Oops! Not the turbo after all.... - PeachParts Mercedes-Benz Forum

cmac2012 · #1 11-23-2006, 05:11 AM

A while back, I stated that I thought I had ruined my turbo by running too low on oil for a while (DOHHH!!!).

For the last few months, a noise has been gradually been getting louder with a rough and grating sound that sounded a bit like having a bad exhaust manifold. I couldn't find any evidence of air pressure shooting out so that wasn't it.

A couple of weeks ago, the noise went terminal. Just a hellacious racket. Odd thing was the noise would recede entirely when I'd accelerate hard. As soon as I backed off on the pedal or went down to idle, the noise would come back very loud.

Using my stethoscope, I thought I heard the noise coming through the turbo. I'm wondering if I was just hearing the racket vibrate through the turbo housing giving the impression that the problem was in the turbo.

I'm hoping someone out there has enough experience with the 617 to recognize these symptoms.

It almost sounds like the injector noise mulitplied by 10 with some rough scraping noise thrown in.

I took the turbo off last night and used my compressor to spin the fan. Smooth as could be, also feels nice to the touch, no play at all. I wired a couple of cans to catch oil spurting out the open turbo socket and fired it up for about 10 seconds. Noise still there.

So I'm thinking injector pump or something in the valve train. Weird thing is, even when it was making the loudest racket, no noticeable loss of power.

barry123400 · #2 11-23-2006, 07:43 AM

I just reread your note and had it backwards. Noise is there until you accelerate. I would loosen each Injector line starting at number one. Might be a bearing or part that will respond to a lesser load. Number one on these engines is always a prime suspect. When you say you were low on oil I assume perhaps low enough oil pressure dropped off? Sounds like something started to go and is getting worse with time. With something like this occasionally a good full time working mechanics guess or opinion is important. As the noise is increasing time may be important here. Ten times injector noise is pretty loud come to think of it. The cam may not have liked the low or no oil either. You may want to inspect that as well. I might still inspect the chain as well for slack or other problems. The same thing applies though. It is a little hard to include every nuance in a sound description and something we leave out because we do not actually absorb it to describe it. Or it cannot be described well can be the very important indicator of the problem. Much like second guessing at this end. Hope it does not turn out to be something serious. If you ran without oil pressure for instance and could post the suspected time it will give other posters of more experience a better ideal. If you caught it right away post that as well. when you say low on oil you could just mean a couple of quarts for example so it probably was not an actual contributor to this problem. On the otherhand if you were way low and oil pressure was not there for awhile it changes the whole picture perhaps. I guess that is even more important information to post even than the present noise sounds. Is your current oil pressure as good as before the low oil episode? Does the noise change at all as the oil heats up at idle? If you think it is in the valve train a really good inspection of it is in order. That would give you a chance to checkout the timing chain tension and rails as well.

Mustang_man298 · #3 11-23-2006, 10:42 AM

If this noise began at the time you ran out of oil, its most likely some internal engine part such as a bearing, I would definitely avoid running it anymore, theres probably already been some serious damage by this point, but running it longer may result in the loss of the engine block due to a tossed rod or spun main.

I would start inspecting everything I could at this point, the vac pump is easily removed, pull it off and check it over, the lower (steel) oil pan can be very easily dropped without removing anything else, pull it off and check for any debris in the pan, use a flashlight and look at all the rods and mains for heat discoloration, mushroomed looking bearing shells, & the smell of burnt oil. Although you cant get at all of the bearings, try wiggling what you can get at to feel for excessive slop or rattling play, it is ok for them to move just a little sideways, but not ok to feel any radial slop in the direction which they run. Also pull the valve cover and check over the cam towers and lobes, look at the chain & guides with a flashlight. These are very quick cheap and easy inspections, and very worthwhile at this point.

kerry · #4 11-23-2006, 10:46 AM

As I recall, you didn't actually run it out of oil right? Just low? Have you inspected the vacuum pump?

cmac2012 · #5 11-23-2006, 02:30 PM

Good advice all. I haven't driven it since the noise went over the top. Hate to admit but I'm not sure what the oil pressure was doing at the time I noticed low oil. It was just registering on the bottom of the dipstick so I imagine it was a few quarts low.

Best case scenario is that the beginning of noise and semi-low oil is just a coincidence. Probably dreaming here, but 3 quarts low for a week or so is probably not automatic death. I mean it holds what, 10 or 12?

Oil pressure has been fine ever since this episode and I've been watching it religiously.

It really baffels me the way the noise disappears on hard acceleration. This I discovered while limping home. I would have had it towed but I suspected it wasn't deep in the block but a more exterior part. Who knows, I may be kicking myself for that one at some point.

I'll try all the checks mentioned here. Pan's coming off, and valve cover as well. I might be able to get a MB mechanic not too far from my Redwood City warehouse to do a house call and listen to the noise. I don't want to drive over as he's on the other side of the southern-most Bay bridge, about 8 miles.

SirNik84 · #6 11-23-2006, 02:37 PM

This might be a stupid post, but a few weeks back I was driving my car really hard, and it started to make a noise that made me want to kill myself every time I stepped on the accelerator. So I limped it home. It was a whirling sound, I was sure my turbo bought the farm. The next day I was looking under the hood and saw the alternator had some how come lose and the belts were dragging causing the noise...

Just thought I’d share.