To avoid this fate, replace the timing belt every 60,000 miles or every four years. If you live in a dry climate (like Arizona), or if you don’t drive your car often, then I recommend replacing the belt more often. In dry climates, belts can become brittle and worn much more quickly. If your car sits for long periods of time, the belts take on the bends and shapes of the pulleys while the car is parked. Both circumstances increase the likelihood of belt failure.

     Jack the car up to gain easier access to the crankshaft pulley and lower radiator hoses; it will also be easier to remove the coolant. Be sure to place the transmission in neutral so you can turn the engine more easily. Also remove the spark plugs, as this will make it easier still to turn the engine—and to recognize any interference problems when you install the new timing belt.

     Although it’s not necessary, it’s wise to inspect and/or replace the water pump and thermostat at this time (see Project 35). As a rule, replace the water pump every second time you replace the timing belt.

     E30 cars manufactured in 1986 and later years should have a tensioner marked with “Z 127.” If your tensioner does not have this code, replace it with one that does. This tensioner design replaced an earlier, potentially faulty, design.

     Follow the procedure documented in the photos for detailed instructions on removing the timing belt and camshaft sprocket. Reinstall the tensioner before you install the new belt. To reinstall the tensioner, compress the spring as far as you can, and then temporarily tighten the adjustable tensioner bolt (green arrow, Photo 12). When you install the new timing belt, place it on the engine, working counterclockwise, starting from the crankshaft sprocket. Slip the belt over the intermediate shaft sprocket, around the tensioner, and over the camshaft sprocket. Now, loosen both bolts on the tensioner to apply tension to the timing belt. Verify that the timing marks for TDC on the camshaft sprocket match up with the notch on the cylinder head (see Photo 10). With a socket on the crankshaft pulley, carefully rotate the engine clockwise through two complete revolutions (720 degrees). Verify that the timing mark on the camshaft pulley is in place again. Torque the upper and lower tensioner mounting bolts to 22 N-m (16 ft-lbs).

     With the tensioner in place, reinstall the crankshaft pulley and lower timing belt cover. Recheck that the camshaft sprocket is aligned with the cylinder head when the vibration damper or toothed timing wheel O/Tmark is aligned with the lower timing belt cover. If not, remove the damper and lower timing belt cover and reposition the belt. Reinstall the front pulley, applying red Loctite to the six mounting bolts.

     When you’re finished, reinstall the radiator and bleed the cooling system as described in Project 33.

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Figure 1

Shown here are the items included with the E30 timing belt kit available from PelicanParts.com and a few other items I recommend replacing. In addition to a complete set of radiator and coolant hoses, this photo shows: A: Air conditioning, alternator, and power steering belt. B: Water pump. C: Timing belt. D: Timing belt tensioner. E: Thermostat. F: Camshaft seal and O-ring. Complete coolant hose set (perimeter)

Figure 2

This photo shows the engine compartment of a 1987 E30 325e engine compartment. Although not required when changing the E30 timing belt, I recommend that you also adjust the valves. I have removed the valve covers in this photo for that purpose, but their removal is not required to replace the timing belt. Although you could probably replace the timing belt with the radiator in place (yellow arrow), I do not recommend it. Removal is a snap and makes the job a whole lot easier. Begin by disconnecting the upper radiator hose (blue arrow) and the radiator overflow hose (red arrow).

Figure 3

With a large bucket and paper towels handy, remove the plug on the bottom of the radiator and disconnect the lower radiator hose (yellow arrow). If you replace the coolant (recommended), pull out the plug on the engine block and remove the coolant from the block. Dispose of the coolant properly—it is toxic to children and small animals. Also verify that the engine is cold. When you disconnect the lower hose, you will spill some of the coolant, and you don’t want to burn yourself.

Figure 4

With the radiator hoses removed, turn your attention to the radiator mounts, on the left and right sides of the radiator. Remove these mounts with a 10-millimeter socket (blue arrow). Inspect the mounts when you remove them; in most cases the rubber will be deteriorated and require replacement (yellow arrow). The photo inset shows the radiator coolant temperature sensor that also must be removed prior to pulling out the radiator.

Figure 5

Shown here is the front of the engine after the radiator has been removed. At this point, the fan and fan pulley have been removed (see Project 34 for removal instructions). The belts have also been cut off with shears (you should replace them anyway). The yellow arrow shows the front of the distributor cap. The green arrow points to the air conditioning compressor. The blue arrow shows the alternator. The red arrow points to the water pump pulley. The orange arrow shows the main crankshaft pulley, and the purple arrow points to the power steering pump.

