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jicaino

540i Water cooled alternator dissection

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Hello! I thought I'd drop a pictures bomb on the matter.

This started as me always wanting to "upgade to the 180A" version for no reason at all.

So I struck a deal and found a bran new 180A Bosch Lucas OE new unit in a parts store that was happy to get rid of it for a 10% of what it should have costed. That alone should have raised my eyebrows but no. As it turns out, the 180A fits only certain E6x, the 745Li and the 760Li pre LCI. 

 

Front View

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side view, spatially they take up the same amount of depth

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but back view reveals the interference on the 180A unit (left one) with a plain back that will hit the bottom of the timing cover included receptacle

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cover off the 180A reveals pretty much the same internals so far

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Stators. Top one's the 150A. In the 180A you'll notice why you cannot chuck it ina  lathe and hollow out the portion that interferes. Casting has no meat because it has other features.

20210726_201852.jpg

Edited by jicaino

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180A rectifyer plate shows different numbers, anticipating different diodes

20210726_201711.thumb.jpg.63812617aa0c48ecd96acdafd2fa457f.jpg

 

this is the 150A one

20210726_201706.thumb.jpg.5de8c0b72d71e050d8ed6dd7c87251e9.jpg

 

Inducers are different too, with a protruding hub/rim that sits in the back of the stator groove in the 180A (left one)

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The overall lenght remains the same except for that detail

20210726_202115.thumb.jpg.63c0dc8fffe4c866dd044949faf9245d.jpg

 

Also, VRs are keyed differently so you cannot use your plug although I think it might work allright if plugged in (more on that later)20210726_205425.thumb.jpg.6d66394fed18b1da8cbdfbd7e35c8940.jpg

 

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At this point I tried to assemble a frankenator. 180A front plate and VR with a 150A inducer and stator. Bolted it up and off to the car I went. Installed it and sealed it, poured coolant and all, and then realized the housing key difference. Used heavy words and went back to the shop to put together a proper 150A unit back on.

 

Still, had the investment done and the water cooled alt is known for its weakness. Bearing seizure, sometimes you just start on a low battery and VR fries or rectifier fries and throws spikes at the stator which burns, the usual Lucas amenities. I wonder why they didn't put (+) to the chassis on TUs 

 

I decided to use the inductor at least. Chinese lathe obviously not up to the size of the task but spun on centre and good. Used a tailstock support

20210726_202317.thumb.jpg.519e1ccabe14aa0da1cf2fe6a9ef4cd1.jpg

 

Then I spun the inductor in reverse and with a grinder and a cutoff wheel I cutted the protruding hub leaving enough meat for a facing cut. I'll strongly advice against this method, unless you're an experienced machinist, and even so, you know you're taking chances

20210726_203300.thumb.jpg.3ae700076cbd56c07dfa3be1156e271a.jpg

 

A facing cut and compatible she looks now. this is obviously performed just on the back of the inductor, remove the "live" part (front one with the coil)

20210726_204323.thumb.jpg.564aee38bc2bfb8b1117af8e31c2777a.jpg

 

I was even able to keep the KOYO japan bearing

20210726_204750.thumb.jpg.35b4ede146e276ef444c07a0cc711569.jpg

 

Now 180 modded inductor into some cheap 150A stator from eBay (can't go wrong at 60 US$, I've used a number of those with great success on friend's cars and I even have one in my car now. I'll dig the vendor I used, they carry rectifiers, tolerance rings, voltage regulators, all you need to rebuild them.

 

 

 

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After some considerations, I might try the crossbreed thing (Will wait until christmas to shadow my neighbors efforts, just in case this turns into a spark-a-palooza)

 

A) you could buy a connector housing from a 745Li and use the pins in your car

B ) you could remove the pins from your connector, see if it fits backwards and swap the pins around

 

The diodes are bigger, the stator I don't see it having more copper or winding, will have to dissect a defunct 150A that I have and the 180A that isn't of any use to me anyways and count loops. Doing the math, if bigger diodes and a different VR are placed into a similar stator I can see at least a better scenario, being more heat generated in less time, since the DME can adjust duty cycle from 100 to 0% it could actually put the part into less of a strain to charge the electrical system of a car that was already oversupplied with 150A

 

these units are complex and delicate enough as is, so if it fails, we can all pin it on Lucas, maybe a bottle of lucas smoke can cure it after it failed.

