Hello all, I just signed up to get some guidance on diagnosing my 2004 r53 Cooper S. It has 129,000 miles and is pretty much stock other than 16" wheels.

While I was driving a few years ago (perhaps 2-3) everything on the dashboard lit up and then went blank. And the car died. I pulled over, sat a minute or two, and then it did start up and got me home five or ten miles. I had few options other than towing hundreds of miles to a dealer or pay thousands for local people to fix (no one really wanted to), so I drove another car until now. I figured it was the alternator because I could charge the battery with a charger and then the mini operated normally for a short, unreliable amount of time. It has been a while, but I also think I used a multimeter to confirm the voltage was wrong. But I just lost track of my poor mini as life went by.

Now to today, I recently noticed the parts needed are in my price range and seem doable. From my reading, I gather there are many possible reasons for the "dead car" that I experienced. A tensioner shock could be faulty, the crank pulley may be failing, the alternator could actually be bad like I originally thought, and perhaps other issues.

So I tried jumping it the other day with the dead battery in place and it wouldn't start. No typical starter noises. So, this is either a starter issue or a cable problem? Or is it possible a new battery I'm getting tomorrow would somehow work differently than when I try to jump? I tried jumping with two different cars just in case.

It sounds like I'll need:
-battery (any benefit at all to get an agm version over standard lead acid?, seems agm is perhaps heavier)
-starter (there seem to be two versions for the r53 so I need to get the correct one)
-alternator (several readers indicated cheap rebuilt alternators fail much quicker, not sure about "new" non-denso vs $$$ denso)

While I'm down there, replace with the correct sized belt and 15% pulley, and check the crank pulley and tensioner shock.

Does any of this sound suspect? I think I'd also need to check to make sure the cabling hasn't been damaged.

Thanks. I've done a lot of reading the last few days, and watched some videos, but its always easier to ask those with experience.

 

 

I had this happen to me a couple weeks ago (xmas tree dash, car died on the road, low voltage, jump did not work). Turns out the alternator was indeed failed, and it failed as a dead short. So no jump or charger would ever work as it just dumped heat into the alternator. You can take a good quality multimeter and measure across the jump terminals for a minute after disconnecting the battery - you should not see a continuous short of a few ohms (normally you'll see a few ohms initially but it'll rise to a large number as the capacitance of the systems saturates). If you want to double confirm, you can try to charge the battery in and out of the car. Mine would not charge on the car but would when taken out

 

I would check to see if all your ground straps are cleaned and in place.

 

Thanks to all the replies. Ground straps, dead short, etc, this is the stuff I've probably read at some point and couldn't verbalize properly.

Hope to get a few things done tonight. I did just purchase a new battery because I'm almost 100% sure I couldn't save it and at least I can cross one thing off my list. At the very least I'd feel better with a new battery far from home.

Thanks again.

 

Interesting, my alternator just died a few weeks ago. This is my method for testing if it is the battery or alternator:

1. Put a multi-meter on the battery terminals
2. Have a partner rev the engine

You should see 14.5 V or more across the battery terminals as the engine gets revved, if the alternator is functional, regardless of the state of the battery. I was seeing 9.5V or so, which meant my alternator was toast.

If you do see 14.5V+ on the battery terminals, then you can be pretty sure that that battery needs replacement, as the alternator is delivering enough voltage to charge it up.