Difference between revisions of "M42"

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{{stub}}
 
  
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An engine found in all [[E30]] [[318iS]] cars and some early [[E36]] cars.
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=Characteristics=
 +
 
 +
 
 +
 
  
 +
 +
 +
 +
 +
The [[BMW]] '''M42''' is a 4-cylinder 16-valve engine, fitted to the [[318is]] as well as early [[E36]] models.
 +
[[Image:M42B18 Engine.jpg|thumb|600px|right|[[M42]] engine]]
 +
__TOC__
 
=History=
 
=History=
  
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In [[E30]] form it's twin cam 16v 4cyl 1796cc engine. It is a aluminium alloy engine which has  a relationship with the M1, M5 and M635CSi engines. The top of the rocker cover has a vapour/liquid separator which reduces oil consumption of the engine and bi-concave combustion chambers. Both very good examples why the M42 was state of the art at the time of production. The engine also has a duplex timing chain and a compression ratio of 10:1, which is similar to the duplex chain E30 M3 with a compression ratio of 10:5. The throttle body has two butterfly valves, a 35mm and 54mm valve. When you are lightly pressing the accelerator pedal, only the smaller valve opens but when you further depress your pedal the larger valve also opens. This enables the M42 engine to use less petrol when the car is on journeys which do not require constant change in speed. The inlet manifold is in two pieces, its design improves the low down torque of the engine. The engine also has hydraulic tappets which reduce the maintence of the engine. On every cylinder there is a coil pack which can be seen in the photo below (black item inside the wing next to the washer bottle) and is run on the Bosch Motronic injection system. The engine produces 136BHP at 6000RPM and 127 ft lbs of torque at 4600RPM, but the engine was then superceeded by the M44.
+
In [[E30]] form it's twin cam 16v 4cyl 1796cc engine. It is an aluminium alloy engine which shares a development history with the M1, M5 and M635CSi engines.  
  
−
The [[E36]] version adds a serpentine belt front pulley system and a different intake manifold. The M44 engine after 1995 was a 1900cc engine which produced 140BHP with 129 ft·lbf of torque and had a lowered redline of 6300RPM which is most commonly found in the E36 318iS
+
The M42 is the last chain-driven engine fitted to the E30, and the first 16-valve unit. It featured a number of innovations that made it a far more modern engine than any other fitted to the E30, including a twin-valve throttle body, coil pack ignition and bi-concave combustion chambers. This made the 318iS both an economical and performance model, with good power and torque characteristics.
  
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=Characteristics=
+
The engine also saw service in the [[E36]], which added a serpentine belt front pulley system and a different intake manifold. It was finally superseded in that model by the M44.
 +
 
 +
The engine produces 136BHP at 6000RPM and 127 ft lbs of torque at 4600RPM
  
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Dimensions (nominal) : 84mm/3.31" bore x 3.19" stroke
+
=Versions=
  
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Displacement : 1796 cc
+
{| class=wikitable
 +
|+'''Models'''
 +
|-
 +
!Engine!!Displacement!!Power!!Torque!!Redline!!Year
 +
|-
 +
|rowspan=2|M42B18||rowspan=2|1.8 L (1796 cc/110 in³)||101 kW (136 hp) @ 6000||175 N·m (129 ft·lbf) @ 4500||6300||1989-96
 +
|-
 +
|100 kW (134 hp) @ 5500||172 N·m (127 ft·lbf) @ 4500|| 6300||1989-96
 +
|}
  
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Camshaft : Duration: inlet 252 exhaust 252 Lift: inlet 10.2 exhaust 10.2
+
=Components=
  
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Lobe height: 1.8755-1.8803"
+
The engine in all E30s is a three-part design, featuring a main '''Block''' with a '''Sump''' at the bottom and a '''Head''' at the top.  
  
−
Con-rods : Max. weight variance without bearing shells: 4g/14oz split equally between big and small ends
+
==Sump==
  
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Crankshaft : End play: 0.0031-0.0064"
+
The M42 Sump is a two part design with an upper and lower sump. The upper part bolts directly to the [[M42#Block|block]], sealed with a [[M42#Sump_Gasket|gasket]], and the lower sump then bolts to the upper.
  
