107 - chirping bird on deceleration

[cbdo]

My'89 560SL has a chirping from the central dash on road irregularities (bump-chirp-bump-chirp etc) but mostly during deceleration, more with braking. Before tearing into it blindly, does anyone know the "usual suspects" for this issue? Looseness in the heater blower? Windshield mount? Something buried deep in the dash requiring either dozens of hours or hundreds of $ to fix? All hypotheses welcomed---TIA

[JFawcett]

probably your blower moter fan and/or bearings.

[cbdo]

No difference whether the blower's running or not, or where the air's flowing; little heard accelerating, a bit at steady speed, more when braking, but sound like it's coming from somewhere in the center of the dash area. Ideas before we start tearing into things? Past experiences?

[Roncallo]

Its hard to diagnose from a hundreds of miles away on a computer but hears a few suggestions thta may help you isolate the problem.

1) Will it change if you put your habd on the dash while deaccelerating and going over bumps.

2) Do you have a dashboard cover. These are know to chirp when loose.

3) The blower moptor always runs even with the heat and AC off. It just runs at a very low speed.

4) Check your fan for signs of kissing the radiator or shroud.

5) Check your engine mounts.

6) Check subframe mounts front and rear and all suspension bushings

John Roncallo

[cbdo]

John, thanks for your suggestions. To answer the points--
No, I can't suppress it by steadying anything I can reach; it sounds more internal.
No, it ain't got no %$^&* dash cover--actually it's in good shape inside (mostly) and it's a Michigan car, so not sun-challenged
Fan/shroud off the hook as far as I'm concerned; the chirp is suggestive of normally-stationary parts rubbing together, not something moving that's interfering with something. HVAC blower a possibility, perhaps more as an assembly squeaking against something on body motion/stress than as a squeaky blower as such.
It needs subframe and engine mounts anyway and I think I'm gonna wait til I get that done and see what's left. Sounds like a high-pitched metal-on-metal squeak; given all the above, I'm still open to any more ideas that may come to any of you good folks out there..
Thanks again to all-

[Roncallo]

The upper control arm bushings are a steel on steel bushing encased in a rubber. If they are worn they can squeek. If you can get the problem to occur buy pushing down on the front end then it is possible to check these buy carfully placing you hand on the control arm mounts as you rock the car.

The lower control arm bushings are plain rubber mount bushings. If the bolts are loose and the inner spacer is slipping these can also squeek. More difficult to check but you can easily just tighten the bolts.

I would recomend rubber components you replace. subframe, engine mount and control arm bushing, use genuine MB parts. Yes they are alot more expensive but my experiance with aftermarket rubber is not good.

Your ball joints may have no play but may still be dry on grease. The only thing to do with these is to lift up the rubber seals and pack gease under the seals. Or of course you could replace the lower ball joints and upper control arms $$$$$.

John Roncallo

[tecqboy]

My sun visors chirped when going over bumps. I lubed the clamps with white grease and cured it. I know you said from the "dash" area, but high frequency noises are difficult for the human ear to locate if they aren't nearly constant.

[stockms]

I have the same problem and absolutely nobody can find it!!! I have spent
hundreds of dollars and hundreds of days in different shops ad still nobody can find it. It drives me crazy!!!! I have a 1992 500sl. If you can find the problem
please, please tell me what it is???

[cbdo]

Stockms, your car is a 129--totally different vehicle, and I have no clue as to what would be noisy in it. As for mine, it definitely needs front subframe bushings and engine mounts, as I'm sure they're original, and I'm going to see what's still acting up after that's done. Thanks to all for the input, as always!

[nobby]

Even if the bushings don't solve your squeaks, it will definitely improve your car.
As far as regreasing ball joints, I have had luck using a "needle tip" on my grease gun either by tucking under the boot or by forcing it through the boot and sealing the hole with black RTV.

[Pete Walls]

RE: 87 560SL: my upper ball joints seem to be OK so far but the boots are torn. It looks like the entire control arms have to be replaced to the tune of about $442 each. Is there a way that the boots can just be replaced after removing the arms, or is there a way to replace the ball joints in my control arms ?
I have some rust on the body along the seal line where the Protective cover meets the body. Anybody out there know how to remove the seal without distroying the body? I don't care about saving the seal as i am going to replace it anyway.
Thanks, Pete Walls

[Roncallo]

The upper ball joint boots are available seperatlly from MB at a cost of ~$30.00. I was advised that the upper ball joints can actually be replaced with a 124 part number but I havent tried it nor can I see how it can be done. It is definitly not an MB recomendation.

As far as your protective cover that meets the body, I'm dont understand which cover and wher on the body this is????

John Roncallo