On Tue, 07 Jul 2009 01:03:03 -0700, Usual Suspect wrote:

Maytag LSE7800.

The H & C supply lines go to the mixing valve and a single hose goes
from there to the tub. But before it connects to the tub there inserted
in the hose a plastic cube with some kind of restrictor. The cute is
open at the top. Open?

Yes, it's a 5-sided cube with no top. The water enters one side and,
apparently, flows out to the tub.

What's the name of this part?

It is not called out in these drawings:

http://snipurl.com/maytag.lse7800.diagrams

What's its purpose? It seems to be the cause of some local flooding in
the laundry room. What I thought was a cracked hose seems to be,
instead, this cube overflowing.

How does this part function and how do I determine if it needs
replacing?

Thanks,

The way to check it is to operate the machine with the washer top lifted
up. Do this very carefully!

From the information on the site you provided, it is called the water
injector assembly. It's purpose is to route water from the mixing valve
and from the recirculation pump back into the tub.

Check the in-flow path into the tub from it for deposits or restrictions
as well as be sure the machine is level. Too much powdered soap spilled
into the tub inlet will make heavy deposits that will block water flow.

If you will search for the water injector on the site provided you will
find that it is made up of about 5 different parts including gaskets
either a gasket or a hose may be damaged so you will need to inspect it
carefully for bad gaskets cracked hoses or stopped up restrictors (there
are two of them and their purpose is to keep recirculated water and fresh
separated.) or the plastic may simply have a crack that is letting water
leak out when it is under pressure.

Be sure that you check all of the hoses attached to it for cracks and
wear, they will get hard and crack in time.

It looks as if all the parts are available cheaply so replacing the
assembly in mass might be the way to go if it is really leaking.

Gnack