Sudden Death, 540iT

[msvphoto]

On my morning commute along scenic West Cliff Drive in Santa Cruz, CA my 540iT died pretty much without warning today. A couple modules freaked out; i.e. radio rebooted, wipers started up on a dry windshield (set to auto), trans went to failsafe, and then a few seconds later the engine stopped, but the dash was still illuminated. Car rolled to a stop and no juice at all and stuck in the middle of the road. Add to my joy is my foot is in major pain, in a surgical boot, and I was told yesterday I need to get ankle surgery. Anyway... A couple of kind souls helped push me to safety and AAA towed the car home. The AAA driver tried to jump the car and it did light up, but not enough current to pull in the starter. He insisted his jump box was like putting in a new battery, but the engineer in me politely explained to the driver that a shorted cell in the battery could pull down his jump box to the point of not enough current for the starter.

So, I am guessing alternator may have died but wouldn't there normally be some warning from a dash light? The battery could be bad, maybe a cell shorted or something. It is about 6 - 8 months old, Duralast Gold H8 (I think). Any tricks to getting the (Touring) rear hatch to open with no juice? I guess I could put a charger on the jump posts in the engine bay and unlatch that way. Should be a pretty routine troubleshoot after that, I think.

Sadly, I had planned to take it in for CA smog (renewal in June) this weekend. Now I guess once fixed I need to get some drive cycles in to achieve readiness. All the while getting ready to go under the knife soon.

[edjack]

When the alt dies, the red battery lights up.

You can measure the battery voltage under the hood, or via the ciggy lighter.

Don't know how the hatch opens. What does the owner's manual say? There must be a manual override. Have you tried the key in the hatch lock? The saloon allows a manual opening by a 90 deg CCW turn to open the boot.

[dannyzabolotny]

You can open the hatch from inside— open the tool panel on the hatch, and then there should be a tab/pull that you can pull to open the hatch, even with no power.

[msvphoto]

Thank you edjack and dannyzobolotny.

Good to know there is a manual release, I figured there must be.

No battery icon alternator light prior.

I think that sorta points to bad battery or loose or bad connection someplace. The sudden fail is strange.

I put a charger on the jump posts and was able to open the hatch that way.

Battery is charging now and ankle is on ice.

Will do some troubleshooting with help from a more able bodied friend in the morning.

[hon2bmw]

sounds like a bad battery to me. My experience with my 540iT was that it was extremely sensitive to voltage irregularities. Of course I would tell you check the voltage readings with a multimeter but if you can't get the car started, all you would be able to do is see the current voltage of the battery. I did have a bad alternator once before, but as mentioned I did get the red battery light before it went. Also, fyi, the M62TU uses a water cooled alternator, so be sure its not the battery before moving on to it, it's expensive, and you will lose coolant when you go to replace it.

It could also be a bad terminal connection, in the summers my ground cable would sometimes come loose randomly, I'm not sure if the terminal calamp stretched or what, but even though the clamp bolt was tightened all the way you could literally slip it on and off the battery with your finger. I ended buying a new cable and it solve the issue

[Qsilver7]

The Touring doesn't have an external lock cylinder on the tailgate (neither do the SAVs)...unlike the sedan's trunk...so its either the manual unlock from inside...or hook up a charger or cables to the posts in the engine bay (as the OP did).

Also, make sure that the battery cables are on tight...and that the battery hold down clamp is securing the foot of the battery (correctly)...because if not...the battery could be sliding fore and aft...which can loosen the battery cables. The battery hold down clamp is the triangular piece with the long bolt that screws down into the floor of the battery tray (not the bar that goes across the top of the battery compartment).

{battery hold down clamp securely clamped down on the battery's foot...which prevents it from moving up/down/fore/aft as you drive around town}

[geargrinder]

Yeah, because the battery term is made of just a big hunk of pure lead, they can get deformed and no longer tighten up. It's worse for the old skoolz pinch-types however that's visually obvious that the 'ears' are bent in and not clamping anymore. You can pull the cables and whack them with hammers in a vice to reform them so they tighten again with those. I know similar can happen with ours that have the more sophisticated clamper mechanism, but not sure if the same solution applies if you pull and disassemble it. If you can't get it tight, you might investigate that. I'd for sure try to fix a cable vs buying a new one, and a junkyard set of cables would be a solid #2 option.