Figure 6

Here’s a close-up of the alternator and its supporting brackets. You need to remove this bracket in order to remove the timing belt cover. First, loosen the rear alternator bolt, indicated by the green arrow. Do not turn the front alternator pinion bolt until the rear nut is loosened. With the bolts loose, remove the nut that holds the bracket to the timing belt cover (yellow arrow) and swing the bracket out of the way. It’s also a good time to remove the crankshaft sensor—simply pull it out of its bracket.

Figure 7

Now remove the distributor cap, which is held on with three small bolts. With the cap removed, you can remove the distributor rotor. Use a 3-millimeter Allen wrench or driver for this task. Replace the cap and rotor with new ones when replacing the timing belt.

Figure 8

At this point, you should be able to remove the few small bolts that hold on the upper timing belt cover. The cover will slide off, and you should see the upper part of the timing belt. The red arrow indicates the camshaft timing sprocket, while the green arrow indicates the timing belt tensioner. If you plan to replace the camshaft seals (recommended), skip ahead to Photo 14, but loosen up the Torx bolt on the camshaft sprocket before you remove the timing belt. If you accidentally rotate the camshaft when the belt is off, you may bend the valves by pushing them into the pistons.

Figure 9

Place a deep 22-millimeter socket on the center of the crankshaft pulley and rotate the engine until it reaches top dead center (TDC) for cylinder number 1. At TDC for cylinder number 1, the O/T mark on the crankshaft pulley timing wheel or vibration damper (green arrow) will line up with the line on the lower timing belt cover (yellow arrow). In addition, the mark on the camshaft sprocket should line up with the mark on the cylinder head. Since this is a four-stroke engine, the TDC setting in the photo may also indicate that the engine is at TDC for cylinder number 6. Check the camshaft sprocket to make sure (see Photo 10).

Figure 10

When setting the timing, it’s very important to verify that the engine is set at top dead center (TDC) for cylinder number 1, indicated by the marking on the crankshaft and the camshaft sprocket as pictured The green arrow shows the thin line on the sprocket that must match the corresponding mark on the cylinder head (yellow arrow). These two marks should line up, along with the mark in Photo 9. Only when these marks are aligned should you remove the timing belt.

Figure 11

The front pulley (also called the three-in-one pulley) is held on with six bolts (green arrow) that can be nearly impossible to see without a mirror. Remove these bolts prior to removing the front pulley. Use a 22-millimeter deep socket and a breaker bar to hold the crankshaft steady while you loosen and remove the bolts with a socket driver. After you get the bolts off, you should be able to pull the front pulley off of the crankshaft. Behind this pulley is a vibration damper (a mini-flywheel) that also pulls off the crankshaft (a toothed timing wheel is behind the pulley on later cars). You may need to employ extensive wiggling or a rubber mallet to budge the damper/timing wheel from its home position. With the pulley and damper/timing wheel removed, you can now remove the lower timing belt cover.

Figure 12

This collection of photos shows the removal of the timing belt tensioner. Mark the location of the main tensioner bolt (the one that fits through the slot) so you can approximate its location when you reinstall it. Using a wrench, remove the bolt that holds the tensioner, timing belt cover, and alternator bracket (inset, upper left). Then remove the main adjustment bolt for the tensioner (green arrow, lower left inset). With the bolts removed, you should be able to remove the tensioner and tensioner spring.

Figure 13

It’s easy to slide out the timing belt once the lower cover has been removed and the tensioner has been disconnected. This photo shows the crankshaft pulley at the bottom and the intermediate shaft pulley off to the right.

Figure 14

I recommend you remove the camshaft sprocket so you can replace the two seals located behind it. These seals tend to deteriorate with age and cause leaks. Replace them when you have relatively easy access to them. Remove the camshaft sprocket with a T-50 Torx socket. Use a screwdriver propped up against the cylinder head to gently hold the sprocket in place while you remove the Torx bolt. Don’t allow the camshaft to turn, as you could cause the valves to accidentally hit the pistons.

Figure 15

Shown here are the two camshaft seals that I recommend replacing while you have access to them. There’s a small O-ring that fits into the cylinder head (green arrow) and a spring-seal that fits around the rotating end of the camshaft (red arrow). Replacement of these seals is similar to the replacement of the flywheel seal (see Project 44).


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Pelican Technical Article:

BMW E30 Timing Belt ReplacementWayne R. Dempsey

BMW E30 Timing Belt
Replacement
Wayne R. Dempsey