2001 V70 2.4T Brake Failure Service Urgent / Power Fluctuations / Engine Shuddering

[br0dy519]

At this point I may just go with my gut and assume it's the alternator, based on the symptoms. Now just to decide when I'm going to do it and which of the many methods I'm going to use to get the alternator out.

Forget the shortcuts, all they did for me was waste my time and upset me. Reminds me of the T-stat guide I was following where they avoided removing the PS pump. Give yourself plenty of room and time to avoid headaches like lost or stripped bolts. Prepare to remove the radiator fan (two 10mm make life WAY easier), low dipstick tube (grab a seal for it too), serp belt, and PS pump. Perhaps prepare to remove upper rad hose and drain some coolant. Maybe a good excuse to exchange 4L of coolant anyway.

It’s not a bad job at all. Biggest PITA for me was the serpentine belt, it was tight in there with my torx socket.

Good luck.

[prwood]

At this point I may just go with my gut and assume it's the alternator, based on the symptoms. Now just to decide when I'm going to do it and which of the many methods I'm going to use to get the alternator out.

Forget the shortcuts, all they did for me was waste my time and upset me. Reminds me of the T-stat guide I was following where they avoided removing the PS pump. Give yourself plenty of room and time to avoid headaches like lost or stripped bolts. Prepare to remove the radiator fan (two 10mm make life WAY easier), low dipstick tube (grab a seal for it too), serp belt, and PS pump. Perhaps prepare to remove upper rad hose and drain some coolant. Maybe a good excuse to exchange 4L of coolant anyway.

It’s not a bad job at all. Biggest PITA for me was the serpentine belt, it was tight in there with my torx socket.

Good luck.

I have replaced the alternator in this car, so I've gone through the procedure before. It's not nearly as bad as the power steering line replacement I just went through. But it's still a pain. Since I had good luck with the power steering line replacement by strictly sticking to the procedure from VIDA, I may do the same thing with the alternator. I tend to prefer a straightforward procedure that involves methodically removing parts and takes a bit longer, as opposed to a procedure with shortcuts that in theory could save time but has the potential for more frustration.

[prwood]

My father-in-law suggested an interesting idea, but I don't know if it would even work. He wondered if there was a way to disconnect the alternator's output, and start and run the car on just the battery. That way we could rule the alternator out of the equation. My questions about this are:

1. Is it even possible to disconnect the output for the alternator and still have the car function? If so, where would you do this disconnect?

2. Would the battery even be able to power the car's systems for the 20+ minutes needed to rule out the conditions under which the error occurred?

[velorider]

Assuming the ODBII info is correct, the symptoms definitely sound like a bad voltage regulator. I would and did only replace the regulator with an O.E bosch, rather then the complete alternator.

You can confirm/monitor voltage directly will driving from pin 16 and 4 at the ODBII port with a multimeter.

[abscate]

You could disconnect the heavy red wire from the alternator and tape a rubber cap over the end, then Zip tie it to secure it.

Now run the car in the daytime , lights off for your 20 minute warm up to see if that problem returns.

Over voltage would be enough for me to replace the alternator and VR , though

[prwood]

I went out and did some further testing today. This time I just had a multimeter plugged into OBD pins 16 and 4 reading DC Volts. I made the following observations of voltage during my trip:

- 11.87 volts before starting ignition
- 13.86 volts after starting ignition
- Started driving immediately, kept a stopwatch and monitored the voltage.
- Voltage slowly and steadily dropped as I drove: started at 13.86 as mentioned above, and by the 20 minute mark it had gotten down to 13.50.
- During this drive, I took a few sharp turns, but not very many. There were no issues during/after turns at this stage in the test.
- At about 22 minutes, and when the voltage was around 13.45, the BRAKE FAILURE SERVICE URGENT warning message came on, along with the BRAKE and ABS lights. This was on a straightaway, and there was no engine clunk or voltage spike yet.
- Just after this, I made a turn, and immediately after completing the turn, I got multiple engine clunks, the voltage jumped to 20 for a few seconds, then 19, 18, and back down to 13.5.
- After a minute on a straightaway, the voltage actually came back up to 13.65, but then started trending downwards again.
- I was able to make a turn right after this with no issues, but once the voltage got back down under 13.5, the next turn I made triggered another voltage spike/multiple engine clunks. I was able to repeat this several times.
- After parking and idling for a while the voltage settled in around 13.6.
- No voltage spikes or engine clunks when idling in park, even if revving engine to 4000 RPMs.

I don't quite understand why doing a turn would trigger the voltage spike/engine clunk. It happens after the turn is completed, the turn signal has shut off, and the car is driving straight again. Never during the turn itself. The issue obviously starts before the turn is made, as seen by the slowly descending voltage and the brake failure warning messages, but something happens just after the turn that triggers the voltage to spike to 20 and the transmission/engine to clunk.

[abscate]

Well, 11.87 volts is a dead battery , to start.

The turning might be flexing bad cables but you have to have a good battery Iin these cars

[prwood]

Well, 11.87 volts is a dead battery , to start.

The turning might be flexing bad cables but you have to have a good battery Iin these cars

So it's possible for the battery to have enough power to start the engine, but not enough power to safely power the vehicle's electronics?


Would there be any point in trying to charge the battery fully from an external source and repeating the tests?

Would it be worth delving into why the battery is low (bad battery, parasitic power drain, faulty alternator)? Or should I just
assume it's the alternator at this point?

Also, if it's the alternator, should I take a gamble and just replace the 5x cheaper voltage regulator, or just go straight to replacing the whole unit? My budget says to take the gamble, but I don't know if the symptoms I'm seeing point to the whole unit being bad. I've seen a number of people replacing the voltage regulator without fully removing the alternator, but I don't think I'm up for those shenanigans in this weather, so I'll likely be taking it out either way.

[br0dy519]

I’d remove the alternator and battery and bring both to a rebuilder/battery shop and have both tested. Any good rebuilder should have a pulley setup for benchtesting the alt. And they should have a good load tester for the battery.

[prwood]

Took a fairly low-risk, low-work approach today and had the battery/starter/alternator tested at Advance. Only 5 minutes away and I didn't have to disassemble anything. Obviously it's not as thorough as removing the alternator and bench-testing it on a belt drive for an extended period, but it's something.

This was their report. Note to abscate, it does seem to include a ripple voltage graph which may not be as accurate as an oscilloscope but may serve a similar purpose?

Other than the battery being low, they seemed to say that everything was fine. Of course, I had only been driving the car for 5 minutes when I had the test done, so it likely wouldn't pick up on the issues that occur when it's been running for 20 minutes.

I haven't wanted to take the alternator out just yet since the car is still drivable for shorter trips and I wanted to get some more certainty before I tied up a spot in our driveway with an undriveable car.