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MERCEDES-BENZ |
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We
offer a reliable and prompt delivery service
OM 636 HISTORY Numerous automotive
applications include the Mercedes-Benz Unimog 2010, 401, 402 and 411 models and
the 319 series transporter as well as in forklift trucks, farm tractors,
combine harvesters and other special purpose vehicles. The OM 636 was also used to power
electrical generators and stationary water pumps. Readily marinised by
fitment of a heat exchanger and sea-water cooling system, the OM 636 is
popular in many yachts and cruisers throughout the world. Over the years, it has earned an enviable
reputation for economy and durability which contributes to its continuing
popularity with boat owners in the 21st century. During the 1960s, 70s
and 80s, the OM 636 was marinised by a number of specialist firms throughout
Europe. Among them Wizeman
WM-36 (Germany), Volvo Penta MD4 (Sweden), Renault
RC40D (France), Solé Diesel SM-636 (Spain) and Nannidiesel 4.180 (Italy/France). In the UK, the 42 HP
OM 636 was marinised and fitted with a Bowman heat exchanger and a
belt-driven Jabsco sea-water pump. After the end of
production in Germany, the engine continued to be manufactured under licence in Spain - a testimony to the successful original
design. Perhaps the most recent
application of the OM 636 was in Thermo King refrigeration units fitted to
trucks transporting perishable goods. OM 636 TECHNICAL DESCRIPTION The cast iron
crankcase has integral cylinders with a standard bore of 75mm. Re-boring is possible up to a maximum bore
of 77mm. Pistons are available in 4
repair sizes. It is also possible to
reline the block back to standard bore. The injection pump and
oil filter are located on the right hand side of the engine (as seen from the
flywheel end). The generator, starter
motor, oil dipstick and breather pipe are on the left. At the front, an alloy timing cover
encloses helical gears driving the camshaft and injection pump off the
crankshaft. A side cover seals the
valve lifter chamber. The alloy oil
sump is bolted to the crankcase. The cast iron cylinder
head is fastened to the crankcase by hexagon-head bolts. A composite cylinder head gasket seals the
combustion chambers and water passages between the head and the
crankcase. The cylinder head features
removable precombustion chambers into which injectors atomize the diesel fuel
for combustion. Pre-heater plugs are used as a starting aid. An alloy rocker cover with an oil filler
seals the top of the cylinder head. The 3-main bearing,
drop-forged crankshaft has hardened bearing surfaces. The centre bearing serves as the thrust
bearing. Counterweights on the crankshaft
compensate for the rotational inertia in relieving the forces on the main
bearings. The coolant pump is driven
by a 'V' belt pulley fitted to the front of the crankshaft. The forged steel
connecting rods are equipped with bronze bushes at the small end to
accommodate the piston pin and a 2- piece friction bearing at the big
end. The bearing cap is secured to the
connecting rod by 2 special bolts and nuts. The alloy pistons
generally feature 3 compression rings and 2 oil scraper rings. The floating piston pin is retained by circlips. The
piston crown is dished. The drop-forged
camshaft with hardened bearing surfaces and cams is supported by 3 alloy
bearings in the crankcase. Axial
movement is controlled by the front camshaft bearing which together with the
2nd camshaft bearing is of a split design. Each cylinder features
an overhead exhaust and inlet valve opened and closed by the camshaft by
means of mechanical lifters, pushrods and rocker arms. The fuel lift pump is
mounted on the injection pump and draws fuel from the tank. It incorporates a
hand primer pump that is used the bleed the fuel lines of air (e.g. after
filter replacement). Diesel fuel is
fed to the injection pump after passing through a filter. The injection pump delivers fuel under
pressure to the injectors via rigid injector pipes of equal length. On engines fitted with BOSCH injectors
excess fuel is returned to the fuel tank by a metallic spill pipe
interconnecting the injectors. A
flexible fuel spill hose is used on engines fitted with TDZ injectors. Depending on
application, the injection pump is fitted with a pneumatic or centrifugal
governor that controls the amount of fuel injected according to engine
load. On engines producing the maximum
42HP an automatic timing device advances the timing of the pump with
increasing engine speed. Engine lubrication is
provided by an oil pump driven by the camshaft. Oil is drawn from the sump and directed
into the main oil gallery after being filtered by a fine mesh strainer or cartridge-type
filter. Oil is fed to the crankshaft
and camshaft bearings via small bores.
