330 ci waterpump

mjkcs · 03-25-2009, 02:07 PM

is there a way to easily test the water pump in my 2001 330 coupe? I am trying to figure out an overheating issue. Please help.

Jeron · Jeron's Garage

You cant directly test it, but you can tell if it is working by the symptoms.

For instance if you get heat by the time the engine temp is warm, then the pump is working.

What problems do you have?

Jared at Pelican Parts · 03-27-2009, 07:56 AM

couple things.. but more general information than anything else.

Let the car warm up to operating temperature, then crack the bleeder screw. This should be on the the 90 degree bend piece near the top driver's side of the radiator. If coolant streams out, the pump is operating. Of course, this doesnt account for the volume of the coolant.

You can warm the car up and simply squeeze the radiator hoses. IF you feel a "surging" as you release the hose, this might guive you a good idea of how its flowing.

Is there a high pitched whine or grinding? anything that sounds like a bearing going out?

How fast does it overheat?

Manolito · 03-29-2009, 01:54 PM

Overheating is far more often caused by a thermostat that is failing to open, rather than a failed water pump. I checked one on the side of the road the other day by removing the top radiator hose and holding it up high and starting the car cold.

After about three minutes, a trickle of water started flowing which quickly grew larger as the thermostat opened. I knew that the water pump and thermostat where therefore working.

Another cause of overheating is air in the water pump. Air anywhere in the system can cause localized overheating, which can damage the engine.

Also look to make sure that your lower radiator hose is not collapsing, which would indicate an obstructed radiator or a really bad hose.

The only water pump failure that would cause it to fail to move water is if you have never changed the coolant and the impeller has rusted away. That usually takes quite a few years, so I would not expect it in an e46. The reason that we replace the coolant every three years is to refresh the corrosion inhibitors in the coolant.

mjkcs · 04-07-2009, 07:23 PM

thanks guys for all your replies. I dont get any heat at all and it doesn't take long for the car to overheat. I have tried bleeding air from the system and I don't think that's the issue. Isn't the impeller on these cars plastic and prone to failure? I initially thought it might be the thermostat but I talked to a local MB tech and he told me that if I got fluid from the bleeder screw that the thermostat is opening. I can drive the car a couple miles and be fine. The gauge will stop at dtc for a little and then race toward the red. I know these aluminum heads are touchy so I am afraid to push it too hard.

Jeron · Jeron's Garage

You will get coolant from the bleeder screw if it is overheating even if the pump and/or thermostat are broken.

If you get coolant from the bleeder before it is overheating then you have some flow.

If you are overheating quickly and have no cabin heat then it is probably the pump.

Yes many have plastic impellers but no they do not fail often. There was a bad string of plastic impellers in the early 90's that started that perpetual rumor.

Jared at Pelican Parts · 04-08-2009, 08:51 AM

Sounds like the pump at this point...

AGI · 04-10-2009, 01:13 AM

I think you can go through a temperature monitoring procedure. Before switching on the car press the left button on the instrument cluster, then turn the key one step, which normally will bring you the remaining service mileage. But this time you will see something else. On the display you will notice a '1' followed by some letters. Ignore that and press the left button 18 times, to get the number increased to 19.

You now see the display flashing On and the Off, that is tossing in between these two. Wait until the 'On' flashes and press the left button again. You are now in the instrument cluster secret function. Now, you will have to switch the car ON.

With the engine running you will have 1.0 not 1._
Keep the left button pressed now, until you get 1._ and then press it 6 times to end up in 7._, now let go of it the button to make it 7.0 which should be the engine temp. if the number shown on the display doesn't increase as the engine runs, try 7.1, or 7.2 which you should get on by the button pressed. But it may even be in the 8, so try in between 7._ and 8._ functions.

Once you're there, monitor the temp action, the M54 will normally go up to about 100-104 and then down through 93-94 during which your viscous fan will be clutched in! If you go up to the crazy temps of 110+ through to even 127 your with the electric fan kicking in, then you should have a dead or half dead waterpump, in failing MAP thermostat cases you should go up to about 110-115 and then down to 100-105 temps. Let us know how you went.