Fresh Water Pump

[TBOT422]

We recently purchased a 2007 C350, and a small leak seems to have developed in the fresh water pump. It seems to be dripping about a teaspoon of coolant in an hour of operation. The leak is so small I am having a hard time proving it is really leaking from the pump and not from one of the hose connections near it. Is there some way that I can verify the source of the leak before I spend $400 on a new pump? Is there a source for re-built pumps and are they reliable? What might have caused the leak if it is the pump? The engine only has 460 hours on it.

Thanks
TBOT422

[TBOT422]

After more investigation I still am not sure where the leak is coming from.

Last weekend, I cleaned the front of the engine and the engine pan thouroughly and ran the engine at the dock for about an hour at 2000 RPM. Not a drop of coolant anywhere to be found. As I shut the engine down, I thought I saw a single droplet dripping down the housing of the fresh water pump.

We went for a short sail the next day (we have to motor about 1/2 hour each way from the dock) to reach sailable water, and noticed coolant at the top of the pump inlet hose (probably gathering from the droplets dripping down the pump housing), and another at the bottom of the hose. Neither had accummulated enough to actually drip in the engine pan. The pump inlet hose clamps are the "wire" type and are a little rusty.

My first reaction was to just replace the hose and clamps and see if the problem went away, but I am concerned that the real leak is from the pump itself dripping down the housing on to the hose and clamps. I'm now thinking about wrapping a paper towell or cloth around the pump and holding it in place with a tie wrap to see if there is coolant coming from the pump's "weep hole" under the pulley. Is there any reason that there should ever be coolant coming from the "weep hole"? If not, then what is the purpose of the weep hole?

I'm not in a hurry to replace a $400 pump if I don't need to. Is there any reason to be concerned about this leak as long as I keep the coolant tank full? Since I've been monitoring this issue for about 10-15 hours of engine use, I haven't even added any coolant to the recovery tank, although it may be down about 1/2 inch to an inch, so the leak is very slow at this point.

Thanks
Gary (Hull #422)

[KenKrawford]

Gary, there shouldn't be any coolant in the raw water pump. This system takes in fresh (salt) water and circulates it through the raw water pump and the heat exchanger and out through the aqualift muffler. The only 2 things that could come out of the weep holes are water and oil. I think you idea to wrap the pump with a paper towel and see if there is any leakage is a good plan.
Does your engine still have the clear tubing running from the thermostat/radiator cap to the coolant recovery tank? I found a coolant leak on my engine where the tubing meets the engine. The plastic hose doesn't seem to tolerate the engine heat very well and will soon deteriorate. I replaced mine with rubber fuel hose from an auto parts store. Just a thought.

[TBOT422]

Ken,

Thanks. I am not referring to the raw water pump. I am referring to the fresh water pump (the one closer to the top of the engine). I believe there is a weep hole under the pulley.

Yes, it still has the clear tubing, and I have looked at it, but don't see any signs of leakage as yet, but it certainly is suspect, and it lays directly on a hose clamp near the thermostat.

Gary (Hull#422)

[william vanwagoner]

I also had a coolant leak and very much doubt it is your pump. In my case the clear plastic tubing at the thermostat housing leaked. Additionally, there is a very expensive hose custom shaped that runs from the heat exchanger to the elbow shaped hose to the water pump which had a pinhole leak due to rubbing against the engine on the port side. Coolant can wick a long way along a hose prior to dripping off. I would look long and hard at your hoses and connections before tearing in to your pump

[TBOT422]

I would look long and hard at your hoses and connections before tearing in to your pump

Amen to that, William. I'm not excited about $400 for a new fresh water pump if I don't need it. Several people have stated that they doubt it is the pump. I agree that coolant can wick a long way before dripping, but it doesn't usually wick upward. The short molded hose at the fresh water pump inlet and it's clamps don't look the best, and I thought about just replacing it, but some of the coolant traces and droplets I've seen are above that hose on the pump housing itself. I'm going to spend more time trying to locate the culprit and keep an eye on the coolant level before spending $400 on a new pump.

Thanks
Gary (#422)

[william vanwagoner]

My bet is the clear plastic hose at the point it connects to the thermostat. It may look fine but still may be leaking. Mine looked fine but when I went to remove it, it fell apart. I was able to buy some heater hose from A NAPA auto parts store resulting in a much more robust setup.