OP you got it exact right - jumper posts to pop the trunk, as long as the cars not in a condition where you can't put power into it (i.e. its not in some state of electrical disassembly) in which case you are tunnel crawling.

[msvphoto]

Thank you all for your replies on this thread.

After around 3-4 hours on an 8amp charger the battery seems okay. Carefully resecured the terminals and tightened/checked hold downs. All seems good now. I think geargrinder nailed the diagnosis. The positive terminal may have been working its way loose. The battery looked tight, but it is even more secure now.

First check with a meter the battery the battery was 12.3v (so around 60-75% charge). After first starting the engine, idle with no throttle, voltage is a little low at the battery (~12.7 or so). Any increase in engine speed and voltage pops up to around 15 (isn't that a little too high?). Once off idle the first time the voltage at idle is closer to ~13. Never get a battery icon light (except when key on/engine off so the indicator is good). Anyway, car is back on the road and seems fine. It appears likely this episode may be my bad for not tightening the terminal clamps and/or hold downs securely enough when I replaced the battery last summer. It is a very heavy and large battery that definitely needs to be well secured.

A new alternator may be in my future as well, but hopefully not until I recover from looming ankle surgery next month.

[StephenVA]

Yep, your fluctuation of voltage at the battery (you were measuring at the battery, Yes?) is a sure sign that the regulator (built in on the BMW's) or the brushes are on their way out. More than likely both are creating wide voltage swings like charging and not charging.

There are a few quick tests that can determine alternator performance without anything other than a voltmeter.

Test 1> At idle and the meter at the battery terminals read voltage your looking for over 13V
Test 2> 1500 RPM read voltage your looking for over 13V
Test 3> 2500 RPM read voltage your looking for 13.5 - 14.7

Now Turn on all your accessories that draw amps (seat warmers, defrosters, HVAC at MAX Fan, Headlamps on HIGH, radio, etc) and run the tests again. You are looking for over 13V

Note: Before starting these tests the battery must read over 12.2V with the engine off and the key in your pocket.
Note 2,. Your alternator has the ability to adjust the voltage all the way from 12.7 to 15.8 volts depending on demand of the electrical system and battery condition.
Depending on your skills, you can "rebuild" your current unit. There are lots of DIY posted on this.
If you choose to replace your unit make sure you are buy new not rebuilt and please, match the brand you have. Most are not interchangeable Bosch/Valeo.

[msvphoto]

Thank you Stephen.

Yes, measurements at the battery. I am going measure again after driving a few days.

I thought the water cooled in 540i were all Bosch? I had to determine Bosch vs Valeo on the Audi allroad I had before the 540iT and it turned out to be Valeo.

I have done Bosch brushes/regulators many times over the years, but I think the M62TU water cooled alternator is brushless? Rebuild kits appear to be available.

I was seeing the full swing of the voltage range you mentioned, high 12s to low 15s, as an assistant reved the engine. My initial thought was poor voltage regulation.

Car is still back on the road, for now.

[geargrinder]

Great stuff from Esteban. Only thing I’d take except wif is I’ve had excellent luck with real-legit-confirmed-Bosch-brand-rebuilds (comes in Bosch box and with glossy little bosch warranty paperwork) for alternators and starters.

Note that plenny of sellers will call a "rebuilt Bosch" a “Bosch rebuilt" tho, so... Caveat yer emptor beyotches.

[blarf]

FWIW with a mostly discharged battery I was still able to get ~ 14.1V at idle, and ~14V with the fan, lights, etc. on. Don't think the alternator is brushless, just that the brushes aren't available separately from the stupidly expensive alternator. You probably could DIY the rebuild but that'll mean junky Chinese brushes.

[geargrinder]

The brushes are on the voltage regulator, which, did NOT used to be available separately IIRC, but, seems like you can get a proper Bosch VR now!? Nice.

https://www.fcpeuro.com/products/vw-...tor-1197311090

You could try pulling the VR and gently emery-ing the brush faces, and perhaps trying to blow out the receiver hole in the alt with air, and see if that helps with regulation but with the VR's being cheap now... easy enough to try a new one.