−
Thrust on cylinder 4
+
Leaks in this area are normally due to upper bolts coming loose, despite their torque rating. Because some of these bolts are only accessible with the lower sump removed, the two parts have to be disassembled to cure the leak. When removing the lower sump, don't be surprised to find a bolt sitting in the oil that has come out completely from the upper sump.
  
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Cylinders : Max. ovality: 0.01mm/0.0004"
+
===Oil Pump===
  
−
Max. taper: 0.01mm/0.0004"
+
===Sump Gasket===
  
−
Cylinder head : Height = 140mm/5.512"; minimum height = 139.55mm/5.494"
+
==Block==
  
−
Firing order : 1-3-4-2
+
The iron block is bored to 84mm. The cylinders have a maximum ovality of: 0.01mm/0.0004" with an identical maximum taper. Compression pressures : 10-11bar (143-156psi):
  
−
Fuel Pressure : 43 psi
+
===Crankshaft===
  
−
Oil pressure : 1.3-2.0 Bar/18 psi @ idle, 4.0-4.3 Bar/57-62 psi at 6250rpm
+
Crankshaft : End play: 0.0031-0.0064"
  
−
Oil Filter : Hengst E88H D24 in-bowl type
+
===Piston Rods===
  
−
Oil Type : I would recommend a 5W40, 5W50 or 10W50 fully synthetic (the text book says 15W50) as the tappets seem to prefer a lower viscosity oil
+
Con-rods : Max. weight variance without bearing shells: 4g/14oz split equally between big and small ends
  
−
Output : 134 (cat) -136 (non-cat) bhp @ 6000rpm; 127 ft-lb @ 4600 rpm
+
===Pistons===
  
 
Pistons : Clearance: 0.0004-0.0016"
 
Pistons : Clearance: 0.0004-0.0016"
Line 47: Line 66:
 
Piston rings : Gap: Top & bottom compression rings = 0.0080-0.0160" ; oil ring = 0.0080-0.0180"
 
Piston rings : Gap: Top & bottom compression rings = 0.0080-0.0160" ; oil ring = 0.0080-0.0180"
  
−
Compression pressures : 10-11bar (143-156psi):
+
Firing order: 1-3-4-2
  
−
Torques : Big ends: Step 1 = 23Nm/17 ft-lbs, Step 2 = +70 degrees
+
==Head==
  
−
Camshaft sprocket: 13-17 Nm/10-12 ft-lbs
+
The engine has hydraulic tappets which reduce the maintenance of the engine.
  
−
Camshaft bearing cap bolts: 13-17 Nm/10-12 ft-lbs
+
Cylinder head : Height = 140mm/5.512"; minimum height = 139.55mm/5.494"
  
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Crankshaft damper: 300-320 Nm/217-231 ft-lbs
+
===Rocker Cover===
  
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Cylinder head: Step 1 = 30-35Nm/22-25 ft-lbs, Step 2 = +90-95 degrees, Step 3 = +90-95 degrees
+
The top of the rocker cover has a vapour/liquid separator which reduces oil consumption of the engine and bi-concave combustion chambers.
  
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Exhaust manifold: 22-24Nm/17-18 ft-lbs
+
When removing and replacing the rocker cover, it is worth replacing the rocker cover gasket.
  
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Flywheel: 82-94 ft-lbs
+
===Cams===
  
−
Intake manifold: 13-17Nm/10-12 ft-lbs
+
Being a 16V engine, the M42 head features two camshafts; an Intake and an Exhaust.
  
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Main bearings: Step 1 = 20-25/14-18 ft-lbs, Step 2 = +47-53 degree turn
+
Camshaft : Duration: inlet 252 exhaust 252 Lift: inlet 10.2 exhaust 10.2
  
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Viscous fan coupling (LH threads): 40-50Nm/29-36ft-lbs
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Lobe height: 1.8755-1.8803"
  
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Timing chain tensioner: 23-27Nm/17-19 ft-lbs
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===Valves===
  
 
Valves : Seat angle: 45 degrees
 
Valves : Seat angle: 45 degrees
Line 85: Line 104:
 
Valve clearance : None, automatically compensated by hydraulic tappets
 
Valve clearance : None, automatically compensated by hydraulic tappets
  
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=Engine Bay=
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===Rocker Arms===
  
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[[Image:M42B18 Engine.jpg]]
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===Head Gasket===
  
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Identifying traits and points of interest in the above photo:
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===Timing Chain===
  
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*Individual coil packs
 
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*Twin-cam rocker cover
 
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*Twin-choke throttle (not-visible)
 
  
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=Servicing=
 
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''Main article: [[Basic_M42_Servicing|Basic M42 Servicing]]
 
  
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=Common Problems=
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===Breather Hose===
  
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==Profile Gasket==
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To balance the pressure inside the head, a rubber hose runs from the top of the [[Engines#Rocker_Cover|rocker cover]] to the [[M42#Throttle_Body|throttle body]].
  
