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MERCEDES-BENZ OM 636 |
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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 Readily
marinised by fitment of a heat exchanger and sea-water cooling system, the During
the 1960s, 70s and 80s, the In the After
the end of production in 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
NEW as well as reconditioned
cylinder heads CRANKSHAFT
AND PISTONS
Crankshaft
main bearings: standard and all undersizes TIMING
EQUIPMENT
Camshafts
DIESEL
FUEL INJECTION EQUIPMENT Reconditioned
BOSCH & TDZ 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 Alternator
with 80A output to replace standard unit 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 Engine
paint for brush or spray application 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 the latest edition of our technical and parts bulletins for this engine,
please send a message via email. 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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Click
below to see an OM 636 engine sitting on our testbed |
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