Checking/adjusting valve clearances (BMW 5 Series E34)

To check and adjust valve clearances, the following special tool is required:

• A set of feeler gauges with a resolution of 0.05 mm.
• A piece of wire about 2mm thick (or a thin drill).
• Set of wrenches and set of heads.

The following wearing parts are required:

• Cylinder head cover gasket.

To compensate for thermal expansion in the valve train, a certain clearance must be provided between the camshaft lobes and the valves or rocker arms. Valve clearances change over time due to valve shrinkage and wear of the valve train.

If the clearance is too small, the valve timing changes, compression deteriorates, engine power decreases, and the engine runs unevenly. In extreme cases, valves may become deformed or valve seats may burn out. If the clearance is too large, strong mechanical knocks occur, valve timing changes, engine power decreases due to the reduced valve opening time and thus worsening cylinder filling, and the engine runs unevenly.

Checking and, if necessary, adjusting the valve clearances should be carried out on all engines except models 518i, 525td/tds, 520i/525i manufactured since May 1990 according to the indications of the service interval indicator or as part of the maintenance every 20,000 km. The mentioned engines have hydraulic valve clearance compensators and do not require their checking or adjustment.

Examination

Checking and adjusting valve clearances is performed both on a cold and a warm engine.

Remove the cylinder head cover.

There are two options for turning the engine to the desired position. The first, simplest option: engage 4th gear, release the handbrake. Move the car.



Option 2: Move the gearshift lever to neutral, tighten the handbrake. Turn the engine clockwise using the central bolt of the crankshaft belt pulley, installing a 27/30 mm wrench on it (direction of engine rotation). At the same time, the camshaft also rotates.

It is advisable to start checking with the valves of the 1st cylinder, setting it to the top dead center position. The 1st cylinder is located at the front of the engine. After this, the engine is turned further (on a four-cylinder engine by half a turn) and the valves of the next cylinder are checked in accordance with the ignition sequence.

Firing sequence on a four-cylinder engine: 1-3-4-2; on a six-cylinder engine: 1-5-3-6-2-4.



Another option for adjusting valve clearances: turn the engine to a position where the camshaft cam of any valve is facing away from the rocker arm of the valve being checked, and the cam is adjacent to the rocker arm with its generatrix. The figure shows a gasoline engine; on a diesel engine, the cam should be moved away from the rocker arm. In this position, measure the valve clearance and adjust it if necessary.



Mark the rocker arm with a marker.

Move the car a little further until another cam moves away from the rocker arm. In this case, the sequence of adjusting the valve clearances is irrelevant. The rocker arms are marked so as not to check the valve clearance again by mistake.



Petrol engines: Measure the valve clearance with feeler gauge F inserted between eccentric E and the end of the valve stem.



Diesel engines 524td: Measure the valve clearance with feeler gauge F between the cam and the rocker arm.

The valve clearance is adjusted correctly if the feeler gauge fits tightly.

For testing, take a feeler gauge with a specified size exceeding See Table 1 by 0.05 mm. It should not enter between the valve and the rocker arm. If it passes, reduce the valve clearance.



Table 1. Valve clearances

Note: The specified clearance values for the intake and exhaust valves are the same.

"Cold" is the engine when the coolant temperature is below +35°C. To adjust the valve clearances on a "warmed up" engine, the coolant temperature should be around +80°C. A sign is a warm lower water hose of the radiator. The thermostat just opens the large circuit of the coolant circulation.

Adjustment

(Figure W - 6266) If the valve clearance differs from the specified value, insert the BMW rod 113070 into the hole of the eccentric E, loosen the nut and turn the eccentric with the rod until the specified valve clearance is reached. If the BMW tool is not available, a thin screwdriver of the appropriate diameter can be used.

Tighten the lock nut to a torque of approximately 10 Nm (estimated value), holding the eccentric. Check the valve clearance again and turn the engine further. Check or adjust the clearances of the remaining valves in the same way.

Install the cylinder head cover.

[The article text was copied from an online resource: «BMWMAN.RU»]