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The most common problem with the 318iS was the profile gasket failing on the engine. The chemicals in the coolant would deteriorate the gasket until it failed. The repair for this job is extensive (cylinder head, radiator, thermo-fan, crank pulleys and the front timing chain covers are just a few components that had to be removed). The gasket would normally fail around the 50,000 miles mark and wasn't always covered under the warrenty.
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===Intake Manifold===
  
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Gasket(x1): 111 217 215 46 
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The inlet manifold is a two pieces design aimed at improving the low down torque of the engine.
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Bolt set(x1): 111 217 219 39
 
  
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Valve cover (x1): 111 217 218 76
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===Throttle Body===
  
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Valve cover (x1): 111 217 214 76
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Unlike other [[Intake#Throttle_Body|throttle bodies]] on E30 engines, the M42 throttle body has two butterfly valves, a 35mm and 54mm valve. When you are lightly pressing the accelerator pedal, only the smaller valve opens but when you further depress your pedal the larger valve also opens. This enables the M42 engine to use less petrol when the car is on journeys which do not require constant change in speed.
  
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Valve cover (x3): 111 217 214 75
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==Ancilliaries==
  
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Gasket (x1): 111 412 478 49
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===Flywheel===
  
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Gasket (x1): 111 412 478 37
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===Starter Motor===
  
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o-ring (x1): 121 417 272 20
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===Engine Mounts===
  
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seal ring (x1): 071 199 633 55
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=Torques=
  
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Gasket (x1):116 117 344 90
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When working on any engine, it is important to tighten up all bolts only to their required tightness and no further. Use the following table as a guide:
  
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Gasket (x1):116 1173 468 4
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{| class="wikitable"
 +
|-
 +
!
 +
!Nm
 +
!ft-lbs
 +
|-
 +
|Big ends - Step 1
 +
|23
 +
|17
 +
|-
 +
|Big ends - Step 2
 +
|colspan=2|+70 degrees
 +
|-
 +
|Camshaft sprocket
 +
|13-17
 +
|10-12
 +
|-
 +
|Camshaft bearing cap bolts
 +
|13-17
 +
|10-12
 +
|-
 +
|Crankshaft damper
 +
|300-320
 +
|217-231
 +
|-
 +
|Cylinder head Step 1
 +
|30-35
 +
|22-25
 +
|-
 +
|Cylinder head Step 2
 +
|colspan=2|+90-95 degrees
 +
|-
 +
|Cylinder head Step 3
 +
|colspan=2|+90-95 degrees
 +
|-
 +
|Exhaust manifold
 +
|22-24
 +
|17-18
 +
|-
 +
|Flywheel
 +
|
 +
|82-94
 +
|-
 +
|Intake manifold
 +
|13-17
 +
|10-12
 +
|-
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|Main bearings Step 1
 +
|20-25
 +
|14-18
 +
|-
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|Main bearings Step 2
 +
|colspan=2|+47-53 degree turn
 +
|-
 +
|Viscous fan coupling (LH threads)
 +
|40-50
 +
|29-36
 +
|-
 +
|Timing chain tensioner:
 +
|23-27
 +
|17-19
 +
|}
  
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o-ring (x1):115 3172 121 8
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=Servicing=
 +
''Main article: [[Basic_M42_Servicing|Basic M42 Servicing]]
  
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Gasket (x1):115 3172 117 2
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Every engine needs its fluids and filters changed regularly. And while the M42 is chain-driven, it helps to replace the chain tensioner occasionally to prevent the chain slipping and killing the engine. Learn more about [[M42_Chain_Tensioner_Replacement|changing the chain tensioner]].
  
