Professional software development, amateur BMW tinkering, old arcade game stuff


E31 M70 Alternator Replacement

Replacing the alternator on a V12 – this sounds a bit daunting, but is actually a fairly simple job!  The main advice I want to give though is DO NOT listen to the official service manual.  It has all sorts of steps that I found to be completely unnecessary, such as fully disconnecting the oil filter assembly (why??), the underside splash guard or installing the alternator without the pulley and then attaching the pulley in-place (surely you have hardly any room to work with that method).  Therefore I expect the official dealer ‘book time’ for this job could be fairly expensive.

I done this job working purely from the top of the car never had to do anything from underneath, except maybe push the plastic cooling tube back on when re-assembling.

Basically just strip down parts for access:

Fan (don’t need a special tool to remove it – a wedged 7mm spanner on the small nuts will prevent it turning whilst you turn the 32mm spanner on the main nut)

Radiator shroud and expansion bottle – unfortunately you will lose some coolant as I choose to fully remove it rather than just try and wedge it out the way.  I put some bubble wrap over the radiator to protect it in case I accidently struck when working on other things.

Right side MAF and air box top as pic.

Disconnect radiator top hose at radiator end – you don’t have to disconnect other end if you don’t want to, there is room just to push it out the way.

You may have to disconnect the transmission oil cooler line (right underneath radiator hose) and right side rotor just to get some wiggle room.  Can probably do it without but just gives a bit extra room to work with.

Then detension the belt at the tensioner.  At this point you can just undo the bolts on the alt and tensioner.  You can then tilt the alt forward to give you room to disconnect the two cables at the back.  Then just lift it up and out!




Re-assembly is reverse of above.  I also cleaned & filed the electrical ‘spade’ connectors as mine were a bit corroded and double checked the main cable was not shorted at any point (eg, in the metal tube it goes through to get to the jump start point).  Mine was just fine.

Replacement alt was only $112 plus $46 core from Autozone (US) – which seems pretty good value.  Lifetime warranty.  Back to a solid 13.6V with the car running :)


E38 M62 OSV / PCV – black smoke!

2000 BMW 740iL - problem – clouds of blue smoke everywhere on startup!  The internet and it’s dog will tell you this is a classic problem with the M62 V8 engine – failure of the PCV (positive crankcase ventilation) at the rear of the intake manifold.  There is a thin rubber diaphragm inside this component and if it tears the engine vacuum will draw oil through the breather pipe into the intake manifold, where of course it will be burned off and produce blue smoke.  Specialist BMW mechanics were also sure this was the problem even though my PCV looked ok…


New part was bought and fitted (extremely difficult to remove the old one as the hex bolts all stripped).  No difference!  I was so convinced this was the problem I bought a second PCV – official BMW this time instead of the Meyle part.  Still no difference.  Time to dig deeper.  You can Google elsewhere for full instructions on removing the intake manifold – but basically just unbolt stuff – you can then remove the fuel rail and wiring loom and suspend it above where it used to be - you do NOT need to disconnect the fuel line to do this.


Look at the amount of oil that had collected in the manifold!  Now to remove the right hand side valve cover and the piece that goes along side, called the upper timing cover.  This reveals the cam shaft and chains.  There was a horrendous mess of congealed oil everywhere inside the engine – it was as if the previous owner had never done an oil change :(


What we’re looking for is the oil separator valve (OSV) – as the name suggests this separates oil in vapour form coming from the crankcase back to liquid through the use of an air pressure change in the cyclone – liquid drops back to the sump and the air is pulled through to the intake manifold.  You can just about see the OSV in the right picture below – it’s buried pretty deep behind the chain but it’s the VANOS rail in particular that makes access difficult.  After cleaning up some gunk it became clear the piece of plastic connecting the top of the cyclone to the breather pipe was cracked, which effectively rendered the cyclone useless – so liquid oil as well as vapour was being pulled up through the breather pipe to the manifold – no wonder some much collected there!


At this point I admit I did not replace the OSV – to do this really requires removal of the lower timing cover – essentially the front of the engine – and that requires the oil pump to be removed along with water pump, auxiliaries, locking the cams with a special tool I didn’t have, removing the chain tensioners, etc.  You can now imagine why this would be $4000 or $5000 in labour costs at a specialist mechanic (and you probably shouldn’t trust a non-specialist with the VANOS/cam system!).  So instead I fashioned an in-place repair of the broken pipe piece – using some high temperature hosing and high temperature epoxy resin.  I wasn’t really sure this would work but when I put everything back together it worked!  I sold the car over 2 years later and it was 100% fine all that time – no reason to believe it’s not still fine.  Absolutely zero oil burning.  The horrendous oil gunk I found under the valve cover also seemed to no have no effect – the engine remained extremely smooth and powerful.






