M104.98x
This 3.0 L (2960 cc) 24v DOHC was introduced as a sports car resp. top model completing the line-up of M103 12V engines. M103 and this engine were replaced by the later 2.8l and 3.2l versions of M104. It was found in the W124 300E-24 models, C124 300CE-24 models, T124 300TE-24 models and R129 300SL-24 models. The 3.0 L M104 produced 217 hp (162 kW) to 228 hp(without catalytic version) and features KE-Jetronic fuel injection, cylinder specific ignition-timing, variable valve timing and under-piston cooling jets. 1)
Engine Oil
Filters
M104 engines use a cartridge filter and can be ordered from the dealer using part number 104 180 01 09, but aftermarket kits can be purchased from automotive retailers referencing the table below. Kits should come with a new seal ring for replacement on the filter cap.
Filters
Brand | Part number |
WIX | 51145 |
K&N | PS7008 |
MicroGard | MGL51145 |
ACDelco | PF2146 |
Bosch | 72194WS |
Mann | HU7271X |
Fluid
A list of compatible fluids for this engine can be found within the 229.3 oil specifications. Engine oil capacity including filter requires 7.0 liters of oil. Use the chart below as a guideline for choosing correct oil weights.
Compression Pressure Test
Warm engine to operating temperature
Remove ignition coil wire to distributor
Remove spark plug
Insert compression pressure measuring device into spark plug
Crank engine for at least 8 revolutions
Read value and reinstall spark plug
Repeat for all cylinders
Taking a measurement on the compression tester
Cylinder Head
Removal
Disconnect battery
Drain coolant at radiator and engine block
Remove exhaust manifold
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Remove upper timing cover
Remove guide pin rail with extractor
Use washer/bolt as a makeshift puller. Thread size is M6x1.0
Remove timing chain tensioner
Remove exhaust camshaft chain gear, T30
Remove lower guide sprocket, left handed thread 17mm
Pull chain off the intake camshaft gear and set aside
Unbolt cylinder head in reverse of tightening order with the following 3 stages (M12 triple square socket)
90 degrees starting with bolt #14 → #1
90 degrees starting with bolt #14 → #1
Unscrew and completely remove bolt starting with #14 → #1
Loosen water pump hose
Lift cylinder head out
Use an M6x1.0 screw to extract the guide rail pin
Cylinder head tightening order
Prepare for install
Cylinder Head
While the cylinder head is off, it's recommended to send it off to a machine shop to have the mating surface refinished and the valve stem seals replaced at the very least. Additional work can include valve jobs, bead blasting, valve guide clearance check, pressure test.
Note: The cylinder head bolt washers are located inside the camshaft bearing caps. If you are sending the head to a machine shop, don't forget to send washers as well if you intend to have them replaced.
Engine Block
The mating surface of the block where the head gasket sits must be thoroughly cleaned. A carbide scraper such as a Bahco 625 works great here. Otherwise a flat razor edge can also work as well.
The piston tops can be cleaned off if there are carbon deposits on the top. Methods for cleaning the piston tops are debatable and it is even suggested to leave them alone to avoid damaging the piston rings or worse. The damage occurs when either the carbon deposits or abrasive materials (aluminum oxide from maroon Scotch-Brite pads, silicon carbide from grey Scotch-Brite pads) fall down the cylinder walls and rest on top of the piston rings. Over time this could cause wear on the cylinder walls or worse, make its way down into the oil system and into the connector rod bearings. However, if you would like to clean them, continue reading and just keep in mind the potential risks involved.
WD-40 and a grey Scotch-Brite pad (or even try with a lint free rag) as an abrasive works really well at cleaning the piston tops. Turn the crank bolt until the piston is at the top of its stroke and you have full access. Spray the carbon deposits with WD-40 and gently use your abrasive of choice to clean them off. Wipe down the area with a lint free towel or rag. Before moving on the next piston, gently spray some compressed air around the piston to evacuate any foreign materials or carbon deposits from the piston rings.