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antifreeze (x1): 821 414 677 04
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=Common Problems=
  
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Throttle-b (x2): 135 412 474 00
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==Profile Gasket==
  
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Gasket (x1): 183 017 119 69
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The most common problem with the 318iS was the profile gasket failing on the engine. The chemicals in the coolant would deteriorate the gasket until it failed. The repair for this job is extensive (cylinder head, radiator, thermo-fan, crank pulleys and the front timing chain covers are just a few components that had to be removed). The gasket would normally fail around the 50,000 miles mark and wasn't always covered under the warranty.
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Nut (x4): 183 017 377 74
 
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Gasket set (x1): 111 417 219 19
 
  
 +
{| class="wikitable"
 +
|-
 +
!Part
 +
!Qty
 +
!Part Number
 +
|rowspan=9|
 +
!Part
 +
!Qty
 +
!Part Number
 +
|-
 +
|Gasket
 +
|1
 +
|111 217 215 46 
 +
|Gasket
 +
|1
 +
|116 117 344 90
 +
|-
 +
|Bolt set
 +
|1
 +
|111 217 219 39
 +
|Nut
 +
|4
 +
|183 017 377 74
 +
|-
 +
|Valve cover
 +
|1
 +
|111 217 218 76
 +
|Valve cover
 +
|3
 +
|111 217 214 75
 +
|-
 +
|Gasket
 +
|1
 +
|111 412 478 49
 +
|Gasket
 +
|1
 +
|115 317 211 72
 +
|-
 +
|Gasket
 +
|1
 +
|111 412 478 37
 +
|Gasket
 +
|1
 +
|116 117 346 84
 +
|-
 +
|O-ring
 +
|1
 +
|121 417 272 20
 +
|O-ring
 +
|1
 +
|115 317 212 18
 +
|-
 +
|Seal ring
 +
|1
 +
|071 199 633 55
 +
|Throttle-b
 +
|2
 +
|135 412 474 00
 +
|-
 +
|Gasket
 +
|1
 +
|183 017 119 69
 +
|Gasket set
 +
|1
 +
|111 417 219 19
 +
|-
 +
|Antifreeze
 +
|1
 +
|821 414 677 04
 +
|}
  
 
==Timing Chain Tensioner==
 
==Timing Chain Tensioner==
  
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The symptoms of a wearing tensioner is a rattling noise coming from the front of the engine which can easily be heard in the car from around 2000-3500rpm. It is a simple and relatively cheap fix, simply take the old one out and insert the new one. However, you can also re-fit an M44 tensioner. It is recommended that you change the tensioner as soon as possible when the sytpoms begin to occur; a worn tensioner will cause the timing chains to stretch resulting in in new cam chain sprockets, timing chains, guides and various gaskets and can cost in the region of £550 (including labour from a specialist).
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The symptoms of a wearing tensioner is a rattling noise coming from the front of the engine which can easily be heard in the car from around 2000-3500rpm. It is relatively easy [[M42_Chain_Tensioner_Replacement|to change the chain tensioner]]. However, you can also re-fit an M44 tensioner. It is recommended that you change the tensioner as soon as possible when the symptoms begin to occur; a worn tensioner will cause the timing chains to stretch resulting in in new cam chain sprockets, timing chains, guides and various gaskets and can cost in the region of £550 (including labour from a specialist).
  
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Timing Chain tensioner part (x1): 113 117 431 87  
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*Timing Chain tensioner part (x1): '''113 117 431 87 '''
 +
*Timing Chain tensioner washer part(x1): '''071 199 633 55 '''
  
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Timing Chain tensioner washer part(x1): 071 199 633 55
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==Adjusting Timing Chain==
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===Adjusting Timing Chain===
 
  
 
''Main article: [[Adjusting_M42_Cam_Timing|Adjusting M42 Cam Timing]]''
 
''Main article: [[Adjusting_M42_Cam_Timing|Adjusting M42 Cam Timing]]''
Line 156: Line 295:
  
 
When most people hear a ticking engine they instantly believe that the tappets are worn. This is not always the case, sometimes it can be a crack in the exhaust manifold. Normally the ticking will go away once the car has been driven for a while, so people believe tht the oil has reached operating temperature and cured the tapping problem. However, it could be a small hole in the exhaust manifold that is sealed when the manifold gets hot (ie expanding metal covering the hole up!). This is most common on cylinder one.
 
