nlinesk8s

I'm really hoping some of the more experienced mechanics can tell me what I did, or what's wrong.

I've had my 2003 C230 sport coupe on ramps for a couple of weeks, as I removed the alternator to get at an oil leak behind it (gallery plug).

When I was removing the alternator, I did something very stupid, and that I know better, and hadn't removed the negative from the battery. I heard the zap when the alternator cable hit a ground, realized the issue, and disconnected the battery ground. Don't know if that's important here or not.

Today I put everything back together, and tried to start the car. The starter clunked, and that was it. The engine did not turn over.
So I checked the battery. Over 13v. Lights and everything seemed normal. Verified the alternator connection was tight, FWIW.
I made sure it was in neutral (standard transmission). Still only the clunk.

Here's where it gets scary:
I got out a breaker bar and large socket, and tried to turn the engine by hand. I can't turn it. Now I'm concerned.
I checked the oil level. Fine according to the sensor.
I pulled the spark plugs. They look like textbook examples.
I drained the oil and poured it into a couple of pans. Looks great, with no foreign matter or water or anything.
I pulled the oil filter. Looks like I put it in yesterday.

Either the starter has completely welded itself together, or the engine is seized. Am I missing anything?

Russell Ormerod

is there power at the back of the alternator on the thick supply cable? A short will blow the fuse in the cable. I don't understand why the engine would be solid. That's makes no sense. Did you remove the timing chain tensioner at all? Try removing the poly v belt first and see if motor turns. Failing that remove the starter and see if motor turns.

nlinesk8s

I'm going to take off the valve cover and check the chain, and put a camera in the bores next. Maybe the tensioner gave up.

nlinesk8s

Well, I solved this, and it's outside of my experience.

I decided to see whether the alternator was bound up somehow, since that's all I had messed with. I released the serpentine belt tension, and the alternator was bound up. Curiously, it would rotate backwards, but not in the direction of the engine.

Bottom line: I had it in upside down. The M271 engine has four bolts on the alternator, and you can rotate it 180 and install it. It felt a little bound up when I did the original install, and once flipped around and installed, everything was fine.

So the alternator not rotating can absolutely prevent the engine from rotating; that was a bit of a surprise.

I have to wonder if there's a gravity activated lock on the alternator, or whether putting it in backwards caused a bind. I'm thinking the former, as once removed the alternator rotated without issue, and if I'd warped something that bad, it probably wouldn't work anymore.

Looking at the manual, it does show the correct orientation, but doesn't have any notes on checking free rotation of the alternator once installed (which I should have done as a matter of course).

So, everything ended well. I feel like a bit of an idiot, but you can learn from my idiocy and not make the same mistake. The alternator bolt is to the outside, and the plug is towards the bottom.

190Efan

I'm so glad this had a happy ending.That could've turned into a very big financial issue for you as well. I'm glad you posted it in an effort to help others. It never hurts to remind yourself of the basics when undertaking such a project.

slammer111

Sorry I'm a bit lost. What do you mean the alternator was installed upside down? Would you happen to have any photos?

Donald McPherso

More likely to be serpentine belt ruited wrong if the alternator was in the wrong position to make the belt fit.

nlinesk8s

I'll try to attach a pic. If not, search for m271 alternator and you can see the four bolt pattern. Since you're working under the power steering pump, it's difficult to see. If I did this again I'd seriously consider removing the PS pump, or moving it aside.

Russell Ormerod

Like I said remove the belt first. Of course the motor will not if a pulley is seized. Probably you did distort the casing

Donald McPherso

Still can't figure it out. As long as the pulley is facing the front it will still be turning the correct way. The pulley would need to be facing inwards to go backwards. Or am I missing something?

nlinesk8s

The alternator isn't completely symmetric. Put it in flipped over and the case hits the block and warps, and the shaft won't rotate. You can install the belt but the bound up alternator stops the engine from rotating. Put it in right and there's clearance. Since you can't see anything courtesy of the PS pump, it's possible to miss that it's flipped over.