Water pouring sound
 

My 1994 E420 occasionally makes a sound not unlike that of pouring water. It is the strangest thing. It is coming from inside the dash. The car recently had a radiator replaced. It does not overheat and it runs fine. It has no perceptable water leaks inside or out. Just a strange pouring sound from time to time. Ideas?

Sounds like there's still a bit of air trapped in the system from the radiator replacement. It should eventually work itself out so I wouldn't worry about it too much.

You can speed the process along by running the heater on high for a while.

Water behind the dash - this is air in your lines. Follow the advice from tim down under (from another forum). I did and it fixed it.

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It has something to do with the heater hoses located in that area. Its quite possible that you have air in the lines. Have you had work done in that area?

Some owners have complained that swapping the hoses can cause this problem.

This is quite a common problem in Land Rovers; not sure whether it is the same in MB. In any event you might try this explanation and cure from Land Rover:

Most likely, air was allowed in and that's why you're hearing the coolant slosh around.

Make sure your coolant level is topped up. With the engine cold, fill the reservoir to the top. Start the engine with the reservoir cap off and let the engine warm up. At the same time, turn your heater to the highest heat level and max fan.

Run the engine with an idle speed of about 1500 to 2000 RPMS JUST for a minute or so. Doing this will cause the engine to draw in the needed coolant from the reservoir.

This should fix your water noise problem. At least for a Land Rover.

Common problem for many bands of cars. MKIII Toyota Supras are very bad about it (don't ask).

My car was so bad, the factory had a campaign to install a 'fix it kit'.

Air gets trapped in the highest place, and can't get out. This is one good reason we (at my shop) use a machine to flush, and install coolant.

A pretty good home remedy you can try, and has worked for me many times.

With a completely warm and running engine, raise the front of the car up until the muffler tips are close to hitting the ground. In other words, as high as you can. I use a drive on hoist at work, or those ramps from autoparts store. A very steep hill will do the same.

Get the radiator top way up.

Now, with the heater on high, rev the engine to 4k rpm for about 10 sec. Let off for 10 sec. Repeat 10-20x. This will help allow the air to find its way to the top of the radiator, and eventually on to the recovery tank.

It is very bad to allow the 'gurgling' to stay for long periods. The air/coolant agitation WILL eat away at the heater core and cause a leak. Leak=$$$$$$$$$$$$$$$$$$$$$$$$$$.