There are 2 other failure modes for these alternators, which are 1. physical seizure, and 2. internal rectifier/diode (which does not seem to be retail-available AFAIK...), and the seizure thing is not uncommon (that's why I had to get an Alt) so getting a new alternator when the original VR starts to fade is probably a good idea anyway, but nice to have the option to buy a new VR.

Somebody had posted how to self-replace the bearings, if you wanted to do that plus a bosch reg that's probably as close to a self-rebuild as you're going to get.

Just noticed that even the rebuilds now are back to being $500+, that blows. For a while the proper Bosch rebuilds had come down in price, but seems like BMW has done the 'screw those cheap poor used car owners!' price-jack and Bosch is tracking their price movements. Puts the self-service bearing replacement back in play for a worthwhile option, even if its a bit of a PITA.

[StephenVA]

GG is spot on (As always!) regarding the status of "Rebuilt Bosch" Alt & Starters as found in the market place. The companies from China discovered that those buyers seeking replacement electric parts on 10+ year old cars are driven by price not quality, so they sucked up all the volume part number with cheap as possible "Re-manufactured" white box junk. If anyone chooses to go down this path the recommendation trick is to make the seller bench test the unit to confirm that it will spin (bearing test), generate total voltage and AMP out puts BEFORE you install it and find out the voltage jumps all over the place regardless of RPM and engine load. The later will send you off chasing ghosts all over your BMW as systems stop and codes pop. The really fun ones are the units that intermittently charge, then stop, then start again as the regulator/brushes connect. You can see all of this live with a VOM/scanner or leveraging the "hidden functions" on your dash display.

IMHO, Spend the few bucks, buy new and be happy.

[msvphoto]

The brushes are on the voltage regulator, which, did NOT used to be available separately IIRC, but, seems like you can get a proper Bosch VR now!? Nice.

https://www.fcpeuro.com/products/vw-...tor-1197311090 <snip>

I have replaced more than a few over the years that look just like that in old Volvos and Audis, but unfortunately pictures of the voltage regulator for the 540i I have found look nothing like that one. In the pictures and rebuild procedures I have found there do appear to be brushes on the voltage regulator (thought I read some dis-information someplace they were brushless). FCP has a BMW voltage regulator for $510 (no thanks) and a Bosch rebuild for ~$397 which actually looks like a pretty good price. Less than Autohausaz, my other go to internet parts house.

There are "rebuild kits" but I am guessing Chinese parts.

There was a semi-recent thread in the e39 wagon forum discussing the "Power Select" alternator from Rock Auto but it is obviously a Chinese knock off. https://www.rockauto.com/en/moreinfo...358300&jsn=381

I gotta say I had real good luck in my 2001 Ford F150 4.6l with an inexpensive Chinese alternator, but it is super-easy to replace so I figured it was worth a try. The '01 allroad was no fun to replace so I bought a new Valeo for it since I didn't want to do it twice.

My hope is the main problem that started this thread as a loose positive battery terminal connection. The hold down was allowing slight movement (not an OEM battery, it is a Duralast Gold). I was able to get the hold down more secure so hopefully the terminal stays tight now (looks like it should). So far so good.

My wife is driving our son to San Jose airport Friday which is on the fringe of the range for her e-Golf so plans were for her to take her former car, the 540iT. Hopefully it will be okay. If things look sketchy next time I check voltages maybe I will suggest she take the old 4000 quattro, or just coach her on using a Chargepoint station at the airport instead.

One thought I had was to grab a Pick-N-Pull alternator and rebuild kit, but since the kits don't seem to be Bosch OE that is probably no better than just buying new Chinese and taking my chances.

Ankle surgery is scheduled for May 22 so hopefully I can get a few more months out of the alternator. Wrenching with the surgical boot sucks. Worst comes to worst I do have a friend who owns a good independent BMW shop in town if I have to find someone to do it for me because I am laid up.

Thank you all again for your help in this thread!

[StephenVA]

Good luck to one and all!