Piston tops and mating surface before cleaning
Piston tops and mating surface cleaned
Installation
Fit head gasket onto engine block
Lower cylinder head onto engine block
Oil cylinder bolt threads and head mating surface and torque bolts in 3 stages following the tightening order.
Stage 1: 55 Nm
Stage 2: 90 degrees
Stage 3: 90 degrees
It is helpful to mark the bolt with a small dab of paint at the 12 o'clock position after stage 1 to keep track of how many degrees the bolt has turned.
Setup basic timing
Install timing chain guide sprocket. Tighten to 35 Nm, reverse threaded.
Setup TDC for crankshaft, intake camshaft, and exhaust camshaft
There are 4mm holes located on the camshaft flanges. Stick a 4mm allen or a 5/32 drill bit in the hole and align camshaft until the hole is flush with the surface of the head
Rotate intake camshaft gear clockwise until stop. This puts the camshaft in retarded position.
Pull chain up and over the intake camshaft
Install exhaust camshaft sprocket with chain
Avoid turning and checking the timing until after the upper timing cover and chain tensioner are both installed. Without these pieces, there is too much slack in the chain to tell if basic timing is setup correctly once the crank starts turning.
Install guide rail pin
Install upper timing cover with guide rail
Install chain tensioner
Check timing by rotating the engine through one entire combustion cycle. Check alignment of camshafts and crankshaft.
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Install exhaust manifold
Head gasket installed
The M104 cylinder head is very heavy. A hoist is used to lower the head onto the block safely.
Cylinder head tightening order
Mark on cylinder head bolt to estimate torquing stages
Intake camshaft set to TDC
Complete Engine Removal
Optional: Remove front bumper for extra clearance for shorter reaching engine hoists
Optional: Remove alternator for extra clearance when pulleys are interfering with cross member
Optional: Remove transmission cooler lines for extra clearance when the lines interfere with cross member
Optional: Drain engine oil. (Task is easier to manage when motor is still in a car chassis)
Remove bottom engine tray
Remove air cleaner box
Remove radiator
Remove viscous fan clutch assembly
Power Steering
Drain power steering reservoir
Remove suction pipe
Remove high pressure pipe
AC
Remove poly v-belt
Remove air compressor with hoses still attached
Remove condenser
Disconnect fuel pipes at fuel distributor
Disconnect accelerator cable and transmission bowden cable
Disconnect heater supply and return hoses
Disconnect vacuum lines by brake booster, to transmission, to EZL unit, EGR pipe, and smog pump
Disconnect brake booster line at intake manifold
Electrical connections
Disconnect oil pressure sensor and oil level sensor
Disconnect main engine wiring harness
Disconnect crank position sensor and knock sensor at EZL
Disconnect TD signal at X11 and unbolt X11 connector from fender
Disconnect starter bracket at rear of intake manifold
Disconnect ignition coil from distributor
Unplug alternator
Unplug smog pump
Exhaust system
Disconnect down pipes from manifold
Unbolt support bracket on transmission
Automatic Transmission
Remove transmission mounting plate
Disconnect speedometer cable at transmission rear
Disconnect ground cable at bell housing
Disconnect kickdown solenoid
Disconnect starter lockout wire
Disconnect transmission overload
Disconnect shift rod
Disconnect flex plate from transmission output flange
Unbolt motor mounts from underneath
Secure engine with hoist and remove engine with transmission attached
Unplug starter wires as engine is being lifted
Remove fuel cooler mounting bracket from block
Fan shroud
Removal / Installation
Remove locking pin (18)
Rotate fan shroud ring (6) to open position and separate
Remove retaining spring clips (15)
Lift fan shroud and fan shroud ring to remove
Install in reverse procedure
Fan clutch
The M104.98x engines share the same fan clutch as the older M103 predecessor. The part number for the viscous fan clutch is 103 200 04 22
A special tool is required to counter-hold the fan clutch while loosening the 8mm allen hex bolt in the center. The part number for this tool is 103 589 00 40 00.
Removal
Remove fan shroud
Rotate fan with the 8mm allen hex bolt to align the counter-hold tool into a retaining hole behind the pulley.
