After stopping the engine there is a noise that hums, it sounds like a pump that continues to run for about 3 to 5 minutes.

I am just wondering what this is.

Thanks

Now I can hear a notably loud humming that accompanies this noise, I can even hear it when driving, and it continues for a few minutes after stopping the car.

Is my water pump going bad?

I have been replacing a lot of aux waterpumps lately for this exact problem. very very noisy. It is mounted just next to the
battery shield in the engine bay. Very easy to replace.
make sure the rubber mounts are in good shape too.
DR.D

How can I be sure that this is what needs to be replaced?

If you are certain, can you give me a few pointers on how to replace it.

Thanks

The battery is on the passenger's side in my 2000 ML 430. The noise is coming from the driver side.

Depending on the year, it's a fan noise for the climate control. It is supposed to continue to cool the interior in the summer and heat the interior in the winter after you turn the engine off. It runs approx. 5 mins. The new ML's have a switch on the dash so you can turn it on or off. The noise "bugs" me, however and I don't think that it helps much.

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

Bayer
There is a post I just replied to that may be what your problem is.
There is a small fan inside the fusebox area (drivers side) that may be your problem. It runs when the truck is running and up to 5 minutes after shutdown, same as the aux cooling pump which has been mentioned (same circuit operates both).
If this small fan gets noisy, it usually is described as a high pitched squeeling noise.

Gilly

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Yes indeed, I took the cover off yesterday and it is definitely the fan that is causing the noise.

Can this fan be lubricated, cleaned or should it be replaced?

Either way, it looks like it would not be difficult to take out. It looks like I would have to disconnect the cables that run above the fan. Should I disconnect the battery before disconnecting these wires? If not, will it cause some computer code malfunction?

Could you give me a few pointers and suggestions?

Thanks for your help.