For tech specs: All pre-facelift engines (roughly up to Sep 79), All post-facelift engines
Starting problems on fuel injected engines (Bosch K-Jetronic as used on 318i, 320i, 323i)
Issue observated
- car doesn't start at all but starter motor does crank the engine, checks: is there a spark at the plugs, fuel pressure, corroded fuses (roll them), battery strong enough
- car doesn't start, starter motor doesn't engage: bad battery or battery terminals, ignition lock, starter motor itself or it's solenoid/bendix
- car runs very uneven, rough: bad ignition components like distributor car and spark plug wires, or a vacuum leak (are the oil dipstick and oil fill cap in place?!)
- car fires up right away but dies after a few seconds: warm up regulator defective. Useful resource for the WUR on Google sites
- car fires up but very slowly: cold start valve (see below)
Cold Start Valve
The cold start valve (CSV) mentioned is an extra fuel injector that supplies additional fuel to make cold starts easier. With your engine I believe it is mounted in the intake manifold just above the valve cover.
The CSV is electronically operated by a thermal switch (thermo time switch or TTS, located at the top front of the engine) so the first thing you can do is to check if it is being operated at all. With cold engine, measure on the connector if its being switched on at all. If no power, the thermo time switch or wiring is under suspicion (including fuse that may be corroded, believe that's fuse no 3).
If you do have power, the injector could be stuck. Before removing it from the intake manifold make sure you have a new gasket/o-ring on hand otherwise you will have a dangerous leak after refitting. Remove the injector, leave the wiring on and be careful with the brittle fuel line. Carefully place the injector in a jar and start the engine and see if it actually is injecting fuel.
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4 cylinder
Engine code: M10 with timing chain
Used in: 315, 316, 318, 318i, 320/4, 320i
Timing chain
The timing chain is not known to have too many issues and should be able to last a lifetime. Might require some new guides and a fresh tensioner after many kms though. The engine itself is pretty strong. Known issues are:
Temperature problems
Temperature problems, overheating can be an indication of a blown head gasket, heads are pretty strong. Check for sludge in the radiator and under the oil fill cap. Usually when the head gaskets fail exhaust gases are blown into the coolant preventing the thermostat from opening, causing the interior heating to fail. Temperature should be around the center mark when warm. Another check is to remove the spark plugs. With a blown head gasket one or two spark plugs will have a whitish color opposed to the normal brown color. Remove the spark plugs when the engine is cold, refit with 23-25Nm.
Other causes of temp problems:
-worn water pump or clogged radiator (temp running up at motorway speeds due to limited flow)
-thermostat stuck in open or closed position
-temp reading on the dash is erratic (temp sender in the thermostat housing fails, BMW P/N 62 11 0 788 115)
-rad cap failing (opens up too soon, lets off pressure and coolant causing coolant consumption as well as higher temperatures due too less system pressure)
-incorrect ignition timing
-no flow in cooling system due to air pocket (see under 'bleeding' below)
After cooling system was refilled bleed the system several times by running the engine to operating temperature and squeezing the large rad hoses tight a few times. Always wear gloves and beware of heat and the radiator fan blades. Always drain, refill and bleed with the interior heating fully on.
You can check for flow to be sure everything is up and running again (also to make sure there's no air in front of the thermostat keeping it from opening). You can feel if the bottom of the radiator starts to warm up gradually as well, by hand (careful for heat and fan!) or better: using a laser thermometer.
And a useful contribution from one of our members re solving persistent temperature issues in hotter climates:
Bleeding the coolant system (getting the air out)throwback320 wrote:
I live in Southern California and my 1982 E21 (US Model 320i) was always running hot in bumper to bumper traffic, and I would stress as my temp gauge would climb over the 3/4 mark. Well, I recently swapped my old radiator for a new one (copper core all metal), ordered a fan shroud, and a new 82 deg C aux fan switch. I discovered that even though they sell the shroud stating it will work on a 1980-83 E21 you will need to swap your 400MM engine fan with the 1976-79 360MM engine fan as the 400MM will not clear the shroud. You will not need to change your water pump pulley (holes line up) to do this change and the support plate in which goes in front of the fan will also fit on the 360MM fan.
The shroud set up has made a huge difference in cooling the radiator. (Now the aux fan). I let the car sit in the garage with the motor running after a drive and the gauge started to go over the 1/2 mark at just about half way to 3/4 the aux fan kicked in as it should. The A/C does not need to be on for the aux fan to work. The aux fan will kick in when the switch (in my case 82 deg) reaches it's limit and will cool the radiator to normal temp then shut off when done.
The 4 cil versions are all filled directly at the radiator. Level should be just below rad top, any excess will be expelled through the cap (overpressure). There is no bleed screw on the 4 cil models. Perform all coolant system work including bleeding with the interior heating fully opened.
