PeachParts Mercedes-Benz Forum - View Single Post - What is Inner Diameter of Air Pump Pulley? (Need Correct Drift to Remove Bearing)

EricSilver · #4 08-31-2007, 04:08 PM

This repair when well. Should anyone be interested, here is what is involved.

Tools

16mm Socket (to loosen/tighten belt tensioner)
13mm Socket (loosen/tighten pump bolts)
1.25” Socket or other Drift to push bearing out of pulley
Rubber Mallet (to hammer out bearing)
Screwdriver, Carpenters Hammer and WD40 (In case bearing has disintegrated).
Brake Parts Cleaner
Retaining Ring Pliers to remove retainer ring on pump shaft
Electrical Tape (to repair inevitable damage to pump wire insulation.

Parts
Double Row Radial Ball Bearing, Both Sides Rubber Sealed.
ID:32 mm x OD:52 mm x W: od 18 mm + id 20 mm

BearingsDirect.com
Part# 32BG05S18G-2DS
$18.99 + shipping

Note: These are the same parts sold on eBay, without the 100%+ markup. One seller uses the exact descriptive language that BearingsDirect does.

Remove Pump From Car

Remove Air Filter Housing

Remove filter cover and Filter.
Lift out the cover in front of the air filter housing, and directly behind the passenger headlight.
Remove the nut on the top rear left of the air filter housing, attached to the wiper fluid reservoir. It holds a rubber wedge that keeps the air filter housing in place.
Remove the housing by pulling up from the rear, then front. It is held in place by two plastic nipples on its bottom, which insert into two rubber “Doohickies” (Don’t know the correct term.)

Remove Fan Shroud

Pull out plastic clip on top of the circular ring part of the shroud, and tilt it against the fan blade to make room for the main shroud to be removed.
Slide off the two metal clips securing main shroud: one plainly visible on the left of the shroud, and the other on the right of the shroud, abut about an inch or two lower. Lift this shroud up and out, and then the circular ring.

Loosen Serpentine Belt

Rotate the tensioning pulley clockwise with an 16mm socket to release tension on belt. (Note: My car is late 95 E320. Your vehicle may differ.)

Remove Air Pump

Remove electrical connector to the pump. On the 95E320, it is behind the black protective cover at the front of the engine. Just trace the wire from the pump. There is a cylindrical rubber “bumper” (don’t know term) that you must slide off its post in order to move the connector from its nook. There are actually two of these. Remove the upper one.
Remove molded rubber hose from the rear of the pump. It uses a spring-type clamp that must be compressed. It twists off easily with pliers, but is a challenge to get back on unless you have the right tool for it (which I did NOT).
Remove the coolant tube that runs along the left side (facing forward) of the pump. Just detach it where it connects below the overflow coolant tank & washer fluid reservoirs.
Remove the upper Pump bolt, which is long. Then the lower bolt, which is short. If you have one of those skinny sockets, use it, as you will be working between the fan blades, and a thinner socket will be a bit easier. You will also need an adapter/extension to get at the lower bolt, if you leave the fan attached for this job.

Step Two: Replace Failed Bearing

Remove & Replace Pulley/Bearing

Remove front nut.
This was a challenge. I had do use a C-Clamp to lock the clutch in place. Once off, the clutch lifts right out.
Remove locking ring holding the pulley in place.
Slide bearing and pulley from shaft.
Use 1.25” drift to hammer old bearing out.

NOTE: If the bearing has disintegrated, and the inner race and ball bearings have fallen out (or have been removed) the outer ring will be stuck in place. Turn pulley front-side down, soak the edges of the outer ring (of the stuck bearing) with WD40, and find something else to do for a few hours.

When you return, use a screwdriver and carpenters hammer to strike, obliquely, at the outer race. Tap a few times, then rotate the pulley 30 degrees or so. If your experience was like mine, you will not complete a 360 degree rotation before the outer race is dislodged. This will be easier if you use a Dremel tool and cutting discs to grind away those six tiny retaining tabs that somewhat helped hold the original bearing in place.
Clean the pulley and place in oven at 400 degrees. Put new bearing in freezer. (Credit to MercedesShop member Brewtoo for this). After 30 minutes or so, remove pulley and bearing and slide bearing into place.

Note: I prepped the pulley surface by lightly sanding with the Dremel and sanding drum. I also sprayed a spot of WD40 on my finger and rubbed it around the periphery of the bearing when I removed it from the freezer. The bearing slid smoothly into place, after which I shock-cooled the pulley under the kitchen sink tap. Bearing was solidly in place.
Slide Pulley/bearing onto shaft.
Replace locking ring.
Replace air pump in car.