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Old 06-03-2018, 07:19 PM
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W108 Water Pump Lubrication

I just applied a couple of drops of 90W gear oil to the lubrication hole on the top of my "67 250S.

Result: A reduction in the panoply of noises coming from the engine. I can not really describe the noise it had been making; but there was less of it. I have owned the car for nearly 4 years now, and just now noticed this lubrication point.


- Service Manual (BBB) from 1959:
See Job No. 0-9.
** A Lubrication Jobs" --
Item - Water pump, steering gear housing (standard);
Job - Check oil level, top up, if requ. (sic);
Plan E every 12,000 m - all [models]; and

** B Lubrication Chart

- Chilton's 1970 Mercedes Benz Repair & Tune-Up Guide
** Page 18:
Lubricant Recommendations chart. References SAE 90 Gear/Lube from Lists 1 & 2 for "Water Pump".

It is interesting that neither the BBB nor Chilton's goes into any appreciable discussion about the water pump beyond these cited areas. Perhaps this is the reason that there is a lot of puzzlement about whether this is a bona fide procedure.

Happy motoring!
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1967 250S - all manual with 4-spd on floor-- my Nifty 250
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Old 06-03-2018, 07:22 PM
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Should have read:...hole on top of the water pump. I did not put gear oil on top of my car.
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Old 06-03-2018, 08:45 PM
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Don't know why the M130/M180 would be any different than any other model but the water pump is lubricated/cooled by the coolant itself. Any petroleum based based lubricant would degrade the sealing surfaces of the nylon seals hence the use of a glycerin based coolant,

Any change in noise would be a temporary condition and the use of a petroleum based lubricant would probably hasten the failure of the seals.

The OLDER models (30's-'50's) were a different story. They had a separate seal behind the actual bearing/bushing and were usually equipped with a Zerk fitting.
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Old 06-03-2018, 08:53 PM
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Is the water pump on the car original to it, or has it been replaced? If it's original, it may have open bearings that the oil can get into, but if it's been replaced any time beyond the 1970s, it likely uses sealed bearings and the hole is just a vent.

More importantly, if the water pump is making enough noise to hear it over the engine, it's probably due replacement!
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Old 06-04-2018, 09:21 AM
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I always go by...."Strange noises and smells are not good in a car."

1976 280C
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Old 06-04-2018, 01:43 PM
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I think the hole you are talking about is called the 'weep hole' and its' function is to allow coolant to weep out when the seals are going bad. This way you see something dripping from your car, check it out and discover your water pump is needing replacement.

A lot of American cars from that era had the weep hole on the bottom of the pump. This made it difficult to tell just where the coolant was leaking from. Mercedes just went one step better on even this tiny item.
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Old 06-04-2018, 01:59 PM
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I just read about greasing the water pump in the 1965 edition of Chilton's manual for Mercedes Benz vehicles. I have replaced my water pump somewhat recently and assumed that the water pump design has been modernized. The Chilton's manual also contains a lengthy explanation of battery acid temperatures for maintaining the battery.

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Old 06-04-2018, 08:25 PM
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Hi all,

I gave an inaccurate citation for the factory service manual. It was not printed in 1959; rather it covers vehicles from August 1959 to December 1967.

- My water pump does not have a zerk fitting, and is not tapped for one.

- Schedule E service is recommended after every 12k mile cycle. If an expected pump life is hypotheically 100k miles, that's 8 "E" schedule lubrications of, say, 2 drops of 90w gear oil. So would 16 drops of oil substantively degrade the factory installed water pump? I don't know. Maybe the factory had to settle with the technology of the day. If the nylon elements start breaking down, even at say, 50k miles, then so be it. Remember, the factory wanted the owner to get the chassis and other mechanicals lubed every 2k miles. They expected that a factory trained mechanic would be looking at this car on a very regular basis and that there would be very few failures/surprises for the diligent owner.

- Oh, the Weep Hole. Interestingly, there is no mention of looking for water seepage from the hole as a sign of pump failure in the big manual. I've read accounts by owners of various makes of cars about their tell-tale weep holes. I would guess that this design would also show seepage as a pump failure.

I looked at my pump with a mirror, and can not find a manufacturer's name on the exterior. Is that itself telling? Did the factory pumps have part numbers or names on the exteriors?

Jeffrey - Yeah, thank goodness battery technology has advanced. By the way, love that Emerald Bullet of yours. Keep up the good work and fun!
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1967 250S - all manual with 4-spd on floor-- my Nifty 250
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