charge indicator light on, steering becomes hard - PeachParts Mercedes-Benz Forum

TJR300SD · #1 09-08-2007, 03:23 PM

Something odd happened to my '83 300SD today.

As I was driving down the road my charge indicator light came on; at the same time it became very hard to steer (steering pump failed?). (There was also an odd noise that I heard a second or two before this happened, but I can't quite describe it. Thud? Whop? Fhup?) So I pulled over to the side and turned off the car and had it towed back home.

When I got it back home, I made a brief visual inspection under the hood. Nothing unusual visible, so whatever it is it's internal somewhere. I turned it back on. Immediately after the engine turned on there was a brief (one second) but strong shudder from the under the hood. However, afterwards it ran fine--no indicator lights, steering was fine, engine sounded fine. I drove it slowly around the block to test. It ran as it usually does.

Now the German car shops around here are closed on the weekends

. So I have some time before I take it to the shop to be inspected on Monday. I'm not so confident about driving it that far yet, though.

What do you guys think?

#2 09-08-2007, 03:29 PM

The only common thing is the belts. However, the alternator belts are separate from the power steering belt, and belts don't fix themselves. Take a look at the belts and the crank pulley (the main pulley with four belts) and see if anything is broken or lose. Make sure the pulley isn't lose on the front of the engine.

toomany MBZ · #3 09-08-2007, 05:36 PM

Quote:

Originally Posted by Craig

The only common thing is the belts. However, the alternator belts are separate from the power steering belt, and belts don't fix themselves. Take a look at the belts and the crank pulley (the main pulley with four belts) and see if anything is broken or lose. Make sure the pulley isn't lose on the front of the engine.

Agreed, a head scratcher. Did the rpm drop at the same time?

#4 09-08-2007, 05:53 PM

Quote:

Originally Posted by toomany MBZ

Agreed, a head scratcher. Did the rpm drop at the same time?

I'm a little concerned that his harmonic balancer may be loose, and it allowed all the belts to slip at the same time. I can't think of another explanation.

bgkast · #5 09-08-2007, 06:16 PM

Quote:

Originally Posted by Craig

I'm a little concerned that his harmonic balancer may be loose, and it allowed all the belts to slip at the same time. I can't think of another explanation.

That would be my guess as well.

TJR300SD · #6 09-08-2007, 06:40 PM

Quote:

Originally Posted by bgkast

That would be my guess as well.

Harmonic balancer? Is that the same thing as the "vibration damper" I see on an exploded diagram of the crankshaft? That thing right behind the crank pulley?

#7 09-08-2007, 07:11 PM

Quote:

Originally Posted by TJR300SD

Harmonic balancer? Is that the same thing as the "vibration damper" I see on an exploded diagram of the crankshaft? That thing right behind the crank pulley?

That's it, if it was to come loose it might allow the main pulley to move around and let all the belts slip. I would try to move it and see if it's moving around with the engine running.

pawoSD · #8 09-08-2007, 08:35 PM

I thought the same thing, loose crank pulley, you really should check that right away before driving it any further.

TJR300SD · #9 09-09-2007, 02:09 PM

The problem appears to be loose belts. I "tested" the tension by pressing on the belts on the power steering and the alternator, both of which gave in easily to my forefinger. I didn't have a gauge or any measuring device but the deflection appeared to be more than 1/2 inch--under a relatively soft pressure from my finger. On the other hand, the compressor's belt was tight, deflecting only by about 1/2 inch under a stronger thumb pressure (my forefinger can't push it as much).

I adjusted the tension on the power steering belt to match the compressor's. But when I tried to adjust the alternator's, that nut on the adjusting bolt just wouldn't budge!

With the adjusting bolt tight, I could not turn that adjusting nut to tighten the belt.

The crank pulley and the other pulleys are not loose from what I can tell. I tried moving them and applied leverage but I couldn't. I also observed their motion with the car running, and I saw no wobbling or any loose indication. However, as I suspected the belts on the alternator moved (or vibrated) side to side as the pulley turned. The belts on the power steering and compressor just moved smoothly in the direction of the pulley's pull.

Is there a more accurate way to measure belt tension/deflection without having to buy a fancy gauge? Or is the apply-strong-pressure-with-thumb technique adequate?

toomany MBZ · #10 09-09-2007, 02:46 PM

Your method of testing the belts are fine, the alt belts can be tricky as you need to loosen, IIRC, there are three bolts, one of which is the adjusting bolt itself. The way I did this was from under the car the 17mm, I think, bolt (no nut on this one, as it threads into the bracket) near bottom outside of alt. Then in front near engine there is another 17mm bolt with nut, I put an open end wrench on the back side, and a socket on the front end, you need to move the fan around a bit, this is the bolt I bent my ratchet on, loosen. Then the nut on the back end of the "L" adjuster bolt, this allows you to use a 13mm socket on the long nut lookin' thing. The only way I know of to check crank pulley, would be to remove all belts, or tighten down the bolts holding it on, try to anyway, if they don't budge, should be OK. Hope this helps.

pawoSD · #11 09-09-2007, 02:57 PM

Make sure to loosen the mounting bolts on the alternator before trying to use the adjuster!

If you don't you'll just break the adjustment bolt and it won't budge.

Cervan · #12 09-09-2007, 03:12 PM

your engine could have stalled...

TJR300SD · #13 09-09-2007, 04:29 PM

Quote:

Originally Posted by Cervan

your engine could have stalled...

You mean, when steering got hard and the charge indicator light came on?

No, unless a stalled engine continues to run

. I was able to maintain speed and even accelerate until I found a spot to pull over. Then I turned the key to shut off the engine, which of course went from that rackety diesel sound to silence.

TJR300SD · #14 09-09-2007, 06:19 PM

Quote:

Originally Posted by pawoSD

Make sure to loosen the mounting bolts on the alternator before trying to use the adjuster!

If you don't you'll just break the adjustment bolt and it won't budge.

I know. It's just practically impossible to get those bolt nuts loose with brute force. I haven't touched the adjuster nut yet. Now for more drastic measures...Any suggestions? Those nuts are driving me nuts!

Palangi · #15 09-09-2007, 07:05 PM

One of those "nuts" is welded to the alternator bracket. Offhand, I don't remember if it is on the front side or back side of the bracket, but I do remember that one of 'em ain't going anywhere.