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MERCEDES-BENZ |
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We
offer a reliable and prompt delivery service
OM 636 HISTORY Its design was derived
from the M 136 petrol engine fitted to the earlier 170V and with which it
shares many dimensional similarities and internal components. Numerous automotive
applications of the OM 636 include the Mercedes-Benz Unimog 2010, 401, 402
and 411 models, 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 excellent fuel economy and durability which contributes to its
continuing popularity with boat owners in the 21st century. During the 1960s, 70s
and 80s, the 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 as shown in the
picture above. 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 low pressure of this fuel feed to the
injection pump is regulated by a pressure relief valve fitted on the fuel
filter head. The injection pump delivers fuel under high 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. Engine blocks that
were not originally fitted with liners should be bored out and honed to the
next repair size up to a maximum bore of 77mm. Blocks fitted with liners can be bored to
the 1st repair size 75.50mm or the liners replaced. 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 to fit a valve stem seal. Early engines do not have a valve stem seal
but feature a valve spring retainer with an extended sleeve. 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 NEW SPARE PARTS AND REBUILD KITS
Our stocks include: ENGINE CRANKCASE,
FRONT COVER AND OIL SUMP Full engine gasket
sets CYLINDER HEAD Reconditioned cylinder
heads CRANKSHAFT AND
PISTONS Crankshaft main
bearings: standard and all undersizes TIMING EQUIPMENT Camshafts DIESEL FUEL
INJECTION EQUIPMENT Reconditioned BOSCH
diesel fuel injection pumps FUEL FILTER Fuel filter elements We also offer a
replacement fuel filter assembly featuring a screw-on disposable filter which
can be replaced without detaching the filter head from its mounting. It can be specified for remote fitment to a
vertical or horizontal mounting surface.
MANIFOLDS Inlet manifold for
marine engine ELECTRICAL
EQUIPMENT Modern 'Fast-Start'
glow plugs to be wired in parallel ENGINE LUBRICATION Oil pumps The original oil
filter assembly on the engine can be replaced with a modern replaceable
spin-on filter fitted at a convenient location in the engine
compartment. Enquire for further
details. ENGINE COOLING Fresh water pumps with
fitted pulley MARINISATION PARTS Vacuum pipes from
injection pump governor to throttle body OM 636 engines
marinised by Nanni were fitted with either a Nanni or a BOWMAN heat
exchanger. Although external parts
specific to the Nannidiesel heat exchanger fitment
are no longer available, it is possible to re-marinise
the engine by fitting a new Bowman heat exchanger together with the
associated pipe work. Please contact
us for more information. 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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WESTFIELD |
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Click below to see
an OM 636 engine sitting on a testbed |
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