Water pump failure rate on 85 300D?
 

I just can't identify where the coolant drip from the passenger side front of my 85 300D engine is coming.

There is an outlet assembly near the front of the cylinder head where two big hoses connect; its held on by two bolts. I thought it was coming from there and I replaced and carefully sealed the gasket. I have also replaced the hoses.

I think there is a water plug slightly below that location.

I see the coolant on the front top flange above the oil pan. Because of the fan running, its hard to find the source of the coolant. I'm checking everything coolant associated in that area.

Could it be the Water Pump? The engine has 250,000 miles on it.I'm starting to think thats it. Does anyone know the water pump failure rate of the 300D engine?

water pump
 

I have a 240D, 1983 Mercedees.
At about 250K miles, I also had an anifreeze drip coming from the water pump and eventually realize, it was coming out of a drip hole that was on the bottom side of the pump. This hole is made so that when the seal on the water pump shaft (that spins where the blade is on the inside to rotate the antifreeze) it drips out of the drip hole.

Get prices on the water pump. I think Mercedees wanted like $300 and got mine at Karr parts for like $75.

Replacement is very easy. Just loosen up fan belt. Take the bolts out that hold the fan on. Pull back and forth hard to get it offf. Don't forget to buy a water pump gasket if it calls for it.

Hope it helps.

MB price is rather low on the 300D water pump IF the core is a genuine MB water pump. Look for a little MB star on the old pump casting. Exchange price should be about $ 60 to $ 75 or so.

Carrameow,

The pump assembly should last at least 70,000 miles and often quite a bit more depending on the condition of the coolant. I have replace the water pump on my 1982 240D twice in 279,000 miles (meaning the first, original pump and the second one I put in lasted about 140,000 miles each). The job is relatively straight forward. I did it in a parking lot once. You take the fan belt off as noted above, remove the fan, and the clutch assembly. Then the access in the area is sufficient to take the pump off without taking the radiator out. The pump should come with a gasket. I used a sealant with it just because the sealing surfaces looked a little worse for the wear.

So, I hope this helps, and good luck! Jim

Hold on! Before you go replacing the water pump, you need to go out and check the fat bypass hose that connects the water pump with the thermostate housing. If it is damp or has dried coolant residue on the rubber, try tightening down the clamps. I had a similar situation, where there was coolant leaking on the passenger side (off the alternator bracket in fact), and it turned out that both upper and lower clamps had worked themselves very loose.

Good luck,

Greg
'84 300D

If you replace the water pump, you definitly should replace the bypass hose which Greg described. It is not accessable with the water pump in place.