what causes the water pump to fail? - PeachParts Mercedes-Benz Forum

neanderthal · #1 10-10-2006, 10:05 PM

id like to know exactly what it is that causes the waterpump failures that seem to be the bane of these cars.

i have a 1990 300E 2.6 which is leaking water from the region just behind the water pump and adjacent to the block. it gulps about half a gallon every other day and the temperature sometimes stays in the 100s even when on the freeway. oddly enough, if i turn on the heater it still blows hot, but previously when my windshield washer heating coil thingamjig was broken and my coolant was leaking into the washer bottle, this didnt happen. no heat, i guessed coz there wasnt enough water to pump to the heating system.
anyway, i dont know if the water pump problem is a failure of the actual part or a gasket or corrosion of materials or what.
is it the gasket deteriorating over time?
materials?
part of questionable build?
or just age?

and is there anything else that i should look at before condemning the water pump.
cheers

t walgamuth · #2 10-10-2006, 10:49 PM

i think the most common mode of failure is seal failure. the pump is pretty simple. it has a housiing, bearings, an impeller and a shaft that goes to the drive pulley. the seals separate the water from the air on one side and the water from the oil in the bearings on the other side. as the shaft turns it wears the rubber on the seal til it wont seal any more.

they can also fail by the impellors wearing or corroding away, and the bearings sometimes fail, too.

but the seals i think are the most common. when they fail the water gets past them and comes out the weep hole in the housing.

tom w

wbain5280 · #3 10-10-2006, 11:41 PM

Also, too much tension on the belt will overload the bearings.

Get a good quality water pump.

DustyRusty · #4 10-11-2006, 12:16 AM

I have learned that one of the most important services on any water cooled engine is to drain and refill the coolant system with a quality anti freeze. With age, the lubrication qualities of the anti freeze are depleted, however, the properties that keep the cooling system from freezing haven't diminished much. Most people take that attitude that if it is still protecting the engine from freezing and the "color" looks good, then it is still good. I believe that changing anti freeze every two years is preventative maintenance for the engine and cooling system. I can honestly say that I can never remember replacing a water pump in any of my MB's and I usually drove them to 175 - 200K miles before retiring them. I learned early in my driving life that you can either pay for maintenance or you can pay for repairs. Usually, the repair costs far out weigh the cost of preventative maintenance. Dusty......

wbain5280 · #5 10-11-2006, 12:26 AM

Good point Dusty. I'll change the coolant in my 300SE soon.

DustyRusty · #6 10-11-2006, 01:16 AM

I don't know what makes MB's coolant better than anyone else's, but for some reason, everyone that I have ever heard discuss this, has said that you should only use the MB coolant in MB cars. The claims are that it is best for the aluminum engine block parts and prevents cavitation in diesel engines. Since disposal has been a problem for me for many years, I always left this service to the MB dealership. I did notice a few weeks ago, that there is a name brand coolant that is the same, Valvoline Zerex GO5. What I also found interesting is that my local Carquest dealer also carried the Mercedes branded coolant on his shelf. When I asked about this, he said that they can order it from the Carquest warehouse. When mixing coolant, you should use only distilled water. The reasoning for this is that distilled water has no mineral content and that the PH is 7.0 +-.

Here is a link to some information about the MB anti freeze.

http://www.peachparts.com/shopforum/Valvoline Zerex G05 Antifreeze/Coolant Phosphate Free, Long Life Hybrid Technical Bulletin (pdf).......

last question..... Do you know how to make anti freeze????