When most people hear a ticking engine they instantly believe that the tappets are worn. This is not always the case, sometimes it can be a crack in the exhaust manifold. Normally the ticking will go away once the car has been driven for a while, so people believe tht the oil has reached operating temperature and cured the tapping problem. However, it could be a small hole in the exhaust manifold that is sealed when the manifold gets hot (ie expanding metal covering the hole up!). This is most common on cylinder one.
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==Fuel smell==
 
==Fuel smell==
  
 
Some times you can smell petrol fumes on startup, which can smell alot worse if you turn on your fans. This can be a small fuel pipe just behind the inlet manifold which can perish or sometimes just needs the jubilee clip tightening. Petrol cannot always been seen (unless the engine is cold) as the petrol instantly evaporates from the heat of the engine. But you should see the leak leaking onto the fuel rail trim and down the fuel inlet and return pipes for the engine.
 
Some times you can smell petrol fumes on startup, which can smell alot worse if you turn on your fans. This can be a small fuel pipe just behind the inlet manifold which can perish or sometimes just needs the jubilee clip tightening. Petrol cannot always been seen (unless the engine is cold) as the petrol instantly evaporates from the heat of the engine. But you should see the leak leaking onto the fuel rail trim and down the fuel inlet and return pipes for the engine.
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==Lumpy idle==
 
==Lumpy idle==
Line 167: Line 304:
 
The M42 engine is prone to the air breather pipes perishing. This results in unwillingness to start on cold mornings and a lumpy uneven idle. If you open the bonnet with the engine running you may be able to hear a hissing sound. Then all you need to play is hunt the sound considering there are alot of breather pipes to the engine. If there is no hissing sound it could be the valve in the idle control valve (ICV) sticking. Simply disconnect the ICV by undoing the jubilee clips (its found between the engine and bulkhead on the passenger side and is a "T" shape) and spray some carburettor cleaner into the valve. This should stop the valve from sticking, or you could replace the ICV completly.
 
The M42 engine is prone to the air breather pipes perishing. This results in unwillingness to start on cold mornings and a lumpy uneven idle. If you open the bonnet with the engine running you may be able to hear a hissing sound. Then all you need to play is hunt the sound considering there are alot of breather pipes to the engine. If there is no hissing sound it could be the valve in the idle control valve (ICV) sticking. Simply disconnect the ICV by undoing the jubilee clips (its found between the engine and bulkhead on the passenger side and is a "T" shape) and spray some carburettor cleaner into the valve. This should stop the valve from sticking, or you could replace the ICV completly.
  
 +
==Loose Sump Bolts==
  
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=Common upgrades=
+
Due to the two-part design of M42 and [[M40]] sumps, there is a common issue of internal sump bolts working loose. Not only can this cause oil leaks, but there's the threat of oil starvation to critical parts as the sump gaskets themselves work loose and block essential oil channels. To prevent premature engine death, learn more about [[M42_Sump_Bolts|M42 sump bolts]].
  
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==Induction Kits==
+
=Common Upgrades=
−
Most people instantly buy an open cone induction kit for their car. however they are not good for the engine, as they tend to take in alot of hot air into the engine from inside the engine bay. The best air filters tend to be a performance panel filter (e.g. K +N panel filter) or a different form of enclosed air filter (e.g. BMC carbon fibre induction kit). Most people will say that the original BMW air filters are the best - and they are very good and normally better than the open cone filters.
 
  
−
==Chips==
+
==Coil On Plug==
  
−
Another upgrade is to buy a chip for the ECU. Installing a chip can induce the engine into producing up to 12 extra BHP. It is achieved by giving the car a different fuel pattern to run on (in simple terms) which increases the rev limiter, increase the low end torque and makes the car pull better over the full rev range.
+
Coil On Plug (COP) locates a set of M50 coil packs onto the spark plugs as opposed to having the standard packs on the wing and HT leads. Learn more about [[Installing_Coil_On_Plug|installing coil on plug]].
  
−
==Superchargers==
+
==Throttle Body Heater Delete==
  
−
A less common modification though is a supercharger conversion. Possibly the most famous supercharged 318iS on the E30 zone is [http://www.e30zone.net/e30zonewiki/index.php/Appletree%27s_318iS_with_Eaton_M45 Appletree's iS with Eaton m45 supercharger]
+
Some users have found that removing the throttle body heater does make a noticeable impact on the engine, based on cooler air flowing through the intake. Learn more about [[Removing_M42_Throttle_Body_Heater|removing your M42 throttle body heater]].
  