Getting rid of the air in the system: run the engine warm, squeeze the two large rad hoses tight several times, at the same time. Better use gloves and watch out for the fan blade. Keep watching the temp gauge for extreme overheating if there's no flow at all.
Other issues
Blowing blue smoke: burning oil. It might just be the valve stem seals but there are issues with piston rings as well. A compression and leak test will give you the details.
Useful info: M10 and M30 cylinder head rebuild instructions
; adjusting M10 timing
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6 cylinder
Engine code: M20 (original model designation: M60) with timing belt
Used in: 320/6, 323i
Timing belt
The timing belt is not a real weakpoint, but you have to respect its replacement interval. BMW states interval should be 80.000 kms or 6 years. Since these cars aren't run on a regular basis anymore I'd recommend 60.000 kms or 5 years. When replacing the belt which is 3-4 hrs work, ALWAYS replace the tensioner roller. If the age of the water pump is unknown, replace it as well now that you've taken things apart. Replace water pump every 100.000 kms or 6 years.
There's a very detailed topic on the belt change in the Dutch Top Tech Topics section, we need to translate that one day.
Known issues
Temperature problems, overheating can be an indication of a blown head gasket, heads are quite weak so if you keep on driving with a blown head gasket or another temperature problem you put the head itself at risk (cracking). If you suspect a blown head gasket, apart from overheating issues check for sludge in the coolant tank or under the oil fill cap. Usually when head gaskets fail exhaust gases are blown into the coolant preventing the thermostat from opening, causing the interior heating to fail. Temperature should be around the center mark when warm. Another check is to remove the spark plugs. With a blown head gasket one or two spark plugs will have a whitish color opposed to the normal brown color. Remove the spark plugs when the engine is cold, refit with 23-25Nm.
Other causes of temp problems
-worn water pump or clogged radiator (temp running up at motorway speeds due to limited flow)
-thermostat stuck in open or closed position
-temp reading on the dash is erratic (temp sender in the thermostat housing fails, BMW P/N 62 11 0 788 115)
-temp running up in traffic or at traffic light (fan viscous coupling failing-only for 6 cil models)
-coolant tank cap failing (opens up too soon, lets off pressure and coolant causing coolant consumption as well as higher temperatures due too less system pressure)
-incorrect ignition timing
-no flow in cooling system due to air pocket
After cooling system was refilled bleed the system several times on top of the thermostat housing. Always drain, refill and bleed with the interior heating fully on.
Fan clutch aka fan viscous coupling issues
The old style 13mm stud fans are horror. Hard to come by, even when ordered from the dealer at $$$$$ most of them are worn from the start due to incorrect storage, they take up more torque and don't last too long. All 'n all more than enough reasons to convert to the new style 32mm nut fan.
How to recognize: the old style has one 13mm nut with normal thread and is located towards the front: between the fan clutch and the radiator.
The new style clutch has a 32mm nut with counter thread (rotate clockwise or towards the direction of the fuse box seen from the top to undo) and is located in between the fan clutch and the water pump pulley
To undo both, put the car in gear and on handbrake, put some extra tension on the belt and press it a bit more, then try to undo with a spanner and strong pulls. Especially with the 32mm nut that's safely between clutch and water pump you can even try a few hits with a hammer.
The move to the later style is very much advised and is pretty straight forward: replace the water pump by the later type (including its updated pulley) and then you can fit the new style clutch straight away. And if you even run into fan clutch problems in the future at least then you have a clutch that is so widely used in many later models that you won't have difficulties sourcing a replacement, whether new or used and wherever you are.
I wouldn't hesitate. As said: even if you locate a replacement old style version, there is a 90% chance it's dead and you can start your search again.
Part nos M20 6 cil:
Water pump old type 1151 9 071 560, new type (originally fitted from Feb 81 on and recommended) 1151 9 071 562
Please note that the water pump pulley is model specific so if you change the water pump you need to change the pulley as well. Part no for the new version: 1151 1 271 424
Fan clutch old type 1152 1 260 459, new type 1152 1 723 918
You sure don't need to source your new fan clutch from the dealer, but please stick to known good brands for these like Febi Bilstein, Behr, Sachs, Beru.
Update 2023: the past years we've had the best experiences with Ava fan clutches.
Parts list for conversion from old style to new style fan setup:
Fan clutch (Ava BWC322 recommended)
Fan blades (outer part of the fan, PN 11 52 1 273 086, can take a used example)
Water pump pulley (P/N 11 51 1 271 424 used also ok)
Water pump P/N 11 51 9 071 561
Belt is the same for both versions (10x950mm)
Other issues
Blowing blue smoke: burning oil. Most likely to be the valve stem seals, valve guides in extreme cases. A compression and leak test is always recommended.
No problem if the engine sweats some oil, common places for oil leaks are the valve cover gasket, the valve cover breather hose, the oil pan gasket and the oil pressure sender underneath the exhaust manifold.