 

Hope you enjoyed this

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Fascinating - thanks for posting.

 

I've often wondered if the V8 alternator demise isn't simply linked to the V8srunning 105degC thermostat; it's less 'water cooled' and more 'water heated'. In any other class of electronics - running wire insulation and semiconductors like diodes up towards 110degC is not a trivial issue. Silicon is only good for 150degC abs max, so the delta-T for cooling what, six diodes in pairs each running 75-90A nominal max is deeply unfunny; given there's a forward voltage drop maybe approaching 1.4v at such currents, each diode itself might well have to dissipate up to 100-140w at peak output current.

 

Likely good reason to adopt the 740d thermostat and drop to c.95degC = 20% more cooling margin from the alternators POV!

 

ETA: that 10degC drop could nearly double the life to failure of the electronics onboard - such things tend to follow Arrhenius equation.

Edited by Huff

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4 hours ago, Huff said:

Fascinating - thanks for posting.

 

I've often wondered if the V8 alternator demise isn't simply linked to the V8srunning 105degC thermostat; it's less 'water cooled' and more 'water heated'. In any other class of electronics - running wire insulation and semiconductors like diodes up towards 110degC is not a trivial issue. Silicon is only good for 150degC abs max, so the delta-T for cooling what, six diodes in pairs each running 75-90A nominal max is deeply unfunny; given there's a forward voltage drop maybe approaching 1.4v at such currents, each diode itself might well have to dissipate up to 100-140w at peak output current.

 

Likely good reason to adopt the 740d thermostat and drop to c.95degC = 20% more cooling margin from the alternators POV!

 

ETA: that 10degC drop could nearly double the life to failure of the electronics onboard - such things tend to follow Arrhenius equation.

 

I have some backup in electronics and semiconductors, not as much as you do as I gather from your very educated comments.

 

Yes, the 105°C thermostat for emissions and squeezing a couple extra MPG hurts the car in many ways. Transmissions forced to operate above 105°C, alternator "cooled" to above 105°C, all the plastics and electronics such as the DSC module subjected to residual and radiant heat and all, not to mention cooling system pressure peaking up to almost 2 bar when you pass the 102°C barrier...

 

Many water cooled alternators fail because of crappy tolerance ring in the back getting brittle and cracking, leading to the rear inductor half freezing and seizing the entide thing. Others fail from one of them diodes giving out and the voltage spikes ultimately f**king up the voltage regulator, other common failure is voltage regulator frying when you start the car with a less than ideally replenished battery, since the DME controls duty cycle on the VR, sometimes the transistor in the rather simple VR gives up and you end up with random voltage spikes that sends all data buses "on fire", and sometimes there's electro magnetic interference. There's a technical bulletin reporting it, and calling for a splice along terminal 15 (the thick red wire that goes from the alternator to the E-box along the left side e-box atop of the engine, cyls 5-8) Said diode it's a 300v 6A and it even has a P/N from BMW. Sometimes EMI will also kill that diode, or it could just bust and break on a spike. Another rarer failure happens when a bad VR "sparks" the stator and creates a short.

 

I have the 88°C thermostat and the bearings have been happy, but the long stationary times of covid lockups killed the VR because the battery decayed on long parking periods and I was too lazy or too optimistic or too who knows what to disconnect the battery or replenish it before starting the car...

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You guys need to get out more :D

 

I had my alternator repaired maybe 6/7 years ago and touch wood it’s been fine since but you never know when your E39 is gonna surprise you!

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1 hour ago, BarryM said:

You guys need to get out more :D

 

I had my alternator repaired maybe 6/7 years ago and touch wood it’s been fine since but you never know when your E39 is gonna surprise you!

 

Hey1 I have alpina cams and maps and all, do you spin it past 6k regulary? Just wondering if you beat her regularily or you occasionally indulge a left foot outburst

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14 hours ago, jicaino said:

 

Hey1 I have alpina cams and maps and all, do you spin it past 6k regulary? Just wondering if you beat her regularily or you occasionally indulge a left foot outburst

 

I run it up to 6k but not beyond when I go out for a blast, the UK roads are too busy most of the time :(

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I've still got a working alternator with a buggered bearing in a box in the garage, and a new bearing in another box... somewhere. The bearing seized so badly it was stalling and stopping the car with an automatic gearbox leading me to think it was a gearbox issue.

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