−
==Lightened Flywheels==
+
==M20 Flywheel==
  
−
Aluminium flywheels are becoming a more popular upgrade for the M42 engines. Replacing the dual mass flywheel with an aluminium version reduces the strain on the engine drastically. Instead of the stock 27 lbs the aluminium flywheel only weighs abouut 9lbs. The reduced weight means that the engine can acelerate alot faster because there is less load on the engine. However because there is less weight it does mean that between gear changes the revs drop very quickly so it is possible to stall the engine between changes. But owners who have got aluminium flywheels do say that you can get used to the drop in the revs and it soon doesn't become a problem by either quickly changing gear or bliping the throttle between gears to sustain revs. Unfortunately the standard duel mass flywheel has springs in the flywheel (and not the clutch) which reduce/stop chatter created. The aluminium flywheels do not have this so a quiet chatter can be heard and the idle can some times be lumpy.
+
Not all M42's came with dual mass fly wheels which is a common misconception. A cheaper and more road freindly alternative to an aluminium flywheel is to fit an M20 flywheel and clutch assembly.
−
Not all M42's came with dual mass fly wheels which is a common misconception. A cheaper and more road freindly alternative to an aluminium flywheel is to fit an M20 flywheel and clutch assembley.
 
  
−
==Coil On Plug==
+
==Chips==
  
−
Coil On Plug (COP) locates a set of M50 coil packs onto the spark plugs as opposed to having the standard packs on the wing and HT leads.
+
A variety of performance [[Chips]] are available to perk up the performance of otherwise-standard M42s.
  
 
==Stroker Engines==
 
==Stroker Engines==
Line 194: Line 330:
 
The M42 block is capable of much larger capacities and power than BMW made use of. If you'd like to rebuild your M42 engine into a larger capacity, learn more about [[M42_Stroker_Info|the most common stroker permutations]].  
 
The M42 block is capable of much larger capacities and power than BMW made use of. If you'd like to rebuild your M42 engine into a larger capacity, learn more about [[M42_Stroker_Info|the most common stroker permutations]].  
  
−
=Useful websites=
+
=See also=
−
 
+
*[[Engines]]
−
[http://www.esatclear.ie/~bpurcell/index.html BP's E30 318iS website]
+
*[[M10]]
−
 
+
*[[M40]]
−
[http://www.m42club.com The M42 club]
 
−
 
 
−
 
 
−
'''''**Part numbers were correct at time of typing, some may have been superceeded my a newer part. You use this information at your own risk - contact your local dealer to double check quantities/part numbers**'''''
 
−
 
 
−
=See Also=
 
−
[[Engines]]
 
−
[[M40]]
 
−
 
 
  
 +
[[Category: Technical]]
 
[[Category: E30 Engines]]
 
[[Category: E30 Engines]]
 
[[Category: M42]]
 
[[Category: M42]]

Revision as of 20:44, 6 September 2012

Characteristics

The BMW M42 is a 4-cylinder 16-valve engine, fitted to the 318is as well as early E36 models.

M42 engine

History

In E30 form it's twin cam 16v 4cyl 1796cc engine. It is an aluminium alloy engine which shares a development history with the M1, M5 and M635CSi engines.

The M42 is the last chain-driven engine fitted to the E30, and the first 16-valve unit. It featured a number of innovations that made it a far more modern engine than any other fitted to the E30, including a twin-valve throttle body, coil pack ignition and bi-concave combustion chambers. This made the 318iS both an economical and performance model, with good power and torque characteristics.

The engine also saw service in the E36, which added a serpentine belt front pulley system and a different intake manifold. It was finally superseded in that model by the M44.

The engine produces 136BHP at 6000RPM and 127 ft lbs of torque at 4600RPM

Versions

Models
Engine Displacement Power Torque Redline Year
M42B18 1.8 L (1796 cc/110 in³) 101 kW (136 hp) @ 6000 175 N·m (129 ft·lbf) @ 4500 6300 1989-96
100 kW (134 hp) @ 5500 172 N·m (127 ft·lbf) @ 4500 6300 1989-96

Components

The engine in all E30s is a three-part design, featuring a main Block with a Sump at the bottom and a Head at the top.