While applying pressure on the counter-hold tool, loosen the 8mm hex allen bolt
Remove fan clutch and fan blade assembly together
Counter hold on the fan clutch
Removing fan clutch
Poly V-belt
Removal
Loosen 10mm allen hex bolt in center of belt tensioner
Loosen belt tensioner using 13mm adjustment from the top
Remove belt
Loosening main belt tensioner bolt
Loosening tension on belt
Installation
Route new belt according to diagram
Tension the belt using 13mm adjustment rod
Tighten until belt tensioner pointer is at max (leftmost)
Tighten 10mm allen hex bolt in center of belt tensioner to 75 Nm
Belt Tensioner
Removal
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Loosen bolts on pulleys for water pump, power steering pump, and fan clutch
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Remove pulleys on water pump, power steering pump, and fan clutch
Remove top bolt (6) of belt tensioner damper to front cover, 13mm hex
Remove center bolt to belt tensioner (16), 10mm allen
Remove 3 bolts on Y-bracket (1), (3), and (4) and remove Y-bracket
Note: Bottom right bolt (1) has counter-hold nut (2)
Remove setting pointer (13), belt tensioner (14), damper (10) and adjustment rod (18)
Installation
Install belt tensioner (14) with setting pointer (13), damper (10) and adjustment rod (18)
Align damper (10) and install top bolt (6), 13mm hex
Pointer set to lowest point (rightmost)
On Y-bracket, apply sealing compound on end that attaches to the fan bearing bracket. Apply to both front and rear of bracket.
Install bolts to 21 Nm, 13mm hex
Install center bolt to belt tensioner (16), 10mm allen
Do not tighten until belt tension has been set
Install pulleys on water pump, power steering pump, and fan clutch
Install poly v-belt
Install viscous fan clutch
Install fan shroud
Water Pump
Removal
Remove air cleaner
Drain coolant from radiator and engine block
Remove radiator
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Remove 13mm hex bolt holding power steering pump to rear belt tensioner bracket and set power steering pump aside with hoses connected
When this bolt is loosened, the sleeve for the upper belt tensioner bracket bolt will fall off.
Optional, but highly recommended for creating more space for accessing the upper right bolt
Remove idle air control valve
Remove dipstick
Remove heater return pipe
Remove thermostat cover and thermostat
Disconnect and remove sensors from water pump
Loosen hose clamp for short hose to cylinder head
Remove 10mm bolts on pipe to oil/water heat exchanger
Remove water pump bolts
Upper left - 6mm allen, accessible with 1/4 ratchet and a stubby 6mm allen socket
Bottom left - 13mm hex, accessible with 1/4 ratchet with extension and wobble 13mm socket
Upper right - 13mm hex, accessible with 1/4 ratchet with medium length extension and wobble socket from underneath the intake manifold
Bottom right - 13mm hex, accessible with 1/4 ratchet with long extension and wobble socket from underneath the intake manifold
Before pulling the water pump off, temporarily reinstall the dipstick if it was removed. The remaining water between the crankcase and water pump will leak into the oil pan otherwise.
13mm bolt behind power steering pump to remove
Power steering pump unbolted and set aside with hoses attached
Accessing the upper right bolt from underneath the intake manifold
Water pump removed
Installation
Apply small dabs of grease to the main seal to keep it in place during installation
Install smaller seal for oil/water heat exchange pipe
Bolt water pump to crankcase, torque to 25 Nm
Reconnect pipe for oil/water heat exchanger
Tighten hose clamp for short hose to head
Reinstall sensors
Reinstall thermostat and thermostat cover, replace seal.
Reinstall heater return pipe, replace seal.
Reinstall idle air control valve and dip stick if removed.
