Blue Smoke At Idling and After Operation on the Overrun
Cause / Remedy:
a) Engine emits blue smoke, stops when engine breather hoses left and right are pulled off. Throttle valve is oily.
Too much oil in the cylinder head cover, oil is sucked to the idling air distributor (left) or the, air cleaner (right) via the baffle plate, also when driving up or down hill, at high speed or during braking.
1 Check oil baffle plate in the cylinder head cover left and right. Plate may not be positioned at the side or the rivet has come loose. Renew valve cover.
2 Check camshaft lubricating tube for proper seating. Connection pieces may have come loose on the camshaft bearing pedestal. Renew connecting pieces.
3 Check oil return; pour oil into the oil return bore in front of the last camshaft bearing bracket. The oil should drain without undue delay. If oil does not drain at the left and right, the casting skin in the crankcase (see arrow in the picture) must be removed; for this purpose remove transmission and oil pan. If oil fails to drain on one side only, it may be necessary to remove a foreign body in the return gallery cylinder head/crankcase.
b) Engine smokes blue, even if engine breather hoses left and right are disconnected.
For diagnosis, run engine at operating temperature for approx. 5 minutes at 3000/m in. Subsequently operate the engine on the overrun, so that the high vacuum will suck in the oil from the leaks. From the operation on the overrun, switch off engine. In order to avoid as far as possible false diagnoses caused by fuel, wait for 10 minutes after switching the engine off, then inspect
1. Diaphragm of the modulating pressure vacuum unit is torn. Oil is drawn in by the automatic transmission. 4th cylinder and spark plug are oily. Oil runs out of disconnected vacuum line on the modulating pressure unit. Piston or connecting rod of 4th cylinder may be damaged.
Renew modulating pressure unit.
2. Valve stem seals are missing or not correctly installed. Occasional faulty valve seals (white color) with the sealing collar (see Fig.) shifted up or down, may be installed up to production of May 1981.
These valve stem seals are forced down with running engine. On inspection, valve cones and inlet or exhaust port are moist and oily.
Renew valve stem seals on inlet and exhaust valves.
Dimension A
Nominal 2.0 - 2.2 mm
3. Valve guides in cylinder head are loose, basic bore in cylinder head is oval. Usually associated with noise, blue smoke also when engine is cold.
Upon inspection, valve cones as well as inlet and exhaust port are moist and oily.
Renew valve guides. Check basic bores in cylinder head.
4. On chromed valves, the chromium layer is faulty or the valve stem is below minimum diameter in the area of the valve stem seal. Upon inspection, valve cones, inlet and exhaust port are moist and oily.
Renew valves and valve stem seals (see remedy point 2).
5. Excessive valve play in the guides, valve stem seal moves on the valve guide due to a worn out retaining groove. The valve can be moved horizontally in the guide.
Some play in the valve guides is present already after a relatively short running period and there fore without consequence. The new elastic Viton valve stem seals (black color) adapt to the relative movements of the valves and have a better sealing effect than the previously used Teflon valve stem seals (white color) (see remedy point 2).
Valve cones, inlet or exhaust port appear moist and oily during inspection.
Renew valve guides, valves and valve stem seals.
6. Oil runs via piston and piston rings Oil collects on the piston crown and adheres to the cylinder wall. Axial piston ring play is excessive. Piston rings are damaged or have abnormal wear, pressure loss is normal however. Spark plug is wet with oil.
Piston rings may also be worn in individual cylinders.
Pistons, piston rings have seized, severe score marks noticeable in the cylinder wall, possibly cracked cylinder.
Remove cylinder head to diagnose. Remove piston and refit with new piston rings Order piston ring sets from plant 50 (PEW Sindelfingen), specifying the piston code number.