drbs

I have a 2006 530xi wagon that has been garaged kept. The starting became slow and labored, so I took it to auto parts store and they tested the battery. The testing results were that the battery was good but very low on charge, the alternator diode was shorted with no load voltage of 14.52, loaded voltage of 14.49 and ripple voltage of 346 mV. The starter could not be checked with a low battery. Went home fully charged the battery and the car started better, but not perfect. Checked the alternator by pulling the negative battery terminal disconnecting the power cable (one bolt) then checking the diode. The diode checked out, so I put the bolt to the alternator back on and replaced the negative battery terminal. Now the car will not start. when I press start I hear a light click and a hum for a moment, which then stops. I replaced the battery (it was 8 years old), checked the engine ground and disconnected the IBS and I still just get the hum on start. Any ideas? Could the starter have coincidentally gone bad?

twh

Which engine ground did you check?

habbyguy

Did you replace the bad alternator (a third of a volt of ripple is FAR too much)?

What is your battery voltage when you're trying to start the car now?

How do you check "the diode"? (There are many of them in an alternator).

Why did you replace the negative battery terminal? Did the non-start issue start when you did that, or did you do all the things mentioned in your post all at once, and then try to start the car?

At any rate, at a bare minimum, I'd recommend checking the battery voltage (under "load" of trying to start the car, ideally), and the voltage drop from the battery negative terminal to the engine block (also "under load"). If the latter is more than a small fraction of a volt, you have a bad ground strap (body to engine block, a common failure).

If you've got a solid 12 volts at the battery (and at the "jump block" under the hood), and the ground strap is good, AND you're hearing the starter turn, but not engage (at least that's what your description sounds like), I'd say your starter is bad. But don't neglect doing the first (easy) steps before swapping a starter in an N52 car - that starter is a bear to get to.

drbs

Thanks for the responses.

I checked the grounding strap on passenger side near the radiator fluid tank. I also grounded the engine with jumper cables.

I have not replaced the alternator yet. I used the diode check I found on YouTube, which I think is the diode associated with the positive terminal on the alternator (sorry if using wrong terminology) and prevents the flow of electricity from the battery to the alternator. My thought was that this was potentially causing a drain on the battery, but was not the case.

I did not replace the negative battery terminal, I meant to say, I put it back onto the battery.

The voltage for both the old and new battery were at 12.3 to 12.5 volts. Since the old battery started the car 15 minutes before all of this, I do not think it is a battery issue. I will get a helper and check the battery under load just to be sure.

I do not think I am hearing the starter turn. I think the click is the solenoid engaging, but the starter does not turn (as best as I can tell), I think the hum is from the fuel pump.

It sounds like the alternator definitely needs to be replaced, so I will do that. Could the bad alternator cause the car to not start with a good battery? Also, are the rebuild alternators from e.g. autozone any good, or should I get the OEM. If the OEM needs to be mailed ordered. Thanks again.

seanjordan20

Bosch or Valeo or Rockauto would be the cheapest. They are the OEM brands. I personally wouldn't go with the box store.

drbs

The battery voltage under starting load was 12.2 volts, so that's OK. I just ordered the Valeo alternator and some bolts from Rockauto and will let you know if that fixes it. Thanks all.

twh

I will say that my wife's old N52 X5 starter got weak and a new Bosch fixed that up. And, on my 2006 530xi, I replaced the starter when I had the intake manifold off for other work and the new one was noticeably stronger, although it wasn't concerning when I did it. Could just be the starter. Removing and reinstalling the manifold is a PITA. New Bosch at Rockauto is $145. Don't forget you'll need new aluminum bolts and some Torx tools. The rear bolt is long and difficult to change. Use a torque wrench.

You should read the codes just in case something else is hanging around.

habbyguy

I too swapped my starter when I was doing "the big service" and had the intake manifold off. Just FYI - if your car has well over 100,000 miles and has never had the oil separator and hoses changed, you'll want to have them on hand to swap out (because chances are the hoses will break, and the oil separator is probably well past its expiration date). Also check that rear DISA valve. I swapped it as well, since the front one broke (scaring me to death at first, thinking something in the drivetrain had cut loose).

Anyway, once the intake manifold is out of the way, replacing the starter is easy - except for that "one bolt". I did a short video (who woulda guessed?) on that.

drbs

Thanks twh and habby, I did check the codes and nothing unusual came up. I am hopeful that the starter is OK and it's the alternator or something simple preventing it from starting. If I do change the starter then I would want to use that as an opportunity to change anything that is likely to fail. I added the oil separator and hose and rear DISA valve to the list. Anything else I should think about changing? By the way, the car only has 90,000 miles which are mostly highway. It was my parent's and was well maintained and has sentimental value. It has reached the point that every year somethings needs to be replaced and recently changed the radiator, hoses and oil filter housing gaskets.

habbyguy

I also did the oil filter / cooler housing seals, and don't forget to take a close look at the vacuum line from the vacuum pump back to the brake booster (it can get hard and brittle).

One thing that might save you some time is that (AFAICT) the little connectors that go off several directions to the heated oil separator hose heaters seem to all be identical, and think they can be connected to any "port" on the connector block. But no matter what, mark hoses and connectors as to where they go / connect so you don't end up with something disconnected or plugged into the wrong place.

This gives you an idea of what things will look like right before you start reassembling things...