E38 Facelift CCFL angel eyes

The headlight is one of the items changed in the E38 facelift (Sep 1998 onwards).  In the pre-facelift I mounted CCFL rings on the outside of the inner clear plastic piece, but post-facelift fitting on the inside was easier and also looks much better!  Removal and disassembly of the headlight is well documented elsewhere so no need to go over it again here.  I did need to splice the power wire from the indicator/daytime running light wiring into the main light unit, as it wasn’t there on the main loom (it was on my pre-facelift cars).


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E38 bonnet / hood release cable fail

The cable to release the bonnet (hood!) came away from the mechanism on this E38 750iL.  The usual recommendation is to buy a new mechanism which will cost about £50/$80.  In this case though I disassembled the unit and managed to re-secure the cable, then re-greased everything.  It never failed again as long as I owned the car, so always worth checking for the simple fix!

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E38 CCFL Angel Eyes

This picture shows the comparison between the stock sidelights (right) and CCFL angel eyes (left) – obviously a much brighter & safer light with CCFL!  The stock lights are near useless.



E38 Bumper Removal & Trim

This E38 740i was bought with some damage to the trim on the front bumper and a bit of a scrape.  You can buy replacement trim from the dealer, but unfortunately if the car has headlight washers then the entire bumper must be removed as the washer screws into the trim on the inside.  Likewise if you need to replace the washer itself.


Removal is fairly easy – just unscrew everything on the inside of the wheel wells, then remove the two large Torx T50 bolts at the front on the bottom.  You can then gently pull the plastic connectors apart.  This can be done by one person, though two would be easier.


All better!  An all black grill, CCFL angel eyes, and clear indicators with silvered bulbs were also added in this photo.



E38 SLS hydraulic pipes

Not sure why these pics are so bad quality!  This is looking into the rear right wheel well of an E38 750iL with self levelling suspension.  The self levelling suspension works via hydraulic fluid going directly into the special shock absorbers.  A regulator for the fluid is attached to the rear anti-roll bar, so roll bar deflection leads to suspension height adjustment.  The system works at very high pressure so do not mess with it without safety equipment!  In this case..  rust had led to pinhole leaks on the pipe that attaches to the shock, so there was no pressure anyway.  Replacement is essentially just unbolting old and bolting new, but new to age and rust the old pipe can be very hard to remove.  Heat and a c shaped wrench to avoid any chance of rounding off the nuts are essential.

Once re-installed and the CHF fluid topped up the system should bleed automatically.  Remember never to use ATF as it can destroy the accumulator sphere lining!

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E38 brakes should not look like this

Old photo from around 2009 or maybe 2008 on an E38 740i…  This is how a professional garage (shop) apparently does a full brake job.  Twisted pipe which will therefore be under extra stress when the front wheels steer, and the bleed nipple cap not on.  Brake wear sensor was also missing despite them apparently ordering one specially!  Words with the manager were had and I never went back there.

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E32 Rear Pitman Arms (dogbones)

Not much to say here – just an excuse to show the condition of what I assume is the original part of this December 1988 built car in 2012!  Just unbolt old arm, 22mm socket, and attach new.



E31 Brake Bomb! (Pressure accumulator)

Problem – overall brake performance not great, ‘nothing happens’ for half a second when you want to brake hard.  Not good for emergency stops!  Car has been like this since I got it, new brake pads didn’t help much.  Brake discs are ok.

Suspected culprit – the brake booster pressure accumulator.

Accessing it is super easy – remove front left wheel, remove wheel well trim pieces (8mm bolts), and you can see it.  Before going further pump the brake pedal to get as much fluid out.

You need a 17mm ‘c’ wrench to undo the pipes – they are pretty tight and because the bomb is mounted on rubber bushes it’s hard to get good torque on them.  I took them by surprise by giving the wrench a good whack with a sledgehammer(!) – worked perfectly :)


Two 1/2″ nuts are used for the mounting, these were not tight and easy to get off.  Just pull hard on the air duct to remove it and you have easy access to the rear one.

The obligatory shot of the new piece:

Now just pull the pipes, not much fluid should leak, swap the rubber bushes over, mount the new piece, replace the trim.  Top up fluid if required (power steering reservoir).

Results – was looking good soon as I started the car – pedal was smooth and not hard like before.  Jabbing the brakes at 20mph like I did before resulting in the ABS kicking in and the car pretty much stopping on the spot (or so it felt ;).  Braking performance is now absolutely fantastic – clearly how the E31 is meant to brake!

Difficulty – very easy.
Cost – pricey – $290 is the cheapest I could find the piece versus $360 dealer list price.  It seems in the past few years the piece has got very expensive as forum posts from a few years ago talk about it being sub $100.  Because it’s pressurised nitrogen these days you can’t ship it by air either and some places won’t even mail it!