Sump

The M42 Sump is a two part design with an upper and lower sump. The upper part bolts directly to the block, sealed with a gasket, and the lower sump then bolts to the upper.

Leaks in this area are normally due to upper bolts coming loose, despite their torque rating. Because some of these bolts are only accessible with the lower sump removed, the two parts have to be disassembled to cure the leak. When removing the lower sump, don't be surprised to find a bolt sitting in the oil that has come out completely from the upper sump.

Oil Pump

Sump Gasket

Block

The iron block is bored to 84mm. The cylinders have a maximum ovality of: 0.01mm/0.0004" with an identical maximum taper. Compression pressures : 10-11bar (143-156psi):

Crankshaft

Crankshaft : End play: 0.0031-0.0064"

Piston Rods

Con-rods : Max. weight variance without bearing shells: 4g/14oz split equally between big and small ends

Pistons

Pistons : Clearance: 0.0004-0.0016"

Piston rings : Gap: Top & bottom compression rings = 0.0080-0.0160" ; oil ring = 0.0080-0.0180"

Firing order: 1-3-4-2

Head

The engine has hydraulic tappets which reduce the maintenance of the engine.

Cylinder head : Height = 140mm/5.512"; minimum height = 139.55mm/5.494"

Rocker Cover

The top of the rocker cover has a vapour/liquid separator which reduces oil consumption of the engine and bi-concave combustion chambers.

When removing and replacing the rocker cover, it is worth replacing the rocker cover gasket.

Cams

Being a 16V engine, the M42 head features two camshafts; an Intake and an Exhaust.

Camshaft : Duration: inlet 252 exhaust 252 Lift: inlet 10.2 exhaust 10.2

Lobe height: 1.8755-1.8803"

Valves

Valves : Seat angle: 45 degrees

Valve stem to guide clearance: 0.020"

Inlet: Solid, stem diameter 6.975mm/0.2756", head diameter 33mm/1.299"

Exhaust: Sodium filled, diameter 6.975mm/0.2756", head diameter 30.5mm/1.201"

Seat diameter: inlet = 31.6mm/1.244", exhaust = 29.1mm/1.146"

Seat width: 1.4-1.9mm/0.055-0.075"

Valve clearance : None, automatically compensated by hydraulic tappets

Rocker Arms

Head Gasket

Timing Chain

Breather Hose

To balance the pressure inside the head, a rubber hose runs from the top of the rocker cover to the throttle body.

Intake Manifold

The inlet manifold is a two pieces design aimed at improving the low down torque of the engine.

Throttle Body

Unlike other throttle bodies on E30 engines, the M42 throttle body has two butterfly valves, a 35mm and 54mm valve. When you are lightly pressing the accelerator pedal, only the smaller valve opens but when you further depress your pedal the larger valve also opens. This enables the M42 engine to use less petrol when the car is on journeys which do not require constant change in speed.

Ancilliaries

Flywheel

Starter Motor

Engine Mounts

Torques

When working on any engine, it is important to tighten up all bolts only to their required tightness and no further. Use the following table as a guide:

Nm ft-lbs
Big ends - Step 1 23 17
Big ends - Step 2 +70 degrees
Camshaft sprocket 13-17 10-12
Camshaft bearing cap bolts 13-17 10-12
Crankshaft damper 300-320 217-231
Cylinder head Step 1 30-35 22-25
Cylinder head Step 2 +90-95 degrees
Cylinder head Step 3 +90-95 degrees
Exhaust manifold 22-24 17-18
Flywheel 82-94
Intake manifold 13-17 10-12
Main bearings Step 1 20-25 14-18
Main bearings Step 2 +47-53 degree turn
Viscous fan coupling (LH threads) 40-50 29-36
Timing chain tensioner: 23-27 17-19

Servicing

Main article: Basic M42 Servicing

Every engine needs its fluids and filters changed regularly. And while the M42 is chain-driven, it helps to replace the chain tensioner occasionally to prevent the chain slipping and killing the engine. Learn more about changing the chain tensioner.

