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Lubricating system

Lubricating system


The engine lubricating system has forced-flow circulation, with the oil pressure being generated by a gear pump consisting of a pinion and an eccentric ring gear. The pump is located in the timing cover and driven by the crankshaft.

Oil is drawn from the sump to the oil pump via an inlet strainer and pipe. A reducing valve in the timing cover limits the oil pressure and returns surplus oil to the suction side of the pump. From the pump the oil then flows through a passage in the cylinder block to the oil filter.

Some cars are equipped with an oil cooler. On these cars, a thermostat in the oil-filter adapter housing opens at 80C (176F) to allow the oil to circulate through the oil cooler.

After filtering and cooling (via the oil cooler, if fitted), the oil is carried via a pipe to the main gallery in the cylinder block where the engine oil pressure sensor is located. If oil pressure drops too low the sensor grounds the circuit for the warning lamp on the main instrument panel, causing it to light up and alert the driver.

The crankshaft main bearings and big-end bearings are supplied with oil from the main gallery and via oilways in the crankshaft, while the pistons and cylinder walls are splash lubricated. Additionally, on turbo engines a piston- cooling nozzle is fitted at each cylinder to spray a fine jet of oil onto the underside of the piston.

The front bearing on the exhaust-side balance shaft is supplied with oil through a drilling from the No. 1 main bearing. The rear bearing on the exhaust-side balance shaft is supplied with oil through a drilling from the No. 3 main bearing. Both balance-shaft bearings on the inlet side are supplied with oil by the main gallery.

From the man gallery in the block, rising oilways to the cylinder head supply oil to the camshafts and tappets. Through one of the cylinder head bolt holes, oil flows through drilled passages to the camshaft bearings and valve tappets.

Oil sump


The oil sump is adapted to the cylinder block. Sealant (flange sealant, part no. 93 21 795) is applied directly to the flat surface of the flange.

Oil filter


The oil filter is located where it is readily accessible on the exhaust side of the cylinder block. An adapter housing is fitted between the oil filter and the block. Hoses run from the adapter housing to the engine oil cooler which is fitted on certain variants.