From the front camshaft bearing, oil continues to the rocker shaft
pedestals and cylinder head through external oil lines. The rocker arm
bearings and pushrods are lubricated by oil flowing through hollow rocker
shafts. Cylinder bores, piston pins
and timing gears are splash-lubricated.
Two pressure relief valves are fitted to the oil circuit. The main circuit features a relief valve
that opens at 8 bar, protecting the engine against excessive oil
pressure. The oil filter is equipped
with a valve that opens at 2 bar allowing oil to by-pass the filter should it
be clogged. Most installations feature
an electrical or mechanical gauge to monitor the engine's oil pressure. The injection pump and
cooling water pumps have their own oil supply and are not connected to the
main engine lube circuit. However,
modern replacement water pumps feature sealed-for-life bearings and require
no maintenance. Engine temperature is
controlled by means of a belt-driven coolant pump, a radiator or heat
exchanger and a thermostat. RECONDITIONING AN OM 636 ENGINE Engines to be
reconditioned should be completely disassembled and chemically cleaned, the
engine block and cylinder head pressure-tested and oil galleries
cleaned. Any damaged studs on the
block or head should be renewed. Cylinders must be bored
and honed to accommodate new pistons. Crankshafts checked, reground and
polished. All crankshaft and camshaft
bearings should be systemically replaced.
The camshaft and timing gears checked and replaced if necessary. A new oil pump should be fitted before
mounting the sump to the crankcase. Cylinder heads must be
refaced within given limits and the valve seats reworked to ensure the
correct valve height. Ensure that the
latest valve guides are fitted. These have
an external annular groove for a valve stem seal to be fitted. Inlet and exhaust valves should be replaced
if necessary. When disassembling the
cylinder head, the precombustion chambers should be removed and bead blasted for
thorough inspection. Removing these
pre-chambers can be a tricky procedure without special tools but it is
strongly recommended since they are invariably coked up. Attention should be
paid to the condition and wear of all valve train components especially on
high mileage engines e.g. valve lifters, pushrods, rocker arms, adjustment
screws and rocker shafts. Rocker
shafts usually show signs of wear and scoring and should be replaced. The lubrication of the rocker shafts is
assured by the external oil lines and these should be carefully checked or
replaced if in poor condition. Whilst the core engine
is being rebuilt, it is advised to have the diesel fuel injection pump and the
injectors checked and recalibrated by a competent diesel engineer. New gaskets and seals should
be used throughout the rebuild. If facilities are
available, rebuilt engines should be run on a dynamometer for several hours
to confirm power output, oil pressure and exhaust emissions. The engine can now be completed
with its external ancillaries according to its specification and
application. Marine engines will
require the fitment of a heat exchanger, sea water pump, starter motor,
alternator, hoses and pipe work. All
these components will need to be checked, reconditioned or replaced. In order to protect the
engine from external corrosion, especially important in a marine environment,
completed engines should be degreased, etch-primed and painted prior to installation. This will then result
in a ready-to-fit marine engine. OM 636 SPARE PARTS AND REBUILD KITS Our stocks include: ENGINE CRANKCASE,
FRONT COVER AND OIL SUMP Full engine gasket
sets CYLINDER HEAD De-coke cylinder head
gasket sets Valve guides CRANKSHAFT AND
PISTONS Crankshaft main
bearings: standard and all undersizes TIMING EQUIPMENT Camshafts DIESEL FUEL
INJECTION EQUIPMENT Reconditioned BOSCH
PES4A50 fuel injection pumps FUEL FILTER Fuel filter elements MANIFOLDS Inlet manifold casting
ELECTRICAL
EQUIPMENT Series and Parallel
'Fast-Start' glow plugs ENGINE LUBRICATION Oil pumps ENGINE COOLING Fresh water pumps with
fitted pulley Coolant vent line kits MARINISATION PARTS Vacuum pipes from
injection pump governor to throttle body Engine oil cooler kits
A copy of the original
operating and service instruction booklets is available together with a parts
illustration catalogue showing exploded view diagrams of the engine
components. To receive a
compilation of technical and parts bulletins for this engine, please send a
message indicating your email address. So whether you need a
gasket or an engine rebuild kit - contact us to discuss your requirements. Nous parlons
français. Wir sprechen
deutsch. |
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