My '90 300D w124 heater/AC fan is chirping as it runs. It's not constant. It sounds like a bearing is running dry. Any guidance would be appreciated. Thanks.

The motor that is part of the blower assembly has bushings (not bearings) that dry out over the years and can give the symptoms you describe. It is a hassle but not a terribly difficult job to pull the trim, the windshield wiper, and then the blower assembly. Once you have the blower out, you can clean and lubricate the bushings. It might also be possible to squirt some oil in without pulling the blower but I've never tried that and do not recommend it. Others may have other opinions.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Jeremy,

Would I replace the bushing or simply lubricate it? Can I replace it or is the cleaning/lubricating you describe sufficient? Have you done this before? Would the FSM be useful for this task?

Is the difference between a bushing and a bearing the presence of a ball or roller?

Thank you.

Stuart

Mine was chirping away pretty much constantly and driving me nuts last year, pretty sure it's because small particles get into there by getting past the small plastic grille in front of the wiper. I made a 'filter' by cutting up an old metal speaker grille and gluing it to the bottom of the plastic one.

Then I lubed the blower it in situ: I greased the ends of the 'hamster wheel' spindle, and sprayed plenty of silicone lube into the centre part. Has been silent (touch wood) since.

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1993 320TE M104
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past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
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"music and women I cannot but give way to, whatever my business" -Pepys

Thanks. Do I access the motor from under the dash on the passenger side?

under the front windshield wiper assembly.

OK. I'll pop the hood and look. Thanks.

PS - What's the difference between a bushing and a bearing?

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Follow-up

I've looked under my hood. On the driver side is the brake booster. On the passenger-side, behind the battery is a plastic shell. Is that where I can access the blower without removing it or do I need to pull the windshield wiper assembly?

Thanks.

This isn't a fun job. The wiper doesn't need to come out, nor the rubber trim. I'm trying to remember it all so forgive me if I forget something, it'll become obvious once you start taking things apart what needs to come off. Mine is a '94 diesel but I suspect they're pretty much the same.
Raise the hood to fully-open (service) position. You need to loosen at each side, but don't remove completely, the bottom windscreen rubber trim, then loosen the plastic scuttles at the base of the screen, there's screws you'll see so they can come loose. Get them loose and out the way. You'll see where they overlap. Remove the plastic cover if it's there for your ovp etc relays, get that out the way. Remove the rubber weatherstrip that goes over the rear bulkhead (in front of the battery/brake booster). Unclip the centre plastic bulkhead part on each side and take it off. You'll see two big plastic screws at the back of the engine bay that screw into the heat-proof material, undo those and behind the heat-proofing material there should be 2 more small screws, they're quite well hidden. Once all those are out, you should be able to wrestle the whole fresh-air vent assembly out. You may need to park the wiper straight up to help get it under the rubber trim. It'll seem like it doesn't want to come out but it will, and nothing should break! Once that's out you'll finally see the blower motor and fan cage.
What a pain in the arse. Luckily it (seems) to go back together a lot quicker than it comes apart...

p.s., when you put it back together, make sure the tabs on the heat-proofing material lock into the bottom of the plastic bulkhead piece.

__________________
1993 320TE M104
---------------------------------------------------
past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
----------------------------------------------
"music and women I cannot but give way to, whatever my business" -Pepys

Thanks. Now that I know what is before me I will plan accordingly.

A bushing generally uses a soft material such as bronze or plastic, held in some kind of supporting framework, with a hardened steel shaft spinning in a hole bored in the soft material. Some are designed to run dry, others are lubricated. Some bushings are sintered, that is, the bushing material is treated to create pockets or holes that will hold oil. Bushings are less expensive than bearings and generally are used for light-duty equipment where the parts do not spin at high speed or under heavy loads.

The problem in your specific case is that because diesel engines last so long, the cars tend to be operated for many years past the normal service life of the bushings in things like the climate control blower. Very roughly speaking, many of the bushing-using parts in a W124 are designed for the life of a gasoline engine, e.g., 100,000 - 200,000 miles. This means you end up replacing things in a diesel while a gasser would long ago have gone to the wrecker.

A bearing can be a ball bearing or a roller bearing or a "plain" bearing like crankshafts, rod journals, camshafts, or turbochargers use. In a plain bearing, pressurized oil is applied to the bearing area such that the metal parts never touch. All bearing like clean oil, especially plain bearings.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Thanks.

I thought it was something like that but couldn't see the distinction between crankshaft bearings and bronze bushings. Your comment on active lubrication brought it into better focus.