606 groaning under load
 

My 99 606 has been making a groaning noise when you turn the headlights on at idle, it gets louder when you turn the fogs on or turn the wheel. When you shut the lights off the groaning noise goes away. I have to assume the alternator pulley or bearings are going bad but I wanted to see if someone else has been down this road.

I have had no charging issues and the car runs fine besides this annoying noise.

Motor mounts replace 6 months ago, car has 189k

Check all pulleys, P/S fluid and filter.

Power steering fluid is on my list for replacing along with the filter that I have read is very hard to see.

My problem appears to be coming from the alternator pulley or alternator itself as I placed my stethoscope on top of alternator and I can hear the droning groan louder.

Have any coolant loss issues lately? Often the water pump drips onto the alt, prematurely waxing it.

no coolant leaking, but the water pump is going to get replaced this summer along with the coolant, T-stat and hoses as maintenance.

I think I am going to replace the PS fluid to see if it helps. I noticed a power steering filter listed as a part but I am not sure how to change that.

As for the fluid I will suck out what I can multiple times while turning the wheel lock to lock several times.

I had a similar problem and it caused a failure of the belt tensioner. Turned out to be the alternator - so the sooner you address the issue with the alternator the cheaper.


Jim

Jim-

Is there a way to rebuild it or did you just buy a new one?

By the time I reacted I had to buy a new one - actually traded the old one for core value - and had to put a new belt tensioner in at the same time.

Jim

After further inspection... I had a friend come over and help with the groan inspection, one to man the headlight switch while I use the scope. I noticed the pulley on the water pump to be wobbling like its bent slightly. It is enough to notice but its not making the belt jump. I placed the scope on the water pump housing and the groan seems to be coming from the water pump as its louder then when I place it on the alternator. Or its just making it sound like its the water pump pulley and its really the alternator-either way I need to do this maintenance.

I think my game plan is to do my coolant maintenance now instead of waiting until summer like I was planning. Replace water pump, pulley, t-stat, coolant and both hoses. If the noise is still there then move on to the alternator.

This makes sense since there's more side load on the WP pulley as the alternator load increases.

just to update in case someone else is searching this issue.

Replaced the water pump, coolant flush, t-stat and housing and both hoses. Water pump bearings were shot, you could hear them turning it by hand. What I did not order was the belt tensioner pulley and as I discovered it was making rattling noise when I removed it so I replaced it as well as the fan clutch as it was leaking fluid and original.

All back together and the noise is still present, although quieter. It is the
alternator pulley as well so I am sure the bearings are bad. I am ordering a new alternator now, 115amp version. I guess a 190,000 miles is enough to ask of a alternator. it may have been the alternator bearings dragging that caused the water pump and belt tensioner to go bad as well, who knows, but at least I have it all sorted out now.

Tensioner and volt reg
 

The belt tensioner on my 95 was totally shot. Search this forum for my recent post on this. Dont neglect this. Easy to evaluate while you're in there. Check status of the tensioner arm and make sure the pivot pin isn't damaged.

My 95 groaned too. I didn't positively Identify the issue but it hasn't since I replaced the thoroughly worn down voltage regulator - another easy fix.

Tensioner is already replaced, and it was bad. If your saying the groaning stopped after a regulator replacement maybe I should cancel my order for the alternator and just get the regulator

@ 190 K
 

The Alternator "Slip Rings" (The VR's brushes contact them for transmission)
along with the Bearings of the alternator itself probably need replacing.

These Two remans should tell you all you need for Bosch Alternator rebuilding:

Oichan's Corrado Alternator Rebuild.

Alternator Bearing Replacement in a W140 Mercedes