Reinstall the bracket that connects the power steering pump and belt tensioner
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Install radiator
Fill coolant, bleed, and check for leaks
Apply a little bit of grease just to hold the seal in place during install
Intake Manifold
Removal
Disconnect coolant hose and lifting hook at rear of cylinder head for clearance / maneuverability
Disconnect vacuum lines including brake booster
Brake booster: 19mm hex at intake manifold, 5mm allen at bracket
Disconnect all electrical plugs and move engine wire harness out of the way
Single pin connector that goes behind oil filter (need ID)
EHA valve and idle microswitch
Cold start valve, throttle position sensor (2), air intake sensor, and idle air control valve
Coolant temperature sensors (2), grounding bracket, AC compressor switch, AC pressure switch, and EZL plug
Coolant temperature sensor, camshaft position sensor, and camshaft advance solenoid
Disconnect fuel supply/return lines
Disconnect throttle linkages, bowden cable, and cruise control
Remove dipstick tube, 2x 10mm hex bolts
Disconnect crankcase breather hose between cylinders 2 and 3 on intake manifold
From underneath
Unbolt intake manifold mounting bracket located under cylinders 2 and 5, 13mm bolts
Disconnect EGR pipe, 22mm nut
Unbolt coolant pipe mount located behind (from underneath perspective) EGR pipe, 10mm
Unbolt starter wire holder, 10mm
Unbolt intake manifold bolts, 9x 13mm hex bolts
13mm bolt behind power steering pump to remove
Intake manifold bracket from underneath
Intake manifold installed with idle hoses
Mating surface
Fuel distributor
Removal
Disconnect fuel supply and return lines
Disconnect fuel pressure regulator mounting bracket, 10mm
Remove fuel injector lines at valve, 12mm nut, 16mm on the injector valve to counter
Including cold start valve
Remove 3 top screws, T25
Pull to remove
Vacuum System
Connection #35 in W124 vacuum diagram (117 078 03 81)
Connection #56 in W124 vacuum diagram
Connection #41-#38-#41 in W124 vacuum diagram
Connections #56 and #50 at rear of intake manifold
Upper timing cover
Removal
Remove valve cover
Remove distributor cap, rotor, mount, splash shield
Remove upper chain rail
Unbolt belt tensioner shock from timing cover
Optional: Remove idle pulley for clearance to the lower left timing cover bolt
Remove bolts for the timing cover and keep track of which bolts belong to which hole
Long 13mm hex bolts located upper right of timing cover for the lifting hooks
Shorter 13mm hex bolts located bottom left and bottom right nearest the u-seal
Pry cover off
Installation
The metal to metal surfaces of the upper timing cover need a sealant applied before installation. Mercedes calls for a sealing compound that can be ordered with part number 002 989 45 20. Alternatives include Loctite 5900 and Permatex The Right Stuff.
Loctite 5900
Permatex The Right Stuff
Mercedes Sealant
Clean mating surfaces of cylinder head, upper, and lower timing covers
Apply sealant in the corners of the mating surfaces
Install new rubber u-shaped seal and press the ends of the seal into the sealant
On the exhaust side, apply another small layer of sealant across the top of the rubber seal. This corner tends to leak at any opportunity it has.
Apply sealant to the mating surface of the timing cover. Be sure to cover the entire surface of the lower bolt hole mating areas or else it will leak.
Apply a light coat of motor oil to the top of the rubber u-shaped seal allowing the timing cover to slide on without folding the seal over
Assemble timing cover to cylinder head. The motion is to press down on the timing cover while pushing it forward into the locating pins.
Secure the bottom two 13mm hex bolts first while continuing to press down on the timing cover
Fasten the other timing cover bolts evenly and torque them to 25Nm
Mating surfaces on cylinder head and lower timing cover cleaned up
Close up of the problem corner where the 3 surfaces meet
Dab of sealant in the corner
Left side view of the installed U-shaped gasket
Right side view of the installed U-shaped gasket
Sealant applied to cover
The u-gasket after the upper timing cover has been installed
In addition to mounting the timing cover, the radial camshaft seal will need to be replaced. A special tool is required to install this seal properly
Insert tool into the end of the camshaft
Apply oil to the inside perimeter of the sealing hole and to the seal itself
Slide the seal onto the tool and press in
Remove the tool once the seal is no longer in contact with it
Tap the seal in with a socket until seal is flush with surface
If seal still leaks when flush with surface, then reinstall a new seal in a different position. A groove must have been worn at the previous location causing a leak.
Camshaft seal tool
Camshaft seal tool installed
Camshaft radial seal installed