Common Problems

Profile Gasket

The most common problem with the 318iS was the profile gasket failing on the engine. The chemicals in the coolant would deteriorate the gasket until it failed. The repair for this job is extensive (cylinder head, radiator, thermo-fan, crank pulleys and the front timing chain covers are just a few components that had to be removed). The gasket would normally fail around the 50,000 miles mark and wasn't always covered under the warranty.

Part Qty Part Number Part Qty Part Number
Gasket 1 111 217 215 46 Gasket 1 116 117 344 90
Bolt set 1 111 217 219 39 Nut 4 183 017 377 74
Valve cover 1 111 217 218 76 Valve cover 3 111 217 214 75
Gasket 1 111 412 478 49 Gasket 1 115 317 211 72
Gasket 1 111 412 478 37 Gasket 1 116 117 346 84
O-ring 1 121 417 272 20 O-ring 1 115 317 212 18
Seal ring 1 071 199 633 55 Throttle-b 2 135 412 474 00
Gasket 1 183 017 119 69 Gasket set 1 111 417 219 19
Antifreeze 1 821 414 677 04

Timing Chain Tensioner

The symptoms of a wearing tensioner is a rattling noise coming from the front of the engine which can easily be heard in the car from around 2000-3500rpm. It is relatively easy to change the chain tensioner. However, you can also re-fit an M44 tensioner. It is recommended that you change the tensioner as soon as possible when the symptoms begin to occur; a worn tensioner will cause the timing chains to stretch resulting in in new cam chain sprockets, timing chains, guides and various gaskets and can cost in the region of £550 (including labour from a specialist).

  • Timing Chain tensioner part (x1): 113 117 431 87
  • Timing Chain tensioner washer part(x1): 071 199 633 55

Adjusting Timing Chain

Main article: Adjusting M42 Cam Timing

Tapping/ticking noise

When most people hear a ticking engine they instantly believe that the tappets are worn. This is not always the case, sometimes it can be a crack in the exhaust manifold. Normally the ticking will go away once the car has been driven for a while, so people believe tht the oil has reached operating temperature and cured the tapping problem. However, it could be a small hole in the exhaust manifold that is sealed when the manifold gets hot (ie expanding metal covering the hole up!). This is most common on cylinder one.

Fuel smell

Some times you can smell petrol fumes on startup, which can smell alot worse if you turn on your fans. This can be a small fuel pipe just behind the inlet manifold which can perish or sometimes just needs the jubilee clip tightening. Petrol cannot always been seen (unless the engine is cold) as the petrol instantly evaporates from the heat of the engine. But you should see the leak leaking onto the fuel rail trim and down the fuel inlet and return pipes for the engine.

Lumpy idle

The M42 engine is prone to the air breather pipes perishing. This results in unwillingness to start on cold mornings and a lumpy uneven idle. If you open the bonnet with the engine running you may be able to hear a hissing sound. Then all you need to play is hunt the sound considering there are alot of breather pipes to the engine. If there is no hissing sound it could be the valve in the idle control valve (ICV) sticking. Simply disconnect the ICV by undoing the jubilee clips (its found between the engine and bulkhead on the passenger side and is a "T" shape) and spray some carburettor cleaner into the valve. This should stop the valve from sticking, or you could replace the ICV completly.

Loose Sump Bolts

Due to the two-part design of M42 and M40 sumps, there is a common issue of internal sump bolts working loose. Not only can this cause oil leaks, but there's the threat of oil starvation to critical parts as the sump gaskets themselves work loose and block essential oil channels. To prevent premature engine death, learn more about M42 sump bolts.

Common Upgrades

Coil On Plug

Coil On Plug (COP) locates a set of M50 coil packs onto the spark plugs as opposed to having the standard packs on the wing and HT leads. Learn more about installing coil on plug.

Throttle Body Heater Delete

Some users have found that removing the throttle body heater does make a noticeable impact on the engine, based on cooler air flowing through the intake. Learn more about removing your M42 throttle body heater.

M20 Flywheel

Not all M42's came with dual mass fly wheels which is a common misconception. A cheaper and more road freindly alternative to an aluminium flywheel is to fit an M20 flywheel and clutch assembly.

Chips

A variety of performance Chips are available to perk up the performance of otherwise-standard M42s.

Stroker Engines

The M42 block is capable of much larger capacities and power than BMW made use of. If you'd like to rebuild your M42 engine into a larger capacity, learn more about the most common